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| author | Paolo Bonzini <pbonzini@redhat.com> | 2015-02-12 17:04:47 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-03-18 14:10:59 +0100 |
| commit | d1feb25231a0653a395ed17baefc29aa42b43c9e (patch) | |
| tree | a02b18dc3098cebd6b9a6164ee9b2126c6cd9488 /arch | |
| parent | b0539dd5ecdcb164afc72aafd102db8626e42e49 (diff) | |
| download | lwn-d1feb25231a0653a395ed17baefc29aa42b43c9e.tar.gz lwn-d1feb25231a0653a395ed17baefc29aa42b43c9e.zip | |
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/emulate.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index de12c1d379f1..b24c2d84dc20 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4863,7 +4863,8 @@ 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: |