diff options
| author | Thomas Prescher <thomas.prescher@cyberus-technology.de> | 2024-05-08 15:25:01 +0200 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2024-06-11 18:24:31 +0200 |
| commit | 85542adb65ecd7cc0e442e8befef74f2ed07f5f6 (patch) | |
| tree | 3f270cf7ff144d486bcee57272efd1e2085ab922 /include/uapi | |
| parent | KVM: x86: Improve documentation for KVM_CAP_X86_BUS_LOCK_EXIT (diff) | |
| download | linux-85542adb65ecd7cc0e442e8befef74f2ed07f5f6.tar.xz linux-85542adb65ecd7cc0e442e8befef74f2ed07f5f6.zip | |
KVM: x86: Add KVM_RUN_X86_GUEST_MODE kvm_run flag
When a vCPU is interrupted by a signal while running a nested guest,
KVM will exit to userspace with L2 state. However, userspace has no
way to know whether it sees L1 or L2 state (besides calling
KVM_GET_STATS_FD, which does not have a stable ABI).
This causes multiple problems:
The simplest one is L2 state corruption when userspace marks the sregs
as dirty. See this mailing list thread [1] for a complete discussion.
Another problem is that if userspace decides to continue by emulating
instructions, it will unknowingly emulate with L2 state as if L1
doesn't exist, which can be considered a weird guest escape.
Introduce a new flag, KVM_RUN_X86_GUEST_MODE, in the kvm_run data
structure, which is set when the vCPU exited while running a nested
guest. Also introduce a new capability, KVM_CAP_X86_GUEST_MODE, to
advertise the functionality to userspace.
[1] https://lore.kernel.org/kvm/20240416123558.212040-1-julian.stecklina@cyberus-technology.de/T/#m280aadcb2e10ae02c191a7dc4ed4b711a74b1f55
Signed-off-by: Thomas Prescher <thomas.prescher@cyberus-technology.de>
Signed-off-by: Julian Stecklina <julian.stecklina@cyberus-technology.de>
Link: https://lore.kernel.org/r/20240508132502.184428-1-julian.stecklina@cyberus-technology.de
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'include/uapi')
| -rw-r--r-- | include/uapi/linux/kvm.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index ec998e6b6555..a6ac00ec77ad 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -918,6 +918,7 @@ struct kvm_enable_cap { #define KVM_CAP_GUEST_MEMFD 234 #define KVM_CAP_VM_TYPES 235 #define KVM_CAP_X86_APIC_BUS_CYCLES_NS 236 +#define KVM_CAP_X86_GUEST_MODE 237 struct kvm_irq_routing_irqchip { __u32 irqchip; |