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authorLuca Tettamanti <kronos.it@gmail.com>2007-06-19 22:41:38 +0200
committerAvi Kivity <avi@qumranet.com>2007-07-16 12:05:48 +0300
commita3c870bdce4d34332ebdba7eb9969592c4c6b243 (patch)
treeea0d54e333f133a6e96a56356c5e516fc79e5580 /drivers/kvm
parent02c03a326a5df825cc01de426f72e160db2b9538 (diff)
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: Luca Tettamanti <kronos.it@gmail.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
Diffstat (limited to 'drivers/kvm')
-rw-r--r--drivers/kvm/kvm_main.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 7826f16271e5..5603000573ec 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -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);
- kvm_mmu_pte_write(vcpu, gpa, virt + offset, val, bytes);
- memcpy(virt + offset_in_page(gpa), val, bytes);
+ 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;
}