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authorPaolo Bonzini <pbonzini@redhat.com>2015-02-12 17:04:47 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2015-02-23 22:28:48 +0100
commit4ff6f8e61eb7f96d3ca535c6d240f863ccd6fb7d (patch)
treebfd41b00d5b6ae5797edb03d8d0459832d049cd0 /arch/x86/kvm/emulate.c
parent21bc8dc5b729dbeecb43adff23b74b51321e1897 (diff)
downloadop-kernel-dev-4ff6f8e61eb7f96d3ca535c6d240f863ccd6fb7d.zip
op-kernel-dev-4ff6f8e61eb7f96d3ca535c6d240f863ccd6fb7d.tar.gz
KVM: emulate: fix CMPXCHG8B on 32-bit hosts
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 Cc: stable@vger.kernel.org # 2.6.35+ Reported-by: Erik Rull <erik.rull@rdsoftware.de> Tested-by: Erik Rull <erik.rull@rdsoftware.de> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/emulate.c')
-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 e0b794a..106c015 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4950,7 +4950,8 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
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:
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