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authorPaolo Bonzini <pbonzini@redhat.com>2015-02-12 17:04:47 +0100
committerSasha Levin <sasha.levin@oracle.com>2015-03-14 15:37:22 -0400
commitc8b6504b25d2894e7e3b4909bae15ebcd740120b (patch)
treeabbfb11b282b32c25704528809b2381b2ef4473a /arch
parent218c886394e239706714caec1fb5d7c47fcb54c8 (diff)
KVM: emulate: fix CMPXCHG8B on 32-bit hosts
commit 4ff6f8e61eb7f96d3ca535c6d240f863ccd6fb7d upstream. This has been broken for a long time: it broke first in 2.6.35, then was almost fixed in 2.6.36 but this one-liner slipped through the cracks. The bug shows up as an infinite loop in Windows 7 (and newer) boot on 32-bit hosts without EPT. Windows uses CMPXCHG8B to write to page tables, which causes a page fault if running without EPT; the emulator is then called from kvm_mmu_page_fault. The loop then happens if the higher 4 bytes are not 0; the common case for this is that the NX bit (bit 63) is 1. Fixes: 6550e1f165f384f3a46b60a1be9aba4bc3c2adad Fixes: 16518d5ada690643453eb0aef3cc7841d3623c2d Reported-by: Erik Rull <erik.rull@rdsoftware.de> Tested-by: Erik Rull <erik.rull@rdsoftware.de> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/emulate.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index c7327a7761ca..974e4d98ed29 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4829,7 +4829,8 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
if (rc != X86EMUL_CONTINUE)
goto done;
}
- ctxt->dst.orig_val = ctxt->dst.val;
+ /* Copy full 64-bit value for CMPXCHG8B. */
+ ctxt->dst.orig_val64 = ctxt->dst.val64;
special_insn: