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Commit a3c870bd authored by Luca Tettamanti's avatar Luca Tettamanti Committed by Avi Kivity
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KVM: Avoid useless memory write when possible 



When writing to normal memory and the memory area is unchanged the write
can be safely skipped, avoiding the costly kvm_mmu_pte_write.

Signed-Off-By: default avatarLuca Tettamanti <kronos.it@gmail.com>
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 02c03a32

drivers/kvm/kvm_main.c

+4 −2
Original line number Diff line number Diff line
@@ -1170,8 +1170,10 @@ static int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa, 
		return 0;

	mark_page_dirty(vcpu->kvm, gpa >> PAGE_SHIFT);

	virt = kmap_atomic(page, KM_USER0);

	if (memcmp(virt + offset_in_page(gpa), val, bytes)) {

		kvm_mmu_pte_write(vcpu, gpa, virt + offset, val, bytes);

		memcpy(virt + offset_in_page(gpa), val, bytes);

	}

	kunmap_atomic(virt, KM_USER0);

	return 1;

}