KVM: SVM: Add xsetbv intercept

This patch implements the xsetbv intercept to the AMD part
of KVM. This makes AVX usable in a save way for the guest on
AVX capable AMD hardware.

The patch is tested by using AVX in the guest and host in
parallel and checking for data corruption. I also used the
KVM xsave unit-tests and they all pass.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 4dbc37204de1..73461b1cfb05 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -935,6 +935,7 @@ static void init_vmcb(struct vcpu_svm *svm)
         set_intercept(svm, INTERCEPT_WBINVD);
         set_intercept(svm, INTERCEPT_MONITOR);
         set_intercept(svm, INTERCEPT_MWAIT);
+        set_intercept(svm, INTERCEPT_XSETBV);
 
         control->iopm_base_pa = iopm_base;
         control->msrpm_base_pa = __pa(svm->msrpm);
@@ -2546,6 +2547,19 @@ static int skinit_interception(struct vcpu_svm *svm)
         return 1;
 }
 
+static int xsetbv_interception(struct vcpu_svm *svm)
+{
+        u64 new_bv = kvm_read_edx_eax(&svm->vcpu);
+        u32 index = kvm_register_read(&svm->vcpu, VCPU_REGS_RCX);
+
+        if (kvm_set_xcr(&svm->vcpu, index, new_bv) == 0) {
+                svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
+                skip_emulated_instruction(&svm->vcpu);
+        }
+
+        return 1;
+}
+
 static int invalid_op_interception(struct vcpu_svm *svm)
 {
         kvm_queue_exception(&svm->vcpu, UD_VECTOR);
@@ -2971,6 +2985,7 @@ static int (*svm_exit_handlers[])(struct vcpu_svm *svm) = {
         [SVM_EXIT_WBINVD]                       = emulate_on_interception,
         [SVM_EXIT_MONITOR]                      = invalid_op_interception,
         [SVM_EXIT_MWAIT]                        = invalid_op_interception,
+        [SVM_EXIT_XSETBV]                       = xsetbv_interception,
         [SVM_EXIT_NPF]                          = pf_interception,
 };
 
@@ -3624,10 +3639,6 @@ static void svm_cpuid_update(struct kvm_vcpu *vcpu)
 static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
 {
         switch (func) {
-        case 0x00000001:
-                /* Mask out xsave bit as long as it is not supported by SVM */
-                entry->ecx &= ~(bit(X86_FEATURE_XSAVE));
-                break;
         case 0x80000001:
                 if (nested)
                         entry->ecx |= (1 << 2); /* Set SVM bit */
@@ -3701,6 +3712,7 @@ static const struct trace_print_flags svm_exit_reasons_str[] = {
         { SVM_EXIT_WBINVD,                      "wbinvd" },
         { SVM_EXIT_MONITOR,                     "monitor" },
         { SVM_EXIT_MWAIT,                       "mwait" },
+        { SVM_EXIT_XSETBV,                      "xsetbv" },
         { SVM_EXIT_NPF,                         "npf" },
         { -1, NULL }
 };