From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Walls Subject: Re: [PATCH] KVM: Don't allow lmsw to clear cr0.pe Date: Wed, 12 May 2010 12:18:14 -0400 Message-ID: <1273681094.3991.13.camel@localhost> References: <1273613324-31910-1-git-send-email-avi@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from proofpoint-cluster.metrocast.net ([65.175.128.136]:12905 "EHLO proofpoint-cluster.metrocast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754550Ab0ELQTy (ORCPT ); Wed, 12 May 2010 12:19:54 -0400 In-Reply-To: <1273613324-31910-1-git-send-email-avi@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, 2010-05-12 at 00:28 +0300, Avi Kivity wrote: > The current lmsw implementation allows the guest to clear cr0.pe, contrary > to the manual, which breaks EMM386.EXE. > > Fix by ORing the old cr0.pe with lmsw's operand. > > Signed-off-by: Avi Kivity > --- > arch/x86/kvm/x86.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index cd8a606..a40170c 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -462,7 +462,7 @@ EXPORT_SYMBOL_GPL(kvm_set_cr0); > > void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw) > { > - kvm_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~0x0ful) | (msw & 0x0f)); > + kvm_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~0x0eul) | (msw & 0x0f)); > } > EXPORT_SYMBOL_GPL(kvm_lmsw); > This patch works for me. The old programs I have that use the DOS/4GW extender (http://www.tenberry.com/) runtime no longer hanging the MS-DOS 6.22 guest when EMM386.EXE is loaded and the "set_cr0: #GP..." message is no longer filling the logs. :) Now I have a different problem. dmesg is filling with "skip_emulated_instruction: NOP" messages. As I investigate further, I unfortunately found that RHEL 5 has a somewhat dated kvm package: ftp://ftp.redhat.com/redhat/linux/enterprise/5Client/en/os/SRPMS/kvm-83-164.el5.src.rpm that looks to be based on a KVM snapshot from around May of last year. It appears to missing some recent patches in regard to skip_emulated_instruction(). :( Oh well. I'll try qemu without KVM hardware acceleration. Thanks for the fast response on the LMSW patch. Regards, Andy