| Commit message (Collapse) | Author | Age | Files | Lines |
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Right now, large folios are not supported in guest_memfd, and therefore the order
used by kvm_gmem_populate() is always 0. In this scenario, using the up-to-date
bit to track prepared-ness is nice and easy because we have one bit available
per page.
In the future, however, we might have large pages that are partially populated;
for example, in the case of SEV-SNP, if a large page has both shared and private
areas inside, it is necessary to populate it at a granularity that is smaller
than that of the guest_memfd's backing store. In that case we will have
to track preparedness at a 4K level, probably as a bitmap.
In preparation for that, do not use explicitly folio_test_uptodate() and
folio_mark_uptodate(). Return the state of the page directly from
__kvm_gmem_get_pfn(), so that it is expected to apply to 2^N pages
with N=*max_order. The function to mark a range as prepared for now
takes just a folio, but is expected to take also an index and order
(or something like that) when large pages are introduced.
Thanks to Michael Roth for pointing out the issue with large pages.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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This check is currently performed by sev_gmem_post_populate(), but it
applies to all callers of kvm_gmem_populate(): the point of the function
is that the memory is being encrypted and some work has to be done
on all the gfns in order to encrypt them.
Therefore, check the KVM_MEMORY_ATTRIBUTE_PRIVATE attribute prior
to invoking the callback, and stop the operation if a shared page
is encountered. Because CONFIG_KVM_PRIVATE_MEM in principle does
not require attributes, this makes kvm_gmem_populate() depend on
CONFIG_KVM_GENERIC_PRIVATE_MEM (which does require them).
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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While currently there is no other attribute than KVM_MEMORY_ATTRIBUTE_PRIVATE,
KVM code such as kvm_mem_is_private() is written to expect their existence.
Allow using kvm_range_has_memory_attributes() as a multi-page version of
kvm_mem_is_private(), without it breaking later when more attributes are
introduced.
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Use a guard to simplify early returns, and add two more easy
shortcuts. If the requested attributes are invalid, the attributes
xarray will never show them as set. And if testing a single page,
kvm_get_memory_attributes() is more efficient.
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Do not allow populating the same page twice with startup data. In the
case of SEV-SNP, for example, the firmware does not allow it anyway,
since the launch-update operation is only possible on pages that are
still shared in the RMP.
Even if it worked, kvm_gmem_populate()'s callback is meant to have side
effects such as updating launch measurements, and updating the same
page twice is unlikely to have the desired results.
Races between calls to the ioctl are not possible because
kvm_gmem_populate() holds slots_lock and the VM should not be running.
But again, even if this worked on other confidential computing technology,
it doesn't matter to guest_memfd.c whether this is something fishy
such as missing synchronization in userspace, or rather something
intentional. One of the racers wins, and the page is initialized by
either kvm_gmem_prepare_folio() or kvm_gmem_populate().
Anyway, out of paranoia, adjust sev_gmem_post_populate() anyway to use
the same errno that kvm_gmem_populate() is using.
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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It is enough to return 0 if a guest need not do any preparation.
This is in fact how sev_gmem_prepare() works for non-SNP guests,
and it extends naturally to Intel hosts: the x86 callback for
gmem_prepare is optional and returns 0 if not defined.
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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This is now possible because preparation is done by kvm_gmem_get_pfn()
instead of fallocate(). In practice this is not a limitation, because
even though guest_memfd can be bound to multiple struct kvm, for
hardware implementations of confidential computing only one guest
(identified by an ASID on SEV-SNP, or an HKID on TDX) will be able
to access it.
In the case of intra-host migration (not implemented yet for SEV-SNP,
but we can use SEV-ES as an idea of how it will work), the new struct
kvm inherits the same ASID and preparation need not be repeated.
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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to the guest
Initializing the contents of the folio on fallocate() is unnecessarily
restrictive. It means that the page is registered with the firmware and
then it cannot be touched anymore. In particular, this loses the
possibility of using fallocate() to pre-allocate the page for SEV-SNP
guests, because kvm_arch_gmem_prepare() then fails.
It's only when the guest actually accesses the page (and therefore
kvm_gmem_get_pfn() is called) that the page must be cleared from any
stale host data and registered with the firmware. The up-to-date flag
is clear if this has to be done (i.e. it is the first access and
kvm_gmem_populate() has not been called).
All in all, there are enough differences between kvm_gmem_get_pfn() and
kvm_gmem_populate(), that it's better to separate the two flows completely.
Extract the bulk of kvm_gmem_get_folio(), which take a folio and end up
setting its up-to-date flag, to a new function kvm_gmem_prepare_folio();
these are now done only by the non-__-prefixed kvm_gmem_get_pfn().
As a bonus, __kvm_gmem_get_pfn() loses its ugly "bool prepare" argument.
One difference is that fallocate(PUNCH_HOLE) can now race with a
page fault. Potentially this causes a page to be prepared and into the
filemap even after fallocate(PUNCH_HOLE). This is harmless, as it can be
fixed by another hole punching operation, and can be avoided by clearing
the private-page attribute prior to invoking fallocate(PUNCH_HOLE).
This way, the page fault will cause an exit to user space.
The previous semantics, where fallocate() could be used to prepare
the pages in advance of running the guest, can be accessed with
KVM_PRE_FAULT_MEMORY.
For now, accessing a page in one VM will attempt to call
kvm_arch_gmem_prepare() in all of those that have bound the guest_memfd.
Cleaning this up is left to a separate patch.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Allow testing the up-to-date flag in the caller without taking the
lock again.
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Add "ARCH" to the symbols; shortly, the "prepare" phase will include both
the arch-independent step to clear out contents left in the page by the
host, and the arch-dependent step enabled by CONFIG_HAVE_KVM_GMEM_PREPARE.
For consistency do the same for CONFIG_HAVE_KVM_GMEM_INVALIDATE as well.
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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We have a perfectly usable folio, use it to retrieve the pfn and order.
All that's needed is a version of folio_file_page that returns a pfn.
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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The up-to-date flag as is now is not too useful; it tells guest_memfd not
to overwrite the contents of a folio, but it doesn't say that the page
is ready to be mapped into the guest. For encrypted guests, mapping
a private page requires that the "preparation" phase has succeeded,
and at the same time the same page cannot be prepared twice.
So, ensure that folio_mark_uptodate() is only called on a prepared page. If
kvm_gmem_prepare_folio() or the post_populate callback fail, the folio
will not be marked up-to-date; it's not a problem to call clear_highpage()
again on such a page prior to the next preparation attempt.
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Right now this is simply more consistent and avoids use of pfn_to_page()
and put_page(). It will be put to more use in upcoming patches, to
ensure that the up-to-date flag is set at the very end of both the
kvm_gmem_get_pfn() and kvm_gmem_populate() flows.
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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KVM generic changes for 6.11
- Enable halt poll shrinking by default, as Intel found it to be a clear win.
- Setup empty IRQ routing when creating a VM to avoid having to synchronize
SRCU when creating a split IRQCHIP on x86.
- Rework the sched_in/out() paths to replace kvm_arch_sched_in() with a flag
that arch code can use for hooking both sched_in() and sched_out().
- Take the vCPU @id as an "unsigned long" instead of "u32" to avoid
truncating a bogus value from userspace, e.g. to help userspace detect bugs.
- Mark a vCPU as preempted if and only if it's scheduled out while in the
KVM_RUN loop, e.g. to avoid marking it preempted and thus writing guest
memory when retrieving guest state during live migration blackout.
- A few minor cleanups
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Add a module description for kvm.ko to fix a 'make W=1' warning:
WARNING: modpost: missing MODULE_DESCRIPTION() in arch/x86/kvm/kvm.o
Opportunistically update kvm_main.c's comically stale file comment to
match the module description.
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240622-md-kvm-v2-1-29a60f7c48b1@quicinc.com
[sean: split x86 changes to a separate commit, remove stale VT-x comment]
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Mark a vCPU as preempted/ready if-and-only-if it's scheduled out while
running. i.e. Do not mark a vCPU preempted/ready if it's scheduled out
during a non-KVM_RUN ioctl() or when userspace is doing KVM_RUN with
immediate_exit.
Commit 54aa83c90198 ("KVM: x86: do not set st->preempted when going back
to user space") stopped marking a vCPU as preempted when returning to
userspace, but if userspace then invokes a KVM vCPU ioctl() that gets
preempted, the vCPU will be marked preempted/ready. This is arguably
incorrect behavior since the vCPU was not actually preempted while the
guest was running, it was preempted while doing something on behalf of
userspace.
Marking a vCPU preempted iff its running also avoids KVM dirtying guest
memory after userspace has paused vCPUs, e.g. for live migration, which
allows userspace to collect the final dirty bitmap before or in parallel
with saving vCPU state, without having to worry about saving vCPU state
triggering writes to guest memory.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20240503181734.1467938-4-dmatlack@google.com
[sean: massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Ensure that any new KVM code that references immediate_exit gets extra
scrutiny by renaming it to immediate_exit__unsafe in kernel code.
All fields in struct kvm_run are subject to TOCTOU races since they are
mapped into userspace, which may be malicious or buggy. To protect KVM,
introduces a new macro that appends __unsafe to select field names in
struct kvm_run, hinting to developers and reviewers that accessing such
fields must be done carefully.
Apply the new macro to immediate_exit, since userspace can make
immediate_exit inconsistent with vcpu->wants_to_run, i.e. accessing
immediate_exit directly could lead to unexpected bugs in the future.
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20240503181734.1467938-3-dmatlack@google.com
[sean: massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Introduce vcpu->wants_to_run to indicate when a vCPU is in its core run
loop, i.e. when the vCPU is running the KVM_RUN ioctl and immediate_exit
was not set.
Replace all references to vcpu->run->immediate_exit with
!vcpu->wants_to_run to avoid TOCTOU races with userspace. For example, a
malicious userspace could invoked KVM_RUN with immediate_exit=true and
then after KVM reads it to set wants_to_run=false, flip it to false.
This would result in the vCPU running in KVM_RUN with
wants_to_run=false. This wouldn't cause any real bugs today but is a
dangerous landmine.
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20240503181734.1467938-2-dmatlack@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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If, on a 64 bit system, a vCPU ID is provided that has the upper 32 bits
set to a non-zero value, it may get accepted if the truncated to 32 bits
integer value is below KVM_MAX_VCPU_IDS and 'max_vcpus'. This feels very
wrong and triggered the reporting logic of PaX's SIZE_OVERFLOW plugin.
Instead of silently truncating and accepting such values, pass the full
value to kvm_vm_ioctl_create_vcpu() and make the existing limit checks
return an error.
Even if this is a userland ABI breaking change, no sane userland could
have ever relied on that behaviour.
Reported-by: PaX's SIZE_OVERFLOW plugin running on grsecurity's syzkaller
Fixes: 6aa8b732ca01 ("[PATCH] kvm: userspace interface")
Cc: Emese Revfy <re.emese@gmail.com>
Cc: PaX Team <pageexec@freemail.hu>
Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Link: https://lore.kernel.org/r/20240614202859.3597745-2-minipli@grsecurity.net
[sean: tweak comment about INT_MAX assertion]
Signed-off-by: Sean Christopherson <seanjc@google.com>
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The error path for OOM when allocating buses used to return -ENOMEM using
the local variable 'r', where 'r' was initialized at the top of the
function. But a new "r = kvm_init_irq_routing(kvm);" was introduced in
the middle of the function, so now the error code is not set and it
eventually leads to a NULL dereference due to kvm_dev_ioctl_create_vm()
thinking kvm_create_vm() succeeded. Set the error code back to -ENOMEM.
Opportunistically tweak the logic to pre-set "r = -ENOMEM" immediately
before the flows that can fail due to memory allocation failure to make
it less likely that the bug recurs in the future.
Fixes: fbe4a7e881d4 ("KVM: Setup empty IRQ routing when creating a VM")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/02051e0a-09d8-49a2-917f-7c2f278a1ba1@moroto.mountain
[sean: tweak all of the "r = -ENOMEM" sites, massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Delete kvm_arch_sched_in() now that all implementations are nops.
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20240522014013.1672962-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Add a kvm_vcpu.scheduled_out flag to track if a vCPU is in the process of
being scheduled out (vCPU put path), or if the vCPU is being reloaded
after being scheduled out (vCPU load path). In the short term, this will
allow dropping kvm_arch_sched_in(), as arch code can query scheduled_out
during kvm_arch_vcpu_load().
Longer term, scheduled_out opens up other potential optimizations, without
creating subtle/brittle dependencies. E.g. it allows KVM to keep guest
state (that is managed via kvm_arch_vcpu_{load,put}()) loaded across
kvm_sched_{out,in}(), if KVM knows the state isn't accessed by the host
kernel. Forcing arch code to coordinate between kvm_arch_sched_{in,out}()
and kvm_arch_vcpu_{load,put}() is awkward, not reusable, and relies on the
exact ordering of calls into arch code.
Adding scheduled_out also obviates the need for a kvm_arch_sched_out()
hook, e.g. if arch code needs to do something novel when putting vCPU
state.
And even if KVM never uses scheduled_out for anything beyond dropping
kvm_arch_sched_in(), just being able to remove all of the arch stubs makes
it worth adding the flag.
Link: https://lore.kernel.org/all/20240430224431.490139-1-seanjc@google.com
Cc: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20240522014013.1672962-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Setup empty IRQ routing during VM creation so that x86 and s390 don't need
to set empty/dummy IRQ routing during KVM_CREATE_IRQCHIP (in future
patches). Initializing IRQ routing before there are any potential readers
allows KVM to avoid the synchronize_srcu() in kvm_set_irq_routing(), which
can introduces 20+ milliseconds of latency in the VM creation path.
Ensuring that all VMs have non-NULL IRQ routing also hardens KVM against
misbehaving userspace VMMs, e.g. RISC-V dynamically instantiates its
interrupt controller, but doesn't override kvm_arch_intc_initialized() or
kvm_arch_irqfd_allowed(), and so can likely reach kvm_irq_map_gsi()
without fully initialized IRQ routing.
Signed-off-by: Yi Wang <foxywang@tencent.com>
Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Link: https://lore.kernel.org/r/20240506101751.3145407-2-foxywang@tencent.com
[sean: init refcount after IRQ routing, fix stub, massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Now that KVM does NOT gift async #PF workers a "struct kvm" reference,
don't bother skipping "done" workers when flushing/canceling queued
workers, as the deadlock that was being fudged around can no longer occur.
When workers, i.e. async_pf_execute(), were gifted a referenced, it was
possible for a worker to put the last reference and trigger VM destruction,
i.e. trigger flushing of a workqueue from a worker in said workqueue.
Note, there is no actual lock, the deadlock was that a worker will be
stuck waiting for itself (the workqueue code simulates a lock/unlock via
lock_map_{acquire,release}()).
Skipping "done" workers isn't problematic per se, but using work->vcpu as
a "done" flag is confusing, e.g. it's not clear that async_pf.lock is
acquired to protect the work->vcpu, NOT the processing of async_pf.queue
(which is protected by vcpu->mutex).
This reverts commit 22583f0d9c85e60c9860bc8a0ebff59fe08be6d7.
Suggested-by: Xu Yilun <yilun.xu@linux.intel.com>
Link: https://lore.kernel.org/r/20240423191649.2885257-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Default halt_poll_ns_shrink value of 0 always resets polling interval
to 0 on an un-successful poll where vcpu wakeup is not received. This is
mostly to avoid pointless polling for more number of shorter intervals. But
disabled shrink assumes vcpu wakeup is less likely to be received in
subsequent shorter polling intervals. Another side effect of 0 shrink value
is that, even on a successful poll if total block time was greater than
current polling interval, the polling interval starts over from 0 instead
of shrinking by a factor.
Enabling shrink with value of 2 allows the polling interval to gradually
decrement in case of un-successful poll events as well. This gives a fair
chance for successful polling events in subsequent polling intervals rather
than resetting it to 0 and starting over from grow_start.
Below kvm stat log snippet shows interleaved growth and shrinking of
polling interval:
87162647182125: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 10000 (grow 0)
87162647637763: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 20000 (grow 10000)
87162649627943: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 40000 (grow 20000)
87162650892407: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 20000 (shrink 40000)
87162651540378: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 40000 (grow 20000)
87162652276768: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 20000 (shrink 40000)
87162652515037: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 40000 (grow 20000)
87162653383787: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 20000 (shrink 40000)
87162653627670: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 10000 (shrink 20000)
87162653796321: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 20000 (grow 10000)
87162656171645: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 10000 (shrink 20000)
87162661607487: kvm_halt_poll_ns: vcpu 0: halt_poll_ns 0 (shrink 10000)
Having both grow and shrink enabled creates a balance in polling interval
growth and shrink behavior. Tests show improved successful polling attempt
ratio which contribute to VM performance. Power penalty is quite negligible
as shrunk polling intervals create bursts of very short durations.
Performance assessment results show 3-6% improvements in CPU+GPU, Memory
and Storage Android VM workloads whereas 5-9% improvement in average FPS of
gaming VM workloads.
Power penalty is below 1% where host OS is either idle or running a
native workload having 2 VMs enabled. CPU/GPU intensive gaming workloads
as well do not show any increased power overhead with shrink enabled.
Co-developed-by: Rajendran Jaishankar <jaishankar.rajendran@intel.com>
Signed-off-by: Rajendran Jaishankar <jaishankar.rajendran@intel.com>
Signed-off-by: Parshuram Sangle <parshuram.sangle@intel.com>
Link: https://lore.kernel.org/r/20231102154628.2120-2-parshuram.sangle@intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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After
faf01aef0570 ("KVM: PPC: Merge powerpc's debugfs entry content into generic entry")
kvm_debugfs_dir is not used anywhere else outside of kvm_main.c
Unexport it and make it static.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240515150804.9354-1-bp@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
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KVM Xen:
Fix a bug where KVM fails to check the validity of an incoming userspace
virtual address and tries to activate a gfn_to_pfn_cache with a kernel address.
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Check that the virtual address is "ok" when activating a gfn_to_pfn_cache
with a host VA to ensure that KVM never attempts to use a bad address.
This fixes a bug where KVM fails to check the incoming address when
handling KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA in kvm_xen_vcpu_set_attr().
Reported-by: syzbot+fd555292a1da3180fc82@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=fd555292a1da3180fc82
Tested-by: syzbot+fd555292a1da3180fc82@syzkaller.appspotmail.com
Signed-off-by: Pei Li <peili.dev@gmail.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/20240627-bug5-v2-1-2c63f7ee6739@gmail.com
[sean: rewrite changelog with --verbose]
Signed-off-by: Sean Christopherson <seanjc@google.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson into HEAD
LoongArch KVM changes for v6.11
1. Add ParaVirt steal time support.
2. Add some VM migration enhancement.
3. Add perf kvm-stat support for loongarch.
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KVM fixes for 6.10
- Fix a "shift too big" goof in the KVM_SEV_INIT2 selftest.
- Compute the max mappable gfn for KVM selftests on x86 using GuestMaxPhyAddr
from KVM's supported CPUID (if it's available).
- Fix a race in kvm_vcpu_on_spin() by ensuring loads and stores are atomic.
- Fix technically benign bug in __kvm_handle_hva_range() where KVM consumes
the return from a void-returning function as if it were a boolean.
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Bail from outer address space loop, not just the inner memslot loop, when
a "null" handler is encountered by __kvm_handle_hva_range(), which is the
intended behavior. On x86, which has multiple address spaces thanks to
SMM emulation, breaking from just the memslot loop results in undefined
behavior due to assigning the non-existent return value from kvm_null_fn()
to a bool.
In practice, the bug is benign as kvm_mmu_notifier_invalidate_range_end()
is the only caller that passes handler=kvm_null_fn, and it doesn't set
flush_on_ret, i.e. assigning garbage to r.ret is ultimately ignored. And
for most configuration the compiler elides the entire sequence, i.e. there
is no undefined behavior at runtime.
------------[ cut here ]------------
UBSAN: invalid-load in arch/x86/kvm/../../../virt/kvm/kvm_main.c:655:10
load of value 160 is not a valid value for type '_Bool'
CPU: 370 PID: 8246 Comm: CPU 0/KVM Not tainted 6.8.2-amdsos-build58-ubuntu-22.04+ #1
Hardware name: AMD Corporation Sh54p/Sh54p, BIOS WPC4429N 04/25/2024
Call Trace:
<TASK>
dump_stack_lvl+0x48/0x60
ubsan_epilogue+0x5/0x30
__ubsan_handle_load_invalid_value+0x79/0x80
kvm_mmu_notifier_invalidate_range_end.cold+0x18/0x4f [kvm]
__mmu_notifier_invalidate_range_end+0x63/0xe0
__split_huge_pmd+0x367/0xfc0
do_huge_pmd_wp_page+0x1cc/0x380
__handle_mm_fault+0x8ee/0xe50
handle_mm_fault+0xe4/0x4a0
__get_user_pages+0x190/0x840
get_user_pages_unlocked+0xe0/0x590
hva_to_pfn+0x114/0x550 [kvm]
kvm_faultin_pfn+0xed/0x5b0 [kvm]
kvm_tdp_page_fault+0x123/0x170 [kvm]
kvm_mmu_page_fault+0x244/0xaa0 [kvm]
vcpu_enter_guest+0x592/0x1070 [kvm]
kvm_arch_vcpu_ioctl_run+0x145/0x8a0 [kvm]
kvm_vcpu_ioctl+0x288/0x6d0 [kvm]
__x64_sys_ioctl+0x8f/0xd0
do_syscall_64+0x77/0x120
entry_SYSCALL_64_after_hwframe+0x6e/0x76
</TASK>
---[ end trace ]---
Fixes: 071064f14d87 ("KVM: Don't take mmu_lock for range invalidation unless necessary")
Signed-off-by: Babu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/b8723d39903b64c241c50f5513f804390c7b5eec.1718203311.git.babu.moger@amd.com
[sean: massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Use {READ,WRITE}_ONCE() to access kvm->last_boosted_vcpu to ensure the
loads and stores are atomic. In the extremely unlikely scenario the
compiler tears the stores, it's theoretically possible for KVM to attempt
to get a vCPU using an out-of-bounds index, e.g. if the write is split
into multiple 8-bit stores, and is paired with a 32-bit load on a VM with
257 vCPUs:
CPU0 CPU1
last_boosted_vcpu = 0xff;
(last_boosted_vcpu = 0x100)
last_boosted_vcpu[15:8] = 0x01;
i = (last_boosted_vcpu = 0x1ff)
last_boosted_vcpu[7:0] = 0x00;
vcpu = kvm->vcpu_array[0x1ff];
As detected by KCSAN:
BUG: KCSAN: data-race in kvm_vcpu_on_spin [kvm] / kvm_vcpu_on_spin [kvm]
write to 0xffffc90025a92344 of 4 bytes by task 4340 on cpu 16:
kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4112) kvm
handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel
vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:?
arch/x86/kvm/vmx/vmx.c:6606) kvm_intel
vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm
kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm
kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm
__se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890)
__x64_sys_ioctl (fs/ioctl.c:890)
x64_sys_call (arch/x86/entry/syscall_64.c:33)
do_syscall_64 (arch/x86/entry/common.c:?)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
read to 0xffffc90025a92344 of 4 bytes by task 4342 on cpu 4:
kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4069) kvm
handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel
vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:?
arch/x86/kvm/vmx/vmx.c:6606) kvm_intel
vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm
kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm
kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm
__se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890)
__x64_sys_ioctl (fs/ioctl.c:890)
x64_sys_call (arch/x86/entry/syscall_64.c:33)
do_syscall_64 (arch/x86/entry/common.c:?)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
value changed: 0x00000012 -> 0x00000000
Fixes: 217ece6129f2 ("KVM: use yield_to instead of sleep in kvm_vcpu_on_spin")
Cc: stable@vger.kernel.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20240510092353.2261824-1-leitao@debian.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Pre-population has been requested several times to mitigate KVM page faults
during guest boot or after live migration. It is also required by TDX
before filling in the initial guest memory with measured contents.
Introduce it as a generic API.
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Add a new ioctl KVM_PRE_FAULT_MEMORY in the KVM common code. It iterates on the
memory range and calls the arch-specific function. The implementation is
optional and enabled by a Kconfig symbol.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Message-ID: <819322b8f25971f2b9933bfa4506e618508ad782.1712785629.git.isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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The flags AS_UNMOVABLE and AS_INACCESSIBLE were both added just for guest_memfd;
AS_UNMOVABLE is already in existing versions of Linux, while AS_INACCESSIBLE was
acked for inclusion in 6.11.
But really, they are the same thing: only guest_memfd uses them, at least for
now, and guest_memfd pages are unmovable because they should not be
accessed by the CPU.
So merge them into one; use the AS_INACCESSIBLE name which is more comprehensive.
At the same time, this fixes an embarrassing bug where AS_INACCESSIBLE was used
as a bit mask, despite it being just a bit index.
The bug was mostly benign, because AS_INACCESSIBLE's bit representation (1010)
corresponded to setting AS_UNEVICTABLE (which is already set) and AS_ENOSPC
(except no async writes can happen on the guest_memfd). So the AS_INACCESSIBLE
flag simply had no effect.
Fixes: 1d23040caa8b ("KVM: guest_memfd: Use AS_INACCESSIBLE when creating guest_memfd inode")
Fixes: c72ceafbd12c ("mm: Introduce AS_INACCESSIBLE for encrypted/confidential memory")
Cc: linux-mm@kvack.org
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Hildenbrand <david@redhat.com>
Tested-by: Michael Roth <michael.roth@amd.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Function kvm_reset_dirty_gfn may be called with parameters cur_slot /
cur_offset / mask are all zero, it does not represent real dirty page.
It is not necessary to clear dirty page in this condition. Also return
value of macro __fls() is undefined if mask is zero which is called in
funciton kvm_reset_dirty_gfn(). Here just return.
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Message-ID: <20240613122803.1031511-1-maobibo@loongson.cn>
[Move the conditional inside kvm_reset_dirty_gfn; suggested by
Sean Christopherson. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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If kvm_gmem_get_pfn() detects an hwpoisoned page, it returns -EHWPOISON
but it does not put back the reference that kvm_gmem_get_folio() had
grabbed. Add the forgotten folio_put().
Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory")
Cc: stable@vger.kernel.org
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Some allocations done by KVM are temporary, they are created as result
of program actions, but can't exists for arbitrary long times.
They should have been GFP_TEMPORARY (rip!).
OTOH, kvm-nx-lpage-recovery and kvm-pit kernel threads exist for as long
as VM exists but their task_struct memory is not accounted.
This is story for another day.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Message-ID: <c0122f66-f428-417e-a360-b25fc0f154a0@p183>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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kvm_gmem_populate() is a potentially lengthy operation that can involve
multiple calls to the firmware. Interrupt it if a signal arrives.
Fixes: 1f6c06b177513 ("KVM: guest_memfd: Add interface for populating gmem pages with user data")
Cc: Isaku Yamahata <isaku.yamahata@intel.com>
Cc: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Pull base x86 KVM support for running SEV-SNP guests from Michael Roth:
* add some basic infrastructure and introduces a new KVM_X86_SNP_VM
vm_type to handle differences versus the existing KVM_X86_SEV_VM and
KVM_X86_SEV_ES_VM types.
* implement the KVM API to handle the creation of a cryptographic
launch context, encrypt/measure the initial image into guest memory,
and finalize it before launching it.
* implement handling for various guest-generated events such as page
state changes, onlining of additional vCPUs, etc.
* implement the gmem/mmu hooks needed to prepare gmem-allocated pages
before mapping them into guest private memory ranges as well as
cleaning them up prior to returning them to the host for use as
normal memory. Because those cleanup hooks supplant certain
activities like issuing WBINVDs during KVM MMU invalidations, avoid
duplicating that work to avoid unecessary overhead.
This merge leaves out support support for attestation guest requests
and for loading the signing keys to be used for attestation requests.
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This will handle the RMP table updates needed to put a page into a
private state before mapping it into an SEV-SNP guest.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-ID: <20240501085210.2213060-14-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Common patches for the target-independent functionality and hooks
that are needed by SEV-SNP and TDX.
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In some cases, like with SEV-SNP, guest memory needs to be updated in a
platform-specific manner before it can be safely freed back to the host.
Wire up arch-defined hooks to the .free_folio kvm_gmem_aops callback to
allow for special handling of this sort when freeing memory in response
to FALLOC_FL_PUNCH_HOLE operations and when releasing the inode, and go
ahead and define an arch-specific hook for x86 since it will be needed
for handling memory used for SEV-SNP guests.
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-Id: <20231230172351.574091-6-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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During guest run-time, kvm_arch_gmem_prepare() is issued as needed to
prepare newly-allocated gmem pages prior to mapping them into the guest.
In the case of SEV-SNP, this mainly involves setting the pages to
private in the RMP table.
However, for the GPA ranges comprising the initial guest payload, which
are encrypted/measured prior to starting the guest, the gmem pages need
to be accessed prior to setting them to private in the RMP table so they
can be initialized with the userspace-provided data. Additionally, an
SNP firmware call is needed afterward to encrypt them in-place and
measure the contents into the guest's launch digest.
While it is possible to bypass the kvm_arch_gmem_prepare() hooks so that
this handling can be done in an open-coded/vendor-specific manner, this
may expose more gmem-internal state/dependencies to external callers
than necessary. Try to avoid this by implementing an interface that
tries to handle as much of the common functionality inside gmem as
possible, while also making it generic enough to potentially be
usable/extensible for TDX as well.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Co-developed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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In preparation for adding a function that walks a set of pages
provided by userspace and populates them in a guest_memfd,
add a version of kvm_gmem_get_pfn() that has a "bool prepare"
argument and passes it down to kvm_gmem_get_folio().
Populating guest memory has to call repeatedly __kvm_gmem_get_pfn()
on the same file, so make the new function take struct file*.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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guest_memfd pages are generally expected to be in some arch-defined
initial state prior to using them for guest memory. For SEV-SNP this
initial state is 'private', or 'guest-owned', and requires additional
operations to move these pages into a 'private' state by updating the
corresponding entries the RMP table.
Allow for an arch-defined hook to handle updates of this sort, and go
ahead and implement one for x86 so KVM implementations like AMD SVM can
register a kvm_x86_ops callback to handle these updates for SEV-SNP
guests.
The preparation callback is always called when allocating/grabbing
folios via gmem, and it is up to the architecture to keep track of
whether or not the pages are already in the expected state (e.g. the RMP
table in the case of SEV-SNP).
In some cases, it is necessary to defer the preparation of the pages to
handle things like in-place encryption of initial guest memory payloads
before marking these pages as 'private'/'guest-owned'. Add an argument
(always true for now) to kvm_gmem_get_folio() that allows for the
preparation callback to be bypassed. To detect possible issues in
the way userspace initializes memory, it is only possible to add an
unprepared page if it is not already included in the filemap.
Link: https://lore.kernel.org/lkml/ZLqVdvsF11Ddo7Dq@google.com/
Co-developed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-Id: <20231230172351.574091-5-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Because kvm_gmem_get_pfn() is called from the page fault path without
any of the slots_lock, filemap lock or mmu_lock taken, it is
possible for it to race with kvm_gmem_unbind(). This is not a
problem, as any PTE that is installed temporarily will be zapped
before the guest has the occasion to run.
However, it is not possible to have a complete unbind+bind
racing with the page fault, because deleting the memslot
will call synchronize_srcu_expedited() and wait for the
page fault to be resolved. Thus, we can still warn if
the file is there and is not the one we expect.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Some SNP ioctls will require the page not to be in the pagecache, and as such they
will want to return EEXIST to userspace. Start by passing the error up from
filemap_grab_folio.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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truncate_inode_pages_range() may attempt to zero pages before truncating
them, and this will occur before arch-specific invalidations can be
triggered via .invalidate_folio/.free_folio hooks via kvm_gmem_aops. For
AMD SEV-SNP this would result in an RMP #PF being generated by the
hardware, which is currently treated as fatal (and even if specifically
allowed for, would not result in anything other than garbage being
written to guest pages due to encryption). On Intel TDX this would also
result in undesirable behavior.
Set the AS_INACCESSIBLE flag to prevent the MM from attempting
unexpected accesses of this sort during operations like truncation.
This may also in some cases yield a decent performance improvement for
guest_memfd userspace implementations that hole-punch ranges immediately
after private->shared conversions via KVM_SET_MEMORY_ATTRIBUTES, since
the current implementation of truncate_inode_pages_range() always ends
up zero'ing an entire 4K range if it is backing by a 2M folio.
Link: https://lore.kernel.org/lkml/ZR9LYhpxTaTk6PJX@google.com/
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-ID: <20240329212444.395559-6-michael.roth@amd.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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