From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45913) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1faKSn-0003lF-V9 for qemu-devel@nongnu.org; Tue, 03 Jul 2018 08:31:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1faKSh-0006VU-Ur for qemu-devel@nongnu.org; Tue, 03 Jul 2018 08:31:21 -0400 References: <1529500053-21704-1-git-send-email-eric.auger@redhat.com> <1529500053-21704-6-git-send-email-eric.auger@redhat.com> <20180703115507.nqmyo7c5q5lrevgt@kamzik.brq.redhat.com> From: Auger Eric Message-ID: <31c24e33-8fe8-a3c0-0430-d2f503f10932@redhat.com> Date: Tue, 3 Jul 2018 14:31:02 +0200 MIME-Version: 1.0 In-Reply-To: <20180703115507.nqmyo7c5q5lrevgt@kamzik.brq.redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC 5/6] hw/arm/virt: support kvm_type property List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Andrew Jones Cc: eric.auger.pro@gmail.com, qemu-devel@nongnu.org, qemu-arm@nongnu.org, peter.maydell@linaro.org, wei@redhat.com, suzuki.poulose@arm.com, dgilbert@redhat.com, agraf@suse.de, david@gibson.dropbear.id.au Hi Drew, On 07/03/2018 01:55 PM, Andrew Jones wrote: > On Wed, Jun 20, 2018 at 03:07:32PM +0200, Eric Auger wrote: >> The kvm-type property currently is used to pass >> a user parameter to KVM_CREATE_VM. This matches >> the way KVM/ARM expects to pass the max_vm_phys_shift >> parameter. >> >> This patch adds the support or the kvm-type property in >> machvirt and also implements the machine class kvm_type() >> callback so that it either returns the kvm-type value >> provided by the user or returns the max_vm_phys_shift >> exposed by KVM. >> >> for instance, the usespace can use the following option to >> instantiate a 42b IPA guest: -machine kvm-type=42 > > 'kvm-type' is a very generic name. It looks like you're creating a KVM > VM of type 42 (which I assume is the ultimate KVM VM that answers the > meaning to Life, the Universe, and Everything), but it's not obvious > how it relates to physical address bits. Why not call this property > something like 'min_vm_phys_shift'? Notice the 'min' in the name, > because this is where the user is stating what the minimum number of > physical address bits required for the VM is. IIUC, if KVM supports > more, then it shouldn't be a problem. Well I agree with you that using kvm-type=42 is not very nice. On the other hand the current kernel API to pass the VM GPA address size is though the KVM_CREATE_VM kvm_type argument. in accel/kvm/kvm-all.c there is all the infrastructure to fetch the generic machine kvm-type machine option and decode it into type, which is passed to KVM_CREATE_VM. " kvm_type = qemu_opt_get(qemu_get_machine_opts(), "kvm-type"); if (mc->kvm_type) { type = mc->kvm_type(ms, kvm_type); } else if (kvm_type) { ret = -EINVAL; fprintf(stderr, "Invalid argument kvm-type=%s\n", kvm_type); goto err; } do { ret = kvm_ioctl(s, KVM_CREATE_VM, type); } while (ret == -EINTR); " This infrastructure already is used in hw/ppc/spapr.c Whould it be better if we would pass something like kvm-type=48bGPA? Otherwise I can decode another virt machine option (min_vm_phys_shift) in kvm_type callback. Thanks Eric > > Thanks, > drew >