This is a note to let you know that I've just added the patch titled
KVM: emulate: fix CMPXCHG8B on 32-bit hosts
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-emulate-fix-cmpxchg8b-on-32-bit-hosts.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 4ff6f8e61eb7f96d3ca535c6d240f863ccd6fb7d Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <[email protected]>
Date: Thu, 12 Feb 2015 17:04:47 +0100
Subject: KVM: emulate: fix CMPXCHG8B on 32-bit hosts
From: Paolo Bonzini <[email protected]>
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 <[email protected]>
Tested-by: Erik Rull <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/x86/kvm/emulate.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4646,7 +4646,8 @@ int x86_emulate_insn(struct x86_emulate_
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:
Patches currently in stable-queue which might be from [email protected] are
queue-3.14/kvm-emulate-fix-cmpxchg8b-on-32-bit-hosts.patch
queue-3.14/kvm-mips-fix-trace-event-to-save-pc-directly.patch
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