On 05/20/2010 12:16 PM, Sheng Yang wrote:
From: Dexuan Cui<[email protected]>
Enable XSAVE/XRSTORE for guest.
Change from V2:
Addressed comments from Avi.
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.
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d08bb4a..3938bd1 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;
+ u64 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..a63f206 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"
@@ -247,6 +249,9 @@ static const u32 vmx_msr_index[] = {
};
#define NR_VMX_MSR ARRAY_SIZE(vmx_msr_index)
+#define MERGE_TO_U64(low, high) \
+ (((low)& -1u) | ((u64)((high)& -1u)<< 32))
+
static inline u64 kvm_read_edx_eax(vcpu) in cache_regs.h
+static int handle_xsetbv(struct kvm_vcpu *vcpu)
+{
+ u64 new_bv = MERGE_TO_U64(kvm_register_read(vcpu, VCPU_REGS_RAX),
+ kvm_register_read(vcpu, VCPU_REGS_RDX));
+
+ if (kvm_register_read(vcpu, VCPU_REGS_RCX) != 0)
+ goto err;
+ if (vmx_get_cpl(vcpu) != 0)
+ goto err;
+ if (!(new_bv& XSTATE_FP))
+ goto err;
+ if ((new_bv& XSTATE_YMM)&& !(new_bv& XSTATE_SSE))
+ goto err;
What about a check against unknown bits?
+ 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;
+static u64 host_xcr0;
__read_mostly.
+
+static void update_cpuid(struct kvm_vcpu *vcpu)
+{
+ struct kvm_cpuid_entry2 *best;
+
+ best = kvm_find_cpuid_entry(vcpu, 1, 0);
+ if (!best)
+ return;
+
+ /* 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);
+ }
+}
Note: need to update after userspace writes cpuid as well.
+
int __kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
unsigned long old_cr4 = kvm_read_cr4(vcpu);
@@ -481,6 +513,9 @@ int __kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
if (cr4& CR4_RESERVED_BITS)
return 1;
+ if (!guest_cpuid_has_xsave(vcpu)&& (cr4& X86_CR4_OSXSAVE))
+ return 1;
+
if (is_long_mode(vcpu)) {
if (!(cr4& X86_CR4_PAE))
return 1;
@@ -497,6 +532,9 @@ int __kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
if ((cr4 ^ old_cr4)& pdptr_bits)
kvm_mmu_reset_context(vcpu);
+ if ((cr4 ^ old_cr4)& X86_CR4_OSXSAVE)
+ update_cpuid(vcpu);
+
I think we need to reload the guest's xcr0 at this point.
Alternatively, call vmx_load_host_state() to ensure the the next entry
will reload it.
@@ -1931,7 +1964,7 @@ 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);
Do we need any special handling for leaf 0xc?
@@ -4567,6 +4616,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
kvm_x86_ops->prepare_guest_switch(vcpu);
if (vcpu->fpu_active)
kvm_load_guest_fpu(vcpu);
+ if (kvm_read_cr4(vcpu)& X86_CR4_OSXSAVE)
+ xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);
Better done in vmx_save_host_state(), so we only do it on context
switches or entries from userspace.
kvm_read_cr4_bits() is faster - doesn't need a vmcs_readl().
atomic_set(&vcpu->guest_mode, 1);
smp_wmb();
@@ -5118,6 +5169,10 @@ void fx_init(struct kvm_vcpu *vcpu)
fpu_alloc(&vcpu->arch.guest_fpu);
fpu_finit(&vcpu->arch.guest_fpu);
+ /* Ensure guest xcr0 is valid for loading */
+ if (cpu_has_xsave)
+ vcpu->arch.xcr0 = XSTATE_FP;
+
Can do it unconditionally, not that it matters much.
void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
{
if (vcpu->guest_fpu_loaded)
@@ -5134,6 +5197,10 @@ void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
vcpu->guest_fpu_loaded = 1;
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));
Best to calculate it out of the fast path, when guest cpuid is set.
Need to check it at this time as well.
Also can avoid it if guest xcr0 == host xcr0.
fpu_restore_checking(&vcpu->arch.guest_fpu);
trace_kvm_fpu(1);
}
@@ -5144,7 +5211,14 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
return;
vcpu->guest_fpu_loaded = 0;
+ /* 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));
Ditto.
fpu_save_init(&vcpu->arch.guest_fpu);
+ if (cpu_has_xsave)
+ xsetbv(XCR_XFEATURE_ENABLED_MASK,
+ host_xcr0);
++vcpu->stat.fpu_reload;
set_bit(KVM_REQ_DEACTIVATE_FPU,&vcpu->requests);
trace_kvm_fpu(0);
--
Do not meddle in the internals of kernels, for they are subtle and quick to
panic.
--
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