Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751339AbbGLRd4 (ORCPT ); Sun, 12 Jul 2015 13:33:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49351 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750954AbbGLRdy (ORCPT ); Sun, 12 Jul 2015 13:33:54 -0400 Message-ID: <1436722432.1391.347.camel@redhat.com> Subject: Re: [PATCH v3 01/10] KVM: MMU: fix decoding cache type from MTRR From: Alex Williamson To: Xiao Guangrong Cc: pbonzini@redhat.com, gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Date: Sun, 12 Jul 2015 11:33:52 -0600 In-Reply-To: <1431499348-25188-2-git-send-email-guangrong.xiao@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> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2727 Lines: 76 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 > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index b78e83f..d00cebd 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -2393,19 +2393,20 @@ EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page); > static int get_mtrr_type(struct mtrr_state_type *mtrr_state, > u64 start, u64 end) > { > - int i; > u64 base, mask; > u8 prev_match, curr_match; > - int num_var_ranges = KVM_NR_VAR_MTRR; > + int i, num_var_ranges = KVM_NR_VAR_MTRR; > > - if (!mtrr_state->enabled) > - return 0xFF; > + /* MTRR is completely disabled, use UC for all of physical memory. */ > + if (!(mtrr_state->enabled & 0x2)) > + return MTRR_TYPE_UNCACHABLE; > > /* Make end inclusive end, instead of exclusive */ > end--; > > /* Look in fixed ranges. Just return the type as per start */ > - if (mtrr_state->have_fixed && (start < 0x100000)) { > + if (mtrr_state->have_fixed && (mtrr_state->enabled & 0x1) && > + (start < 0x100000)) { > int idx; > > if (start < 0x80000) { > @@ -2428,9 +2429,6 @@ static int get_mtrr_type(struct mtrr_state_type *mtrr_state, > * Look of multiple ranges matching this address and pick type > * as per MTRR precedence > */ > - if (!(mtrr_state->enabled & 2)) > - return mtrr_state->def_type; > - > prev_match = 0xFF; > for (i = 0; i < num_var_ranges; ++i) { > unsigned short start_state, end_state; -- 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/