On 01/13/2011 05:22 PM, Joerg Roedel wrote:
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: [email protected]
Signed-off-by: Joerg Roedel<[email protected]>
---
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
Why would an NMI crash if MSR_KERNEL_GS_BASE is bad?
I see save_paranoid depends on MSR_GS_BASE (specifically its sign, which
is bad for the new instructions that allow userspace to write gsbase),
but not on MSR_KERNEL_GS_BASE.
--
error compiling committee.c: too many arguments to function
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