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KVM: SVM: Move spec control call after restore of GS 

svm_vcpu_run() invokes x86_spec_ctrl_restore_host() after VMEXIT, but
before the host GS is restored. x86_spec_ctrl_restore_host() uses 'current'
to determine the host SSBD state of the thread. 'current' is GS based, but
host GS is not yet restored and the access causes a triple fault.

Move the call after the host GS restore.

Fixes: 885f82bfbc x86/process: Allow runtime control of Speculative Store Bypass
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Thomas Gleixner 2018-05-11 15:21:01 +02:00
parent 5f2b745f5e
commit 15e6c22fd8
1 changed files with 12 additions and 12 deletions
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24
arch/x86/kvm/svm.c
View File

@ -5651,6 +5651,18 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
#endif
);
/* Eliminate branch target predictions from guest mode */
vmexit_fill_RSB();
#ifdef CONFIG_X86_64
wrmsrl(MSR_GS_BASE, svm->host.gs_base);
#else
loadsegment(fs, svm->host.fs);
#ifndef CONFIG_X86_32_LAZY_GS
loadsegment(gs, svm->host.gs);
#endif
#endif
/*
* We do not use IBRS in the kernel. If this vCPU has used the
* SPEC_CTRL MSR it may have left it on; save the value and
@ -5671,18 +5683,6 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
x86_spec_ctrl_restore_host(svm->spec_ctrl);
/* Eliminate branch target predictions from guest mode */
vmexit_fill_RSB();
#ifdef CONFIG_X86_64
wrmsrl(MSR_GS_BASE, svm->host.gs_base);
#else
loadsegment(fs, svm->host.fs);
#ifndef CONFIG_X86_32_LAZY_GS
loadsegment(gs, svm->host.gs);
#endif
#endif
reload_tss(vcpu);
local_irq_disable();