From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:36706) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TqUy0-00065X-8r for qemu-devel@nongnu.org; Wed, 02 Jan 2013 15:31:14 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TqUxy-0003YS-TQ for qemu-devel@nongnu.org; Wed, 02 Jan 2013 15:31:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35548) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TqUxy-0003Y2-M0 for qemu-devel@nongnu.org; Wed, 02 Jan 2013 15:31:10 -0500 Date: Wed, 2 Jan 2013 21:30:20 +0100 From: Igor Mammedov Message-ID: <20130102213020.6310f028@thinkpad.mammed.net> In-Reply-To: <20130102152910.GG18372@otherpad.lan.raisama.net> References: <1356719854-16401-1-git-send-email-ehabkost@redhat.com> <1356719854-16401-3-git-send-email-ehabkost@redhat.com> <20130102155245.3e709464@nial.usersys.redhat.com> <20130102152910.GG18372@otherpad.lan.raisama.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 2/2] target-i386: kvm: enable all supported KVM features for -cpu host List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: kvm@vger.kernel.org, Gleb Natapov , "Michael S. Tsirkin" , Marcelo Tosatti , qemu-devel@nongnu.org, Andreas =?UTF-8?B?RsOkcmJlcg==?= On Wed, 2 Jan 2013 13:29:10 -0200 Eduardo Habkost wrote: > On Wed, Jan 02, 2013 at 03:52:45PM +0100, Igor Mammedov wrote: > > On Fri, 28 Dec 2012 16:37:34 -0200 > > Eduardo Habkost wrote: > > > > > When using -cpu host, we don't need to use the kvm_default_features > > > variable, as the user is explicitly asking QEMU to enable all feature > > > supported by the host. > > > > > > This changes the kvm_cpu_fill_host() code to use GET_SUPPORTED_CPUID to > > > initialize the kvm_features field, so we get all host KVM features > > > enabled. > > > > 1_2 and 1_3 compat machines diff on pv_eoi flag, with this patch 1_2 might > > have it set. > > Is it ok from compat machines pov? > > -cpu host is completely dependent on host hardware and kernel version, > there are no compatibility expectations. It's still kind of unpleasant surprise if on the same host "qemu-1.3 -cpu host -machine pc-1.2" and "qemu-1.3+ -cpu host -machine pc-1.2" would give different pv_eoi feature default, where pv-eoi should be available after -machine pc-1.2 by default. > > > > > > > > > This will also allow use to properly check/enforce KVM features inside > > > kvm_check_features_against_host() later. For example, we will be able to > > > make this: > > > > > > $ qemu-system-x86_64 -cpu ...,+kvm_pv_eoi,enforce > > > > > > refuse to start if kvm_pv_eoi is not supported by the host (after we fix > > > kvm_check_features_against_host() to check KVM flags as well). > > It would be nice to have kvm_check_features_against_host() patch in this > > series to verify that this patch and previous patch works as expected. > > The kvm_check_features_against_host() change would be a user-visible > behavior change, and I wanted to keep the changes minimal by now. (the > main reason I submitted this earlier is to make it easier to clean up > the init code for CPU subclasses) > > I was planning to introduce those behavior changes only after > introducing the feature-word array, so the kvm_check_features_against_host() > code can become simpler and easier to review (instead of adding 4 > additional items to the messy struct model_features_t array). But if you > think we can introduce those changes now, I will be happy to send a > series that changes that code as well. It would be better if it and simplifying kvm_check_features_against_host() were in here together. > > > > > > > > > Signed-off-by: Eduardo Habkost > > > --- > > > target-i386/cpu.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > > > index 6e2d32d..76f19f0 100644 > > > --- a/target-i386/cpu.c > > > +++ b/target-i386/cpu.c > > > @@ -900,6 +900,8 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def) > > > /* Other KVM-specific feature fields: */ > > > x86_cpu_def->svm_features = > > > kvm_arch_get_supported_cpuid(s, 0x8000000A, 0, R_EDX); > > > + x86_cpu_def->kvm_features = > > > + kvm_arch_get_supported_cpuid(s, KVM_CPUID_FEATURES, 0, > > > R_EAX); > > > #endif /* CONFIG_KVM */ > > > } > > > > -- > Eduardo > -- Regards, Igor