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authorJim Mattson <jmattson@google.com>2018-10-16 23:29:24 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2018-10-17 19:07:44 +0200
commitc4f55198c7c2b87909b166ffc2f6b68d9af6766c (patch)
treea3339c3e4b92009c82edf3b3016080d43db3f6a7 /Documentation/virtual
parentkvm: vmx: Defer setting of DR6 until #DB delivery (diff)
downloadlinux-c4f55198c7c2b87909b166ffc2f6b68d9af6766c.tar.xz
linux-c4f55198c7c2b87909b166ffc2f6b68d9af6766c.zip
kvm: x86: Introduce KVM_CAP_EXCEPTION_PAYLOAD
This is a per-VM capability which can be enabled by userspace so that the faulting linear address will be included with the information about a pending #PF in L2, and the "new DR6 bits" will be included with the information about a pending #DB in L2. With this capability enabled, the L1 hypervisor can now intercept #PF before CR2 is modified. Under VMX, the L1 hypervisor can now intercept #DB before DR6 and DR7 are modified. When userspace has enabled KVM_CAP_EXCEPTION_PAYLOAD, it should generally provide an appropriate payload when injecting a #PF or #DB exception via KVM_SET_VCPU_EVENTS. However, to support restoring old checkpoints, this payload is not required. Note that bit 16 of the "new DR6 bits" is set to indicate that a debug exception (#DB) or a breakpoint exception (#BP) occurred inside an RTM region while advanced debugging of RTM transactional regions was enabled. This is the reverse of DR6.RTM, which is cleared in this scenario. This capability also enables exception.pending in struct kvm_vcpu_events, which allows userspace to distinguish between pending and injected exceptions. Reported-by: Jim Mattson <jmattson@google.com> Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Jim Mattson <jmattson@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/api.txt27
1 files changed, 26 insertions, 1 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index e900ac31501c..07e87a7c665d 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4568,7 +4568,7 @@ hpage module parameter is not set to 1, -EINVAL is returned.
While it is generally possible to create a huge page backed VM without
this capability, the VM will not be able to run.
-7.14 KVM_CAP_MSR_PLATFORM_INFO
+7.15 KVM_CAP_MSR_PLATFORM_INFO
Architectures: x86
Parameters: args[0] whether feature should be enabled or not
@@ -4591,6 +4591,31 @@ state). Enabling this capability on a VM depends on the CPU having
the necessary functionality and on the facility being enabled with a
kvm-hv module parameter.
+7.17 KVM_CAP_EXCEPTION_PAYLOAD
+
+Architectures: x86
+Parameters: args[0] whether feature should be enabled or not
+
+With this capability enabled, CR2 will not be modified prior to the
+emulated VM-exit when L1 intercepts a #PF exception that occurs in
+L2. Similarly, for kvm-intel only, DR6 will not be modified prior to
+the emulated VM-exit when L1 intercepts a #DB exception that occurs in
+L2. As a result, when KVM_GET_VCPU_EVENTS reports a pending #PF (or
+#DB) exception for L2, exception.has_payload will be set and the
+faulting address (or the new DR6 bits*) will be reported in the
+exception_payload field. Similarly, when userspace injects a #PF (or
+#DB) into L2 using KVM_SET_VCPU_EVENTS, it is expected to set
+exception.has_payload and to put the faulting address (or the new DR6
+bits*) in the exception_payload field.
+
+This capability also enables exception.pending in struct
+kvm_vcpu_events, which allows userspace to distinguish between pending
+and injected exceptions.
+
+
+* For the new DR6 bits, note that bit 16 is set iff the #DB exception
+ will clear DR6.RTM.
+
8. Other capabilities.
----------------------