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KVM: Don't bother the mmu if cr3 load doesn't change cr3

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If the guest requests just a tlb flush, don't take the vm lock and
drop the mmu context pointlessly.

Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Avi Kivity 2007-11-21 02:57:59 +02:00
parent 79539cec0c
commit d835dfecd0
3 changed files with 27 additions and 1 deletions
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2
drivers/kvm/mmu.c
View file

@ -1086,7 +1086,7 @@ static int nonpaging_init_context(struct kvm_vcpu *vcpu)
return 0;
}
static void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu)
void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu)
{
++vcpu->stat.tlb_flush;
kvm_x86_ops->tlb_flush(vcpu);

25
drivers/kvm/x86.c
View file

@ -166,6 +166,26 @@ int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3)
return ret;
}
static bool pdptrs_changed(struct kvm_vcpu *vcpu)
{
u64 pdpte[ARRAY_SIZE(vcpu->pdptrs)];
bool changed = true;
int r;
if (is_long_mode(vcpu) || !is_pae(vcpu))
return false;
mutex_lock(&vcpu->kvm->lock);
r = kvm_read_guest(vcpu->kvm, vcpu->cr3 & ~31u, pdpte, sizeof(pdpte));
if (r < 0)
goto out;
changed = memcmp(pdpte, vcpu->pdptrs, sizeof(pdpte)) != 0;
out:
mutex_unlock(&vcpu->kvm->lock);
return changed;
}
void set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
{
if (cr0 & CR0_RESERVED_BITS) {
@ -271,6 +291,11 @@ EXPORT_SYMBOL_GPL(set_cr4);
void set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
{
if (cr3 == vcpu->cr3 && !pdptrs_changed(vcpu)) {
kvm_mmu_flush_tlb(vcpu);
return;
}
if (is_long_mode(vcpu)) {
if (cr3 & CR3_L_MODE_RESERVED_BITS) {
printk(KERN_DEBUG "set_cr3: #GP, reserved bits\n");

1
drivers/kvm/x86.h
View file

@ -299,6 +299,7 @@ int emulator_write_emulated(unsigned long addr,
unsigned long segment_base(u16 selector);
void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu);
void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
const u8 *new, int bytes);
int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva);