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bh=/E1zRKy22hQflBQKNHHIXyCaNj0DFPnik7y+EzsA1xs=; b=jOPn0/bVXdG+ZgdZfoPdDKBCuVhEN0DKcCx3sluxI3RtWeqpmjKf9zTq8x1NDwm6PdLOkw nXPU+6pxTjLUmR3/fa5+y4TqrqTS3qcv+Dejqrx/LIWlJiWS2kOgeYS4AAPk2bXy59qavZ JArap5Qun8iYPhX3qfFXOIfmZBJEmbk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-512-gNGGSlDsNYuRPZ47etqv1A-1; Wed, 26 May 2021 12:56:58 -0400 X-MC-Unique: gNGGSlDsNYuRPZ47etqv1A-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5F14A100747C for ; Wed, 26 May 2021 16:56:57 +0000 (UTC) Received: from redhat.com (ovpn-115-19.ams2.redhat.com [10.36.115.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B04955D9D3; Wed, 26 May 2021 16:56:55 +0000 (UTC) Date: Wed, 26 May 2021 17:56:52 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Eduardo Habkost Subject: Re: [PATCH v6 13/19] i386: prefer system KVM_GET_SUPPORTED_HV_CPUID ioctl over vCPU's one Message-ID: References: <20210422161130.652779-1-vkuznets@redhat.com> <20210422161130.652779-14-vkuznets@redhat.com> <20210521214202.g222ullptiseaesq@habkost.net> <87h7is72rp.fsf@vitty.brq.redhat.com> <20210526164625.ci5xou7ikuiqkrpz@habkost.net> MIME-Version: 1.0 In-Reply-To: <20210526164625.ci5xou7ikuiqkrpz@habkost.net> User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.371, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Paolo Bonzini , Vitaly Kuznetsov , Marcelo Tosatti , qemu-devel@nongnu.org, Igor Mammedov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, May 26, 2021 at 12:46:25PM -0400, Eduardo Habkost wrote: > On Mon, May 24, 2021 at 02:08:26PM +0200, Vitaly Kuznetsov wrote: > [...] > > >> @@ -980,7 +989,7 @@ static struct kvm_cpuid2 *get_supported_hv_cpuid(CPUState *cs) > > >> * information early, just check for the capability and set the bit > > >> * manually. > > >> */ > > >> - if (kvm_check_extension(cs->kvm_state, > > >> + if (!do_sys_ioctl && kvm_check_extension(cs->kvm_state, > > >> KVM_CAP_HYPERV_ENLIGHTENED_VMCS) > 0) { > > > > > > Oh, this conditional replaces the comment I suggested in patch > > > 10/19. It makes it obvious that the hack can be deleted if we > > > remove support for the VCPU ioctl. > > > > > > So, when exactly will we be able to delete the VCPU ioctl code > > > and support only the system ioctl? > > > > When QEMU drops support for kernels < 5.11? Note, current RHEL8 already > > supports system version so we're talking about upstream kernels/Ubuntu > > LTS/... > > > > I remember there was a list of supported kernels for QEMU somewhere but > > don't seem to be able to find it quickly, could you maybe point me in > > the right direction? > > The KVM-specific kernel requirement is documented here: > https://qemu-project.gitlab.io/qemu/system/target-i386.html?highlight=kvm#os-requirements > > I took a while to find it. Maybe we should have a more visible > "runtime requirements" section in the docs, or it should be > moved to the supported build platforms section. > > We have a clear policy on supported build platforms > [https://qemu-project.gitlab.io/qemu/system/build-platforms.html], > but not a clear policy for KVM kernel dependencies. While it says "supported build platforms", that was implicitly assumed to also refer to "runtime platforms". We should just rename it to "supported-platforms.html" to make it more obvious. Thus, the minimum KVM kernel version we need follows the same rules. Look at whatever is the oldest kernel across the distros we target. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|