This is a note to let you know that I've just added the patch titled
KVM: nSVM: Check for NRIPS support before updating control field
to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-nsvm-check-for-nrips-support-before-updating-control-field.patch
and it can be found in the queue-4.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f104765b4f81fd74d69e0eb161e89096deade2db Mon Sep 17 00:00:00 2001
From: Bandan Das <bsd@xxxxxxxxxx>
Date: Thu, 11 Jun 2015 02:05:33 -0400
Subject: KVM: nSVM: Check for NRIPS support before updating control field
From: Bandan Das <bsd@xxxxxxxxxx>
commit f104765b4f81fd74d69e0eb161e89096deade2db upstream.
If hardware doesn't support DecodeAssist - a feature that provides
more information about the intercept in the VMCB, KVM decodes the
instruction and then updates the next_rip vmcb control field.
However, NRIP support itself depends on cpuid Fn8000_000A_EDX[NRIPS].
Since skip_emulated_instruction() doesn't verify nrip support
before accepting control.next_rip as valid, avoid writing this
field if support isn't present.
Signed-off-by: Bandan Das <bsd@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/svm.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -511,8 +511,10 @@ static void skip_emulated_instruction(st
{
struct vcpu_svm *svm = to_svm(vcpu);
- if (svm->vmcb->control.next_rip != 0)
+ if (svm->vmcb->control.next_rip != 0) {
+ WARN_ON(!static_cpu_has(X86_FEATURE_NRIPS));
svm->next_rip = svm->vmcb->control.next_rip;
+ }
if (!svm->next_rip) {
if (emulate_instruction(vcpu, EMULTYPE_SKIP) !=
@@ -4317,7 +4319,9 @@ static int svm_check_intercept(struct kv
break;
}
- vmcb->control.next_rip = info->next_rip;
+ /* TODO: Advertise NRIPS to guest hypervisor unconditionally */
+ if (static_cpu_has(X86_FEATURE_NRIPS))
+ vmcb->control.next_rip = info->next_rip;
vmcb->control.exit_code = icpt_info.exit_code;
vmexit = nested_svm_exit_handled(svm);
Patches currently in stable-queue which might be from bsd@xxxxxxxxxx are
queue-4.1/kvm-nsvm-check-for-nrips-support-before-updating-control-field.patch
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