KVM: VMX: Use wrmsr for switching between guest and host IA32_XSS on Intel

When the guest can execute the XSAVES/XRSTORS instructions, use wrmsr to
set the hardware IA32_XSS MSR to guest/host values on VM-entry/VM-exit,
rather than the MSR-load areas. By using the same approach as AMD, we
will be able to use a common implementation for both (in the next
patch).

Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Change-Id: I9447d104b2615c04e39e4af0c911e1e7309bf464
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e5b09c7..aee6f1a 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2081,13 +2081,6 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
                if (data != 0)
                        return 1;
                vcpu->arch.ia32_xss = data;
-               if (vcpu->arch.xsaves_enabled) {
-                       if (vcpu->arch.ia32_xss != host_xss)
-                               add_atomic_switch_msr(vmx, MSR_IA32_XSS,
-                                       vcpu->arch.ia32_xss, host_xss, false);
-                       else
-                               clear_atomic_switch_msr(vmx, MSR_IA32_XSS);
-               }
                break;
        case MSR_IA32_RTIT_CTL:
                if ((pt_mode != PT_MODE_HOST_GUEST) ||
@@ -6473,6 +6466,22 @@ void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
        }
 }
 
+static void vmx_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 vmx_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);
+}
+
 bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs, bool launched);
 
 static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
@@ -6524,6 +6533,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
                vmx_set_interrupt_shadow(vcpu, 0);
 
        kvm_load_guest_xcr0(vcpu);
+       vmx_load_guest_xss(vcpu);
 
        if (static_cpu_has(X86_FEATURE_PKU) &&
            kvm_read_cr4_bits(vcpu, X86_CR4_PKE) &&
@@ -6630,6 +6640,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
                        __write_pkru(vmx->host_pkru);
        }
 
+       vmx_load_host_xss(vcpu);
        kvm_put_guest_xcr0(vcpu);
 
        vmx->nested.nested_run_pending = 0;