[PATCH v2] KVM: VMX: Enable XSAVE/XRSTORE for guest

Sheng Yang
2010-05-19T08:37:43Z

From: Dexuan Cui <dexuan.cui@intel.com>

Enable XSAVE/XRSTORE for guest.

Change from V1:

1. Use FPU API.
2. Fix CPUID issue.
3. Save/restore all possible guest xstate fields when switching. Because we
don't know which fields guest has already touched.

Signed-off-by: Dexuan Cui <dexuan.cui@intel.com>
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/include/asm/vmx.h | 1 +
arch/x86/kvm/vmx.c | 28 +++++++++++++
arch/x86/kvm/x86.c | 85 +++++++++++++++++++++++++++++++++++---
4 files changed, 108 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d08bb4a..78d7b06 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -302,6 +302,7 @@ struct kvm_vcpu_arch {
} update_pte;

struct fpu guest_fpu;
+ uint64_t xcr0, host_xcr0;

gva_t mmio_fault_cr2;
struct kvm_pio_request pio;
diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 9e6779f..346ea66 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -266,6 +266,7 @@ enum vmcs_field {
#define EXIT_REASON_EPT_VIOLATION 48
#define EXIT_REASON_EPT_MISCONFIG 49
#define EXIT_REASON_WBINVD 54
+#define EXIT_REASON_XSETBV 55

/*
* Interruption-information format
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 99ae513..2ee8ff6 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -36,6 +36,8 @@
#include <asm/vmx.h>
#include <asm/virtext.h>
#include <asm/mce.h>
+#include <asm/i387.h>
+#include <asm/xcr.h>

#include "trace.h"

@@ -2616,6 +2618,8 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
vmx->vcpu.arch.cr4_guest_owned_bits = KVM_CR4_GUEST_OWNED_BITS;
if (enable_ept)
vmx->vcpu.arch.cr4_guest_owned_bits |= X86_CR4_PGE;
+ if (cpu_has_xsave)
+ vmx->vcpu.arch.cr4_guest_owned_bits |= X86_CR4_OSXSAVE;
vmcs_writel(CR4_GUEST_HOST_MASK, ~vmx->vcpu.arch.cr4_guest_owned_bits);

tsc_base = vmx->vcpu.kvm->arch.vm_init_tsc;
@@ -3354,6 +3358,29 @@ static int handle_wbinvd(struct kvm_vcpu *vcpu)
return 1;
}

+static int handle_xsetbv(struct kvm_vcpu *vcpu)
+{
+ u64 new_bv = ((u64)(kvm_register_read(vcpu, VCPU_REGS_RDX) << 32)) |
+ kvm_register_read(vcpu, VCPU_REGS_RAX);
+
+ if (kvm_register_read(vcpu, VCPU_REGS_RCX) != 0)
+ goto err;
+ if (vmx_get_cpl(vcpu) != 0)
+ goto err;
+ if (!(new_bv & XSTATE_FP) ||
+ (new_bv & ~vcpu->arch.host_xcr0))
+ goto err;
+ if ((new_bv & XSTATE_YMM) && !(new_bv & XSTATE_SSE))
+ goto err;
+ vcpu->arch.xcr0 = new_bv;
+ xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);
+ skip_emulated_instruction(vcpu);
+ return 1;
+err:
+ kvm_inject_gp(vcpu, 0);
+ return 1;
+}
+
static int handle_apic_access(struct kvm_vcpu *vcpu)
{
return emulate_instruction(vcpu, 0, 0, 0) == EMULATE_DONE;
@@ -3632,6 +3659,7 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
[EXIT_REASON_TPR_BELOW_THRESHOLD] = handle_tpr_below_threshold,
[EXIT_REASON_APIC_ACCESS] = handle_apic_access,
[EXIT_REASON_WBINVD] = handle_wbinvd,
+ [EXIT_REASON_XSETBV] = handle_xsetbv,
[EXIT_REASON_TASK_SWITCH] = handle_task_switch,
[EXIT_REASON_MCE_DURING_VMENTRY] = handle_machine_check,
[EXIT_REASON_EPT_VIOLATION] = handle_ept_violation,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7be1d36..5e20f37 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -64,6 +64,7 @@
(~(unsigned long)(X86_CR4_VME | X86_CR4_PVI | X86_CR4_TSD | X86_CR4_DE\
| X86_CR4_PSE | X86_CR4_PAE | X86_CR4_MCE \
| X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR \
+ | X86_CR4_OSXSAVE \
| X86_CR4_OSXMMEXCPT | X86_CR4_VMXE))

#define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR)
@@ -149,6 +150,11 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{ NULL }
};

+static inline u32 bit(int bitno)
+{
+ return 1 << (bitno & 31);
+}
+
static void kvm_on_user_return(struct user_return_notifier *urn)
{
unsigned slot;
@@ -473,6 +479,17 @@ void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw)
}
EXPORT_SYMBOL_GPL(kvm_lmsw);

+static bool guest_cpuid_has_xsave(struct kvm_vcpu *vcpu)
+{
+ struct kvm_cpuid_entry2 *best;
+
+ best = kvm_find_cpuid_entry(vcpu, 1, 0);
+ if (best->ecx & bit(X86_FEATURE_XSAVE))
+ return true;
+
+ return false;
+}
+
int __kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
unsigned long old_cr4 = kvm_read_cr4(vcpu);
@@ -481,6 +498,9 @@ int __kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
if (cr4 & CR4_RESERVED_BITS)
return 1;

+ if (!guest_cpuid_has_xsave(vcpu) && X86_CR4_OSXSAVE)
+ return 1;
+
if (is_long_mode(vcpu)) {
if (!(cr4 & X86_CR4_PAE))
return 1;
@@ -665,11 +685,6 @@ int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
}
EXPORT_SYMBOL_GPL(kvm_get_dr);

-static inline u32 bit(int bitno)
-{
- return 1 << (bitno & 31);
-}
-
/*
* List of msr numbers which we expose to userspace through KVM_GET_MSRS
* and KVM_SET_MSRS, and KVM_GET_MSR_INDEX_LIST.
@@ -1887,6 +1902,7 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
unsigned f_lm = 0;
#endif
unsigned f_rdtscp = kvm_x86_ops->rdtscp_supported() ? F(RDTSCP) : 0;
+ unsigned f_xsave = cpu_has_xsave ? F(XSAVE) : 0;

/* cpuid 1.edx */
const u32 kvm_supported_word0_x86_features =
@@ -1916,7 +1932,7 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
0 /* Reserved */ | F(CX16) | 0 /* xTPR Update, PDCM */ |
0 /* Reserved, DCA */ | F(XMM4_1) |
F(XMM4_2) | F(X2APIC) | F(MOVBE) | F(POPCNT) |
- 0 /* Reserved, XSAVE, OSXSAVE */;
+ 0 /* Reserved, AES */ | f_xsave | 0 /* OSXSAVE */;
/* cpuid 0x80000001.ecx */
const u32 kvm_supported_word6_x86_features =
F(LAHF_LM) | F(CMP_LEGACY) | F(SVM) | 0 /* ExtApicSpace */ |
@@ -1931,7 +1947,7 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,

switch (function) {
case 0:
- entry->eax = min(entry->eax, (u32)0xb);
+ entry->eax = min(entry->eax, (u32)0xd);
break;
case 1:
entry->edx &= kvm_supported_word0_x86_features;
@@ -1989,6 +2005,20 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
}
break;
}
+ case 0xd: {
+ int i;
+
+ entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
+ for (i = 1; *nent < maxnent; ++i) {
+ if (entry[i - 1].eax == 0 && i != 2)
+ break;
+ do_cpuid_1_ent(&entry[i], function, i);
+ entry[i].flags |=
+ KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
+ ++*nent;
+ }
+ break;
+ }
case KVM_CPUID_SIGNATURE: {
char signature[12] = "KVMKVMKVM\0\0";
u32 *sigptr = (u32 *)signature;
@@ -4376,6 +4406,17 @@ not_found:
return 36;
}

+static void kvm_update_cpuid(struct kvm_vcpu *vcpu,
+ struct kvm_cpuid_entry2 *best)
+{
+ /* Update OSXSAVE bit */
+ if (cpu_has_xsave && best->function == 0x1) {
+ best->ecx &= ~(bit(X86_FEATURE_OSXSAVE));
+ if (kvm_read_cr4(vcpu) & X86_CR4_OSXSAVE)
+ best->ecx |= bit(X86_FEATURE_OSXSAVE);
+ }
+}
+
void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
{
u32 function, index;
@@ -4389,6 +4430,7 @@ void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
kvm_register_write(vcpu, VCPU_REGS_RDX, 0);
best = kvm_find_cpuid_entry(vcpu, function, index);
if (best) {
+ kvm_update_cpuid(vcpu, best);
kvm_register_write(vcpu, VCPU_REGS_RAX, best->eax);
kvm_register_write(vcpu, VCPU_REGS_RBX, best->ebx);
kvm_register_write(vcpu, VCPU_REGS_RCX, best->ecx);
@@ -5118,6 +5160,11 @@ void fx_init(struct kvm_vcpu *vcpu)
fpu_alloc(&vcpu->arch.guest_fpu);
fpu_finit(&vcpu->arch.guest_fpu);

+ if (cpu_has_xsave) {
+ vcpu->arch.host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
+ vcpu->arch.xcr0 = vcpu->arch.host_xcr0;
+ }
+
vcpu->arch.cr0 |= X86_CR0_ET;
}
EXPORT_SYMBOL_GPL(fx_init);
@@ -5127,14 +5174,30 @@ static void fx_free(struct kvm_vcpu *vcpu)
fpu_free(&vcpu->arch.guest_fpu);
}

+static u64 cpuid_get_possible_xcr0(struct kvm_vcpu *vcpu)
+{
+ unsigned int eax, ebx, ecx, edx;
+
+ cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
+ return eax + ((u64)edx << 32);
+}
+
void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
{
if (vcpu->guest_fpu_loaded)
return;

vcpu->guest_fpu_loaded = 1;
+ if (cpu_has_xsave)
+ vcpu->arch.host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
unlazy_fpu(current);
+ /* Restore all possible states in the guest */
+ if (cpu_has_xsave && guest_cpuid_has_xsave(vcpu))
+ xsetbv(XCR_XFEATURE_ENABLED_MASK,
+ cpuid_get_possible_xcr0(vcpu));
fpu_restore_checking(&vcpu->arch.guest_fpu);
+ if (cpu_has_xsave)
+ xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);
trace_kvm_fpu(1);
}

@@ -5144,7 +5207,15 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
return;

vcpu->guest_fpu_loaded = 0;
+ if (cpu_has_xsave)
+ vcpu->arch.xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
+ /* Save all possible states in the guest */
+ if (cpu_has_xsave && guest_cpuid_has_xsave(vcpu))
+ xsetbv(XCR_XFEATURE_ENABLED_MASK,
+ cpuid_get_possible_xcr0(vcpu));
fpu_save_init(&vcpu->arch.guest_fpu);
+ if (cpu_has_xsave)
+ xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.host_xcr0);
++vcpu->stat.fpu_reload;
set_bit(KVM_REQ_DEACTIVATE_FPU, &vcpu->requests);
trace_kvm_fpu(0);
--
1.7.0.1