[3.16.y-ckt stable] Patch "KVM: nSVM: Check for NRIPS support before updating control field" has been added to staging queue
Luis Henriques
luis.henriques at canonical.com
Mon Jul 13 09:20:00 UTC 2015
This is a note to let you know that I have just added a patch titled
KVM: nSVM: Check for NRIPS support before updating control field
to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue
This patch is scheduled to be released in version 3.16.7-ckt15.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Luis
------
>From 32935497ea64ca2e6048fba57b7d76299965005f Mon Sep 17 00:00:00 2001
From: Bandan Das <bsd at redhat.com>
Date: Thu, 11 Jun 2015 02:05:33 -0400
Subject: KVM: nSVM: Check for NRIPS support before updating control field
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 at redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
arch/x86/kvm/svm.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 1c10d9071958..37e85d0a1940 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -511,8 +511,10 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
{
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) !=
@@ -4282,7 +4284,9 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu,
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);
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