Commit d835dfec authored by Avi Kivity's avatar Avi Kivity
Browse files

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



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

Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 79539cec

drivers/kvm/mmu.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

drivers/kvm/x86.c

+25 −0
Original line number Diff line number Diff line
@@ -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");

drivers/kvm/x86.h

+1 −0
Original line number Diff line number Diff line
@@ -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);