Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752232AbbGMPNI (ORCPT ); Mon, 13 Jul 2015 11:13:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33519 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751098AbbGMPNF (ORCPT ); Mon, 13 Jul 2015 11:13:05 -0400 Subject: Re: [PATCH v3 01/10] KVM: MMU: fix decoding cache type from MTRR To: Xiao Guangrong , Alex Williamson 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> <55A2B8F7.1050805@linux.intel.com> <55A36976.6090807@redhat.com> <55A3CEF2.2030200@linux.intel.com> Cc: gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org From: Paolo Bonzini Message-ID: <55A3D57C.4050100@redhat.com> Date: Mon, 13 Jul 2015 17:13:00 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.0.1 MIME-Version: 1.0 In-Reply-To: <55A3CEF2.2030200@linux.intel.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: 1554 Lines: 48 On 13/07/2015 16:45, Xiao Guangrong wrote: >> + /* MTRR is completely disabled, use UC for all of physical >> memory. */ >> + if (!(mtrr_state->enabled & 0x2)) >> + return MTRR_TYPE_UNCACHABLE; >> >> actually disappears in commit fa61213746a7 (KVM: MTRR: simplify >> kvm_mtrr_get_guest_memory_type, 2015-06-15). > > :( > > Based on the SDM, UC is applied to all memory rather than default-type > if MTRR is disabled. There are two issues I think. One is that I cannot find in the current code that "UC is applied to all memory rather than default-type if MTRR is disabled". mtrr_default_type unconditionally looks at mtrr_state->deftype. > However, fast boot came back if "return 0xFF" here. So fast boot expects > that the memory type is WB. Yes. >> >> static u8 mtrr_default_type(struct kvm_mtrr *mtrr_state) >> { >> if (mtrr_is_enabled(mtrr_state)) >> return mtrr_state->deftype & >> IA32_MTRR_DEF_TYPE_TYPE_MASK; >> else >> return MTRR_TYPE_UNCACHABLE; >> } >> >> ? Then it's easy to add a quirk that makes the default WRITEBACK until >> MTRRs are enabled. > > It is the wrong configure in OVMF... shall we need to adjust KVM to satisfy > OVMF? That's what quirks are for... The firmware should still be fixed of course. Paolo -- 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/