Commit 312a1c87 authored by Aaron Lewis's avatar Aaron Lewis Committed by Paolo Bonzini
Browse files

KVM: SVM: Use wrmsr for switching between guest and host IA32_XSS on AMD 



When the guest can execute the XSAVES/XRSTORS instructions, set the
hardware IA32_XSS MSR to guest/host values on VM-entry/VM-exit.

Note that vcpu->arch.ia32_xss is currently guaranteed to be 0 on AMD,
since there is no way to change it.

Suggested-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: default avatarJim Mattson <jmattson@google.com>
Signed-off-by: default avatarAaron Lewis <aaronlewis@google.com>
Change-Id: Id51a782462086e6d7a3ab621838e200f1c005afd
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 78958563

arch/x86/kvm/svm.c

+23 −0
Original line number Diff line number Diff line
@@ -116,6 +116,8 @@ MODULE_DEVICE_TABLE(x86cpu, svm_cpu_id); 


static bool erratum_383_found __read_mostly;



static u64 __read_mostly host_xss;



static const u32 host_save_user_msrs[] = {

#ifdef CONFIG_X86_64

	MSR_STAR, MSR_LSTAR, MSR_CSTAR, MSR_SYSCALL_MASK, MSR_KERNEL_GS_BASE,
@@ -1409,6 +1411,9 @@ static __init int svm_hardware_setup(void) 
			pr_info("Virtual GIF supported\n");

	}



	if (boot_cpu_has(X86_FEATURE_XSAVES))

		rdmsrl(MSR_IA32_XSS, host_xss);



	return 0;



err:
@@ -5598,6 +5603,22 @@ static void svm_cancel_injection(struct kvm_vcpu *vcpu) 
	svm_complete_interrupts(svm);

}



static void svm_load_guest_xss(struct kvm_vcpu *vcpu)

{

	if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) &&

	    vcpu->arch.xsaves_enabled &&

	    vcpu->arch.ia32_xss != host_xss)

		wrmsrl(MSR_IA32_XSS, vcpu->arch.ia32_xss);

}



static void svm_load_host_xss(struct kvm_vcpu *vcpu)

{

	if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) &&

	    vcpu->arch.xsaves_enabled &&

	    vcpu->arch.ia32_xss != host_xss)

		wrmsrl(MSR_IA32_XSS, host_xss);

}



static void svm_vcpu_run(struct kvm_vcpu *vcpu)

{

	struct vcpu_svm *svm = to_svm(vcpu);
@@ -5637,6 +5658,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) 


	clgi();

	kvm_load_guest_xcr0(vcpu);

	svm_load_guest_xss(vcpu);



	if (lapic_in_kernel(vcpu) &&

		vcpu->arch.apic->lapic_timer.timer_advance_ns)
@@ -5786,6 +5808,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) 
	if (unlikely(svm->vmcb->control.exit_code == SVM_EXIT_NMI))

		kvm_before_interrupt(&svm->vcpu);



	svm_load_host_xss(vcpu);

	kvm_put_guest_xcr0(vcpu);

	stgi();