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Revert "KVM: SVM: fix trashing of MSR_TSC_AUX"
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This reverts commit 9770404.

The reverted patch is not needed as only userspace uses RDTSCP and
MSR_TSC_AUX is in host_save_user_msrs[] and therefore properly saved in
svm_vcpu_load() and restored in svm_vcpu_put() before every switch to
userspace.

The reverted patch did not allow the kernel to use RDTSCP in the future,
because of missed trashing in svm_set_msr() and 64-bit ifdef.

This reverts commit 2b23c3a.

2b23c3a ("KVM: SVM: do not set MSR_TSC_AUX on 32-bit builds") is a
build fix for 9770404 and reverting them separately would only
break more bisections.

Cc: stable@vger.kernel.org
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Radim Krčmář committed Jul 16, 2016
1 parent 2b23c3a commit 6a907cd
Showing 1 changed file with 3 additions and 5 deletions.
8 changes: 3 additions & 5 deletions arch/x86/kvm/svm.c
Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,6 @@
#include <asm/desc.h>
#include <asm/debugreg.h>
#include <asm/kvm_para.h>
#include <asm/vgtod.h>

#include <asm/virtext.h>
#include "trace.h"
Expand Down Expand Up @@ -1531,6 +1530,9 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
wrmsrl(MSR_AMD64_TSC_RATIO, tsc_ratio);
}
}
/* This assumes that the kernel never uses MSR_TSC_AUX */
if (static_cpu_has(X86_FEATURE_RDTSCP))
wrmsrl(MSR_TSC_AUX, svm->tsc_aux);

avic_vcpu_load(vcpu, cpu);
}
Expand Down Expand Up @@ -4472,8 +4474,6 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
svm->vmcb->save.cr2 = vcpu->arch.cr2;

clgi();
if (static_cpu_has(X86_FEATURE_RDTSCP))
wrmsrl(MSR_TSC_AUX, svm->tsc_aux);

local_irq_enable();

Expand Down Expand Up @@ -4551,8 +4551,6 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
);

#ifdef CONFIG_X86_64
if (static_cpu_has(X86_FEATURE_RDTSCP))
wrmsrl(MSR_TSC_AUX, __getcpu());
wrmsrl(MSR_GS_BASE, svm->host.gs_base);
#else
loadsegment(fs, svm->host.fs);
Expand Down

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