From: Avi Kivity <avi@qumranet.com>
Date: Mon, 23 Jul 2007 15:33:14 +0000 (+0300)
Subject: Revert "KVM: Avoid useless memory write when possible"
X-Git-Tag: kvm-33^0
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=b41e5014dd8712e8de2b656617f7a7a158cd992a;p=users%2Fdwmw2%2Flinux.git

Revert "KVM: Avoid useless memory write when possible"

This reverts commit 8a1449563b3e5ede56b28cc977c8da22a17cdf51.  While it
does save useless updates, it (probably) defeats the fork detector, causing
a massive performance loss.

Signed-off-by: Avi Kivity <avi@qumranet.com>
---

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 7c9bd72f74d5c..6e11871f53192 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -1085,10 +1085,8 @@ 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);
-	}
+	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;
 }