Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753591AbbGNV3R (ORCPT ); Tue, 14 Jul 2015 17:29:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58757 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751708AbbGNV3P (ORCPT ); Tue, 14 Jul 2015 17:29:15 -0400 Message-ID: <55A57F27.6090705@redhat.com> Date: Tue, 14 Jul 2015 23:29:11 +0200 From: Laszlo Ersek User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Paolo Bonzini CC: Xiao Guangrong , Alex Williamson , gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, edk2-devel list , "Jordan Justen (Intel address)" Subject: Re: MTRR setup in OVMF [was: PATCH v3 01/10 KVM: MMU: fix decoding cache type from MTRR] References: <1431499348-25188-1-git-send-email-guangrong.xiao@linux.intel.com> <1436722432.1391.347.camel@redhat.com> <55A2B8F7.1050805@linux.intel.com> <55A36976.6090807@redhat.com> <55A3CEF2.2030200@linux.intel.com> <55A3D57C.4050100@redhat.com> <55A3D616.8010209@linux.intel.com> <55A57B54.2040305@redhat.com> <922266674.41385307.1436908536320.JavaMail.zimbra@redhat.com> In-Reply-To: <922266674.41385307.1436908536320.JavaMail.zimbra@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1791 Lines: 41 On 07/14/15 23:15, Paolo Bonzini wrote: >> The long delay that Alex reported (for the case when all guest memory >> was set to UC up-front) is due to the fact that the SEC phase of OVMF >> decompresses an approximately 1712 KB sized, LZMA-compressed blob, to >> approx. 896 KB worth of PEI drivers and 8192 KB worth of DXE and UEFI >> drivers -- and this decompression is extremely memory-intensive. >> >> (When Jordan implemented that reset vector first, we saw similar >> performance degradation on AMD hosts (albeit not due to MTRR but due to >> page attributes). See >> . I'm only mentioning >> it here because it makes me appreciate the current problem report.) >> >> Anyway, the reset vector's page table building is implemented in >> "OvmfPkg/ResetVector/Ia32/PageTables64.asm". The decompression in SEC >> can be found in "OvmfPkg/Sec/SecMain.c", function DecompressMemFvs(). > > Perhaps the OVMF reset vector should initialize the MTRRs for the BSP? That's an idea, yes, if someone feels sufficiently drawn to writing assembly. Complications: - the reset vector is specific to OvmfPkg only in the OvmfPkgX64.dsc build - it needs to be determined what memory to cover. > I think SEC doesn't do any MMIO, so it should be enough to enable MTRRs > and set the default type to writeback. Seems safe to me, off the top of my head (and testing could confirm / disprove quickly). > In any case we're going to have to quirk it, because of the broken > guests in the wild. Thanks. Laszlo -- 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/