From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] target-i386: add feature flags for CPUID[EAX=0xd,ECX=1] Date: Wed, 26 Nov 2014 10:20:12 +0100 Message-ID: <54759B4C.5060601@redhat.com> References: <1416936942-32516-1-git-send-email-pbonzini@redhat.com> <20141125184517.GP3137@thinpad.lan.raisama.net> <5474E05E.7090509@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org To: Eduardo Habkost Return-path: Received: from mail-wi0-f170.google.com ([209.85.212.170]:51788 "EHLO mail-wi0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750848AbaKZJUR (ORCPT ); Wed, 26 Nov 2014 04:20:17 -0500 Received: by mail-wi0-f170.google.com with SMTP id bs8so14455016wib.1 for ; Wed, 26 Nov 2014 01:20:15 -0800 (PST) In-Reply-To: <5474E05E.7090509@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 25/11/2014 21:02, Paolo Bonzini wrote: > > > +static const char *cpuid_xsave_feature_name[] = { > > > + "xsaveopt", "xsavec", "xgetbv1", "xsaves", > > > > None of the above features introduce any new state that might need to be > > migrated, or will require other changes in QEMU to work, right? > > > > It looks like they don't introduce any extra state, but if they do, they > > need to be added to unmigratable_flags until migration support is > > implemented. > > > > If they require other QEMU changes, it would be nice if KVM reported > > them using KVM_CHECK_EXTENSION instead of GET_SUPPORTED_CPUID, so it > > wouldn't break "-cpu host". > > No, they don't. Actually, xsaves does but I don't think KVM_CHECK_EXTENSION is right. It's just another MSR, and we haven't used KVM_CHECK_EXTENSION for new MSRs and new XSAVE areas (last example: avx512). Since no hardware really exists for it, and KVM does not support it anyway, I think it's simplest to leave xsaves out for now. Is this right? Paolo