[PATCH 1/2] KVM: SVM: Fix NMI path when NMI happens in guest mode

[Joerg Roedel <joerg.roedel@amd.com>]

The vmexit path on SVM needs to restore the KERNEL_GS_BASE
MSR in order to savely execute the NMI handler. Otherwise a
pending NMI can occur after the STGI instruction and crash
the machine.
This makes it impossible to run perf and kvm in parallel on
an AMD machine in a stable way.

Cc: stable@kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
---
 arch/x86/kvm/svm.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 25bd1bc..8b9bc72 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3637,6 +3637,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
 
 #ifdef CONFIG_X86_64
 	wrmsrl(MSR_GS_BASE, svm->host.gs_base);
+	wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gs);
 #else
 	loadsegment(fs, svm->host.fs);
 #endif
-- 
1.7.1