From: Wei Yongjun <yjwei@cn.fujitsu.com>
Date: Thu, 15 Jul 2010 00:51:58 +0000 (+0800)
Subject: KVM: x86 emulator: fix xchg instruction emulation
X-Git-Tag: firefly_0821_release~9833^2~1315^2~8
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c19b8bd60e19308d5583ef200ddcc782d85d9543;p=firefly-linux-kernel-4.4.55.git

KVM: x86 emulator: fix xchg instruction emulation

If the destination is a memory operand and the memory cannot
map to a valid page, the xchg instruction emulation and locked
instruction will not work on io regions and stuck in endless
loop. We should emulate exchange as write to fix it.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Acked-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 689c2c3182ab..97aab036dabf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3562,6 +3562,10 @@ static int emulator_cmpxchg_emulated(unsigned long addr,
 		goto emul_write;
 
 	page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);
+	if (is_error_page(page)) {
+		kvm_release_page_clean(page);
+		goto emul_write;
+	}
 
 	kaddr = kmap_atomic(page, KM_USER0);
 	kaddr += offset_in_page(gpa);