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KVM: Fetch guest cr3 from hardware on demand
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Instead of syncing the guest cr3 every exit, which is expensince on vmx
with ept enabled, sync it only on demand.

[sheng: fix incorrect cr3 seen by Windows XP]

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
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Avi Kivity committed Jan 12, 2011
1 parent 9f8fe50 commit aff48ba
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Showing 5 changed files with 23 additions and 6 deletions.
2 changes: 2 additions & 0 deletions arch/x86/include/asm/kvm_host.h
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Original file line number Diff line number Diff line change
Expand Up @@ -117,6 +117,7 @@ enum kvm_reg {

enum kvm_reg_ex {
VCPU_EXREG_PDPTR = NR_VCPU_REGS,
VCPU_EXREG_CR3,
};

enum {
Expand Down Expand Up @@ -533,6 +534,7 @@ struct kvm_x86_ops {
struct kvm_segment *var, int seg);
void (*get_cs_db_l_bits)(struct kvm_vcpu *vcpu, int *db, int *l);
void (*decache_cr0_guest_bits)(struct kvm_vcpu *vcpu);
void (*decache_cr3)(struct kvm_vcpu *vcpu);
void (*decache_cr4_guest_bits)(struct kvm_vcpu *vcpu);
void (*set_cr0)(struct kvm_vcpu *vcpu, unsigned long cr0);
void (*set_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3);
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2 changes: 2 additions & 0 deletions arch/x86/kvm/kvm_cache_regs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,8 @@ static inline ulong kvm_read_cr4_bits(struct kvm_vcpu *vcpu, ulong mask)

static inline ulong kvm_read_cr3(struct kvm_vcpu *vcpu)
{
if (!test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail))
kvm_x86_ops->decache_cr3(vcpu);
return vcpu->arch.cr3;
}

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5 changes: 5 additions & 0 deletions arch/x86/kvm/svm.c
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Expand Up @@ -1327,6 +1327,10 @@ static void svm_decache_cr0_guest_bits(struct kvm_vcpu *vcpu)
{
}

static void svm_decache_cr3(struct kvm_vcpu *vcpu)
{
}

static void svm_decache_cr4_guest_bits(struct kvm_vcpu *vcpu)
{
}
Expand Down Expand Up @@ -3871,6 +3875,7 @@ static struct kvm_x86_ops svm_x86_ops = {
.get_cpl = svm_get_cpl,
.get_cs_db_l_bits = kvm_get_cs_db_l_bits,
.decache_cr0_guest_bits = svm_decache_cr0_guest_bits,
.decache_cr3 = svm_decache_cr3,
.decache_cr4_guest_bits = svm_decache_cr4_guest_bits,
.set_cr0 = svm_set_cr0,
.set_cr3 = svm_set_cr3,
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18 changes: 12 additions & 6 deletions arch/x86/kvm/vmx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -180,6 +180,7 @@ static int init_rmode(struct kvm *kvm);
static u64 construct_eptp(unsigned long root_hpa);
static void kvm_cpu_vmxon(u64 addr);
static void kvm_cpu_vmxoff(void);
static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3);

static DEFINE_PER_CPU(struct vmcs *, vmxarea);
static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
Expand Down Expand Up @@ -1866,6 +1867,13 @@ static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu)
vcpu->arch.cr0 |= vmcs_readl(GUEST_CR0) & cr0_guest_owned_bits;
}

static void vmx_decache_cr3(struct kvm_vcpu *vcpu)
{
if (enable_ept && is_paging(vcpu))
vcpu->arch.cr3 = vmcs_readl(GUEST_CR3);
__set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);
}

static void vmx_decache_cr4_guest_bits(struct kvm_vcpu *vcpu)
{
ulong cr4_guest_owned_bits = vcpu->arch.cr4_guest_owned_bits;
Expand Down Expand Up @@ -1909,6 +1917,7 @@ static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
unsigned long cr0,
struct kvm_vcpu *vcpu)
{
vmx_decache_cr3(vcpu);
if (!(cr0 & X86_CR0_PG)) {
/* From paging/starting to nonpaging */
vmcs_write32(CPU_BASED_VM_EXEC_CONTROL,
Expand Down Expand Up @@ -3756,11 +3765,6 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
if (vmx->emulation_required && emulate_invalid_guest_state)
return handle_invalid_guest_state(vcpu);

/* Access CR3 don't cause VMExit in paging mode, so we need
* to sync with guest real CR3. */
if (enable_ept && is_paging(vcpu))
vcpu->arch.cr3 = vmcs_readl(GUEST_CR3);

if (exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) {
vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
vcpu->run->fail_entry.hardware_entry_failure_reason
Expand Down Expand Up @@ -4077,7 +4081,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
);

vcpu->arch.regs_avail = ~((1 << VCPU_REGS_RIP) | (1 << VCPU_REGS_RSP)
| (1 << VCPU_EXREG_PDPTR));
| (1 << VCPU_EXREG_PDPTR)
| (1 << VCPU_EXREG_CR3));
vcpu->arch.regs_dirty = 0;

vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
Expand Down Expand Up @@ -4344,6 +4349,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
.get_cpl = vmx_get_cpl,
.get_cs_db_l_bits = vmx_get_cs_db_l_bits,
.decache_cr0_guest_bits = vmx_decache_cr0_guest_bits,
.decache_cr3 = vmx_decache_cr3,
.decache_cr4_guest_bits = vmx_decache_cr4_guest_bits,
.set_cr0 = vmx_set_cr0,
.set_cr3 = vmx_set_cr3,
Expand Down
2 changes: 2 additions & 0 deletions arch/x86/kvm/x86.c
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Original file line number Diff line number Diff line change
Expand Up @@ -667,6 +667,7 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
if (unlikely(!gfn_to_memslot(vcpu->kvm, cr3 >> PAGE_SHIFT)))
return 1;
vcpu->arch.cr3 = cr3;
__set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);
vcpu->arch.mmu.new_cr3(vcpu);
return 0;
}
Expand Down Expand Up @@ -5583,6 +5584,7 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
vcpu->arch.cr2 = sregs->cr2;
mmu_reset_needed |= kvm_read_cr3(vcpu) != sregs->cr3;
vcpu->arch.cr3 = sregs->cr3;
__set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);

kvm_set_cr8(vcpu, sregs->cr8);

Expand Down

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