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Commit 15e6c22f authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

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: 885f82bf x86/process: Allow runtime control of Speculative Store Bypass
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 5f2b745f

arch/x86/kvm/svm.c

+12 −12
Original line number Original line Diff line number Diff line
@@ -5651,6 +5651,18 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) 
#endif

#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

	 * 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

	 * 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);

	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);

	reload_tss(vcpu);





	local_irq_disable();

	local_irq_disable();