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KVM: x86: only copy XSAVE state for the supported features 

This makes the interface more deterministic for userspace, which can expect
(after configuring only the features it supports) to get exactly the same
state from the kernel, independent of the host CPU and kernel version.

Suggested-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
This commit is contained in:
Paolo Bonzini 2013-10-02 16:06:16 +02:00 committed by Gleb Natapov
parent d7876f1be4
commit 4344ee981e
3 changed files with 34 additions and 6 deletions
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1
arch/x86/include/asm/kvm_host.h
View File

@ -390,6 +390,7 @@ struct kvm_vcpu_arch {
struct fpu guest_fpu;
u64 xcr0;
u64 guest_supported_xcr0;
u32 guest_xstate_size;
struct kvm_pio_request pio;
void *pio_data;

28
arch/x86/kvm/cpuid.c
View File

@ -23,6 +23,26 @@
#include "mmu.h"
#include "trace.h"
static u32 xstate_required_size(u64 xstate_bv)
{
int feature_bit = 0;
u32 ret = XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET;
xstate_bv &= ~XSTATE_FPSSE;
while (xstate_bv) {
if (xstate_bv & 0x1) {
u32 eax, ebx, ecx, edx;
cpuid_count(0xD, feature_bit, &eax, &ebx, &ecx, &edx);
ret = max(ret, eax + ebx);
}
xstate_bv >>= 1;
feature_bit++;
}
return ret;
}
void kvm_update_cpuid(struct kvm_vcpu *vcpu)
{
struct kvm_cpuid_entry2 *best;
@ -47,12 +67,16 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
}
best = kvm_find_cpuid_entry(vcpu, 0xD, 0);
if (!best)
if (!best) {
vcpu->arch.guest_supported_xcr0 = 0;
else
vcpu->arch.guest_xstate_size = XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET;
} else {
vcpu->arch.guest_supported_xcr0 =
(best->eax | ((u64)best->edx << 32)) &
host_xcr0 & KVM_SUPPORTED_XCR0;
vcpu->arch.guest_xstate_size =
xstate_required_size(vcpu->arch.guest_supported_xcr0);
}
kvm_pmu_cpuid_update(vcpu);
}

11
arch/x86/kvm/x86.c
View File

@ -2984,11 +2984,13 @@ static int kvm_vcpu_ioctl_x86_set_debugregs(struct kvm_vcpu *vcpu,
static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu,
struct kvm_xsave *guest_xsave)
{
if (cpu_has_xsave)
if (cpu_has_xsave) {
memcpy(guest_xsave->region,
&vcpu->arch.guest_fpu.state->xsave,
xstate_size);
else {
vcpu->arch.guest_xstate_size);
*(u64 *)&guest_xsave->region[XSAVE_HDR_OFFSET / sizeof(u32)] &=
vcpu->arch.guest_supported_xcr0 | XSTATE_FPSSE;
} else {
memcpy(guest_xsave->region,
&vcpu->arch.guest_fpu.state->fxsave,
sizeof(struct i387_fxsave_struct));
@ -3014,7 +3016,7 @@ static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,
if (xstate_bv & ~host_xcr0)
return -EINVAL;
memcpy(&vcpu->arch.guest_fpu.state->xsave,
guest_xsave->region, xstate_size);
guest_xsave->region, vcpu->arch.guest_xstate_size);
} else {
if (xstate_bv & ~XSTATE_FPSSE)
return -EINVAL;
@ -6951,6 +6953,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
vcpu->arch.pv_time_enabled = false;
vcpu->arch.guest_supported_xcr0 = 0;
vcpu->arch.guest_xstate_size = XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET;
kvm_async_pf_hash_reset(vcpu);
kvm_pmu_init(vcpu);