[PATCH 2/2] KVM: SVM: Add xsetbv intercept

Joerg Roedel
2010-12-07T16:15:42Z

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>
---
arch/x86/include/asm/svm.h | 2 ++
arch/x86/kvm/svm.c | 20 ++++++++++++++++----
2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index 11dbca7..7f3a304 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -47,6 +47,7 @@ enum {
INTERCEPT_MONITOR,
INTERCEPT_MWAIT,
INTERCEPT_MWAIT_COND,
+ INTERCEPT_XSETBV,
};

@@ -326,6 +327,7 @@ struct __attribute__ ((__packed__)) vmcb {
#define SVM_EXIT_MONITOR 0x08a
#define SVM_EXIT_MWAIT 0x08b
#define SVM_EXIT_MWAIT_COND 0x08c
+#define SVM_EXIT_XSETBV 0x08d
#define SVM_EXIT_NPF 0x400

#define SVM_EXIT_ERR -1
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 8aeda9f..4a5e584 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -904,6 +904,7 @@ 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);
@@ -2494,6 +2495,19 @@ 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);
@@ -2917,6 +2931,7 @@ 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,
};

@@ -3556,10 +3571,6 @@ 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 */
@@ -3633,6 +3644,7 @@ 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 }
};
--
1.7.1