Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757365AbbFPJ0y (ORCPT ); Tue, 16 Jun 2015 05:26:54 -0400 Received: from mail.kernel.org ([198.145.29.136]:55133 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932504AbbFPInE (ORCPT ); Tue, 16 Jun 2015 04:43:04 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Paolo Bonzini , Zefan Li Subject: [PATCH 3.4 053/172] KVM: emulate: fix CMPXCHG8B on 32-bit hosts Date: Tue, 16 Jun 2015 16:35:07 +0800 Message-Id: <1434443826-4929-53-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1434443587-4599-1-git-send-email-lizf@kernel.org> References: <1434443587-4599-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1756 Lines: 51 From: Paolo Bonzini 3.4.108-rc1 review patch. If anyone has any objections, please let me know. ------------------ 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 Tested-by: Erik Rull Signed-off-by: Paolo Bonzini Signed-off-by: Zefan Li --- arch/x86/kvm/emulate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 91e8680..db08e66 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4246,7 +4246,8 @@ 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: -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/