commit 4a5f48f666ccc4ffdbc54241d9cab06806ed7922
author Avi Kivity <avi@redhat.com> Mon Mar 15 13:59:55 2010 +0200
committer Avi Kivity <avi@redhat.com> Mon May 17 12:15:40 2010 +0300
tree 91a1851ad84d2380a5cb9c1e9223d44ffc87365e
parent daea3e73cb4ac971bee97f333ae027861d00fc0b

KVM: Don't follow an atomic operation by a non-atomic one

Currently emulated atomic operations are immediately followed by a non-atomic
operation, so that kvm_mmu_pte_write() can be invoked.  This updates the mmu
but undoes the whole point of doing things atomically.

Fix by only performing the atomic operation and the mmu update, and avoiding
the non-atomic write.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/x86.c

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 855f3ea..dd4a7ad 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3234,7 +3234,8 @@
 static int emulator_write_emulated_onepage(unsigned long addr,
 					   const void *val,
 					   unsigned int bytes,
-					   struct kvm_vcpu *vcpu)
+					   struct kvm_vcpu *vcpu,
+					   bool mmu_only)
 {
 	gpa_t                 gpa;
 	u32 error_code;
@@ -3250,6 +3251,10 @@
 	if ((gpa & PAGE_MASK) == APIC_DEFAULT_PHYS_BASE)
 		goto mmio;
 
+	if (mmu_only) {
+		kvm_mmu_pte_write(vcpu, gpa, val, bytes, 1);
+		return X86EMUL_CONTINUE;
+	}
 	if (emulator_write_phys(vcpu, gpa, val, bytes))
 		return X86EMUL_CONTINUE;
 
@@ -3270,24 +3275,35 @@
 	return X86EMUL_CONTINUE;
 }
 
-int emulator_write_emulated(unsigned long addr,
+int __emulator_write_emulated(unsigned long addr,
 				   const void *val,
 				   unsigned int bytes,
-				   struct kvm_vcpu *vcpu)
+				   struct kvm_vcpu *vcpu,
+				   bool mmu_only)
 {
 	/* Crossing a page boundary? */
 	if (((addr + bytes - 1) ^ addr) & PAGE_MASK) {
 		int rc, now;
 
 		now = -addr & ~PAGE_MASK;
-		rc = emulator_write_emulated_onepage(addr, val, now, vcpu);
+		rc = emulator_write_emulated_onepage(addr, val, now, vcpu,
+						     mmu_only);
 		if (rc != X86EMUL_CONTINUE)
 			return rc;
 		addr += now;
 		val += now;
 		bytes -= now;
 	}
-	return emulator_write_emulated_onepage(addr, val, bytes, vcpu);
+	return emulator_write_emulated_onepage(addr, val, bytes, vcpu,
+					       mmu_only);
+}
+
+int emulator_write_emulated(unsigned long addr,
+				   const void *val,
+				   unsigned int bytes,
+				   struct kvm_vcpu *vcpu)
+{
+	return __emulator_write_emulated(addr, val, bytes, vcpu, false);
 }
 EXPORT_SYMBOL_GPL(emulator_write_emulated);
 
@@ -3351,6 +3367,8 @@
 	if (!exchanged)
 		return X86EMUL_CMPXCHG_FAILED;
 
+	return __emulator_write_emulated(addr, new, bytes, vcpu, true);
+
 emul_write:
 	printk_once(KERN_WARNING "kvm: emulating exchange as write\n");
 
@@ -4005,7 +4023,7 @@
 
 	kvm_x86_ops->patch_hypercall(vcpu, instruction);
 
-	return emulator_write_emulated(rip, instruction, 3, vcpu);
+	return __emulator_write_emulated(rip, instruction, 3, vcpu, false);
 }
 
 static u64 mk_cr_64(u64 curr_cr, u32 new_val)