From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eduardo Habkost Subject: Re: [PATCH] target-i386: fix losing XCR0 processor state component bits Date: Wed, 28 Sep 2016 11:57:37 -0300 Message-ID: <20160928145737.GJ3877@thinpad.lan.raisama.net> References: <1475040669-29085-1-git-send-email-wanpeng.li@hotmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Wanpeng Li , kvm@vger.kernel.org, qemu-devel@nongnu.org, Wanpeng Li , Richard Henderson , "Michael S. Tsirkin" To: Paolo Bonzini Return-path: Received: from mx1.redhat.com ([209.132.183.28]:53408 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932777AbcI1O5k (ORCPT ); Wed, 28 Sep 2016 10:57:40 -0400 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Sep 28, 2016 at 09:54:27AM +0200, Paolo Bonzini wrote: > > > On 28/09/2016 07:31, Wanpeng Li wrote: > > From: Wanpeng Li > > > > Commit 96193c22a "target-i386: Move xsave component mask to features array" > > leverages features array to handle XCR0 processor state component bits, > > however, it introduces a regression: > > > > warning: host doesn't support requested feature: CPUID.0DH:EAX [bit 0] > > warning: host doesn't support requested feature: CPUID.0DH:EAX [bit 1] > > warning: host doesn't support requested feature: CPUID.0DH:EAX [bit 2] > > > > My desktop doesn't have enough advance features, so just X87,SSE,AVX > > warnings are splat when I boot a guest. Oops. I assume this is reproducible only using "-cpu host"? > > > > The get migratable flags logic in x86_cpu_filter_features() path will > > filter out the feature flags which are unsupported and unmigratable. > > However, the bits of XCR0 processor state component featureword don't > > have feat_names, and some features like SSE/AVX etc have feat_names in > > CPUID.01H:EDX, CPUID.01H:ECX, so they are treated as unsupported. > > > > This patch fix it by don't filter out XCR0 processor state components > > bits though they don't have feat_names just as before commit 96193c22ab3. > > > > Cc: Paolo Bonzini > > Cc: Richard Henderson > > Cc: Eduardo Habkost > > Cc: Michael S. Tsirkin > > Signed-off-by: Wanpeng Li > > --- > > target-i386/cpu.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > > index ad09246..9d24eff 100644 > > --- a/target-i386/cpu.c > > +++ b/target-i386/cpu.c > > @@ -2156,6 +2156,10 @@ static uint32_t x86_cpu_get_supported_feature_word(FeatureWord w, > > r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid_eax, > > wi->cpuid_ecx, > > wi->cpuid_reg); > > + if ((w == FEAT_XSAVE_COMP_LO) || > > + (w == FEAT_XSAVE_COMP_HI)) { > > + return r; > > + } > > } else if (tcg_enabled()) { > > r = wi->tcg_features; > > } else { > > > > I think the right place to add the test is x86_cpu_get_migratable_flags. This can be fixed by adding actual property names to the FEAT_XSAVE_COMP_* bits. This way we will be able to report meaningful names to management in case GET_SUPPORTED_CPUID says a given xsave component is not supported yet, and will ensure we correctly treat still-unknown xsave components as unmigratable. -- Eduardo From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42048) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bpGIr-0007eB-UY for qemu-devel@nongnu.org; Wed, 28 Sep 2016 10:57:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bpGIn-0006LM-LM for qemu-devel@nongnu.org; Wed, 28 Sep 2016 10:57:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57590) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bpGIn-0006L4-BU for qemu-devel@nongnu.org; Wed, 28 Sep 2016 10:57:41 -0400 Date: Wed, 28 Sep 2016 11:57:37 -0300 From: Eduardo Habkost Message-ID: <20160928145737.GJ3877@thinpad.lan.raisama.net> References: <1475040669-29085-1-git-send-email-wanpeng.li@hotmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH] target-i386: fix losing XCR0 processor state component bits List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Wanpeng Li , kvm@vger.kernel.org, qemu-devel@nongnu.org, Wanpeng Li , Richard Henderson , "Michael S. Tsirkin" On Wed, Sep 28, 2016 at 09:54:27AM +0200, Paolo Bonzini wrote: > > > On 28/09/2016 07:31, Wanpeng Li wrote: > > From: Wanpeng Li > > > > Commit 96193c22a "target-i386: Move xsave component mask to features array" > > leverages features array to handle XCR0 processor state component bits, > > however, it introduces a regression: > > > > warning: host doesn't support requested feature: CPUID.0DH:EAX [bit 0] > > warning: host doesn't support requested feature: CPUID.0DH:EAX [bit 1] > > warning: host doesn't support requested feature: CPUID.0DH:EAX [bit 2] > > > > My desktop doesn't have enough advance features, so just X87,SSE,AVX > > warnings are splat when I boot a guest. Oops. I assume this is reproducible only using "-cpu host"? > > > > The get migratable flags logic in x86_cpu_filter_features() path will > > filter out the feature flags which are unsupported and unmigratable. > > However, the bits of XCR0 processor state component featureword don't > > have feat_names, and some features like SSE/AVX etc have feat_names in > > CPUID.01H:EDX, CPUID.01H:ECX, so they are treated as unsupported. > > > > This patch fix it by don't filter out XCR0 processor state components > > bits though they don't have feat_names just as before commit 96193c22ab3. > > > > Cc: Paolo Bonzini > > Cc: Richard Henderson > > Cc: Eduardo Habkost > > Cc: Michael S. Tsirkin > > Signed-off-by: Wanpeng Li > > --- > > target-i386/cpu.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > > index ad09246..9d24eff 100644 > > --- a/target-i386/cpu.c > > +++ b/target-i386/cpu.c > > @@ -2156,6 +2156,10 @@ static uint32_t x86_cpu_get_supported_feature_word(FeatureWord w, > > r = kvm_arch_get_supported_cpuid(kvm_state, wi->cpuid_eax, > > wi->cpuid_ecx, > > wi->cpuid_reg); > > + if ((w == FEAT_XSAVE_COMP_LO) || > > + (w == FEAT_XSAVE_COMP_HI)) { > > + return r; > > + } > > } else if (tcg_enabled()) { > > r = wi->tcg_features; > > } else { > > > > I think the right place to add the test is x86_cpu_get_migratable_flags. This can be fixed by adding actual property names to the FEAT_XSAVE_COMP_* bits. This way we will be able to report meaningful names to management in case GET_SUPPORTED_CPUID says a given xsave component is not supported yet, and will ensure we correctly treat still-unknown xsave components as unmigratable. -- Eduardo