Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751390AbbGLTMT (ORCPT ); Sun, 12 Jul 2015 15:12:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49469 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751148AbbGLTMS (ORCPT ); Sun, 12 Jul 2015 15:12:18 -0400 From: Bandan Das To: Alex Williamson Cc: Xiao Guangrong , pbonzini@redhat.com, gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 01/10] KVM: MMU: fix decoding cache type from MTRR 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> Date: Sun, 12 Jul 2015 15:12:16 -0400 In-Reply-To: <1436722432.1391.347.camel@redhat.com> (Alex Williamson's message of "Sun, 12 Jul 2015 11:33:52 -0600") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3126 Lines: 86 Alex Williamson writes: > 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; Setting this to UC if MTRR is disabled is too restrictive maybe.. Bandan >> /* 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 kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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/