From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH v3 01/10] KVM: MMU: fix decoding cache type from MTRR Date: Mon, 13 Jul 2015 02:59:03 +0800 Message-ID: <55A2B8F7.1050805@linux.intel.com> References: <1431499348-25188-1-git-send-email-guangrong.xiao@linux.intel.com> <1431499348-25188-2-git-send-email-guangrong.xiao@linux.intel.com> <1436722432.1391.347.camel@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: pbonzini@redhat.com, gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Alex Williamson Return-path: Received: from mga11.intel.com ([192.55.52.93]:3721 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751183AbbGLTEC (ORCPT ); Sun, 12 Jul 2015 15:04:02 -0400 In-Reply-To: <1436722432.1391.347.camel@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 07/13/2015 01:33 AM, Alex Williamson wrote: > On Wed, 2015-05-13 at 14:42 +0800, Xiao Guangrong wrote: >> There are some bugs in current get_mtrr_type(); >> 1: bit 1 of mtrr_state->enabled is corresponding bit 11 of >> IA32_MTRR_DEF_TYPE MSR which completely control MTRR's enablement >> that means other bits are ignored if it is cleared >> >> 2: the fixed MTRR ranges are controlled by bit 0 of >> mtrr_state->enabled (bit 10 of IA32_MTRR_DEF_TYPE) >> >> 3: if MTRR is disabled, UC is applied to all of physical memory rather >> than mtrr_state->def_type >> >> Signed-off-by: Xiao Guangrong >> --- >> arch/x86/kvm/mmu.c | 14 ++++++-------- >> 1 file changed, 6 insertions(+), 8 deletions(-) > > > I'm seeing a significant regression in boot performance on Intel > hardware with assigned devices that bisects back to this patch. There's > a long delay with Seabios between the version splash and execution of > option ROMs, and a _very_ long delay with OVMF before the display is > initialized. The delay is long enough that users are reporting their > previously working VM is hung with 100% CPU usage on v4.2-rc1. Thanks, > Alex, thanks for your report. I will try to reproduce and fix it asap.