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

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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: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Change-Id: Id51a782462086e6d7a3ab621838e200f1c005afd
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Aaron Lewis 2019-10-21 16:30:23 -07:00 committed by Paolo Bonzini
parent 78958563d8
commit 312a1c8779
1 changed files with 23 additions and 0 deletions
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23
arch/x86/kvm/svm.c
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@ -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();