From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48650) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dsjHQ-00069c-5n for qemu-devel@nongnu.org; Fri, 15 Sep 2017 01:35:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dsjHM-0008Uz-7S for qemu-devel@nongnu.org; Fri, 15 Sep 2017 01:35:08 -0400 References: <150541711102.1616.2690784964841960181.stgit@bahia.lan> <150541713284.1616.15291547955159941369.stgit@bahia.lan> From: Thomas Huth Message-ID: Date: Fri, 15 Sep 2017 07:34:59 +0200 MIME-Version: 1.0 In-Reply-To: <150541713284.1616.15291547955159941369.stgit@bahia.lan> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 2/3] kvm: check KVM_CAP_NR_VCPUS with kvm_vm_check_extension() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz , qemu-devel@nongnu.org Cc: qemu-ppc@nongnu.org, David Gibson , Sam Bobroff , Paolo Bonzini On 14.09.2017 21:25, Greg Kurz wrote: > On a modern server-class ppc host with the following CPU topology: > > Architecture: ppc64le > Byte Order: Little Endian > CPU(s): 32 > On-line CPU(s) list: 0,8,16,24 > Off-line CPU(s) list: 1-7,9-15,17-23,25-31 > Thread(s) per core: 1 > > If both KVM PR and KVM HV loaded and we pass: > > -machine pseries,accel=kvm,kvm-type=PR -smp 8 > > We expect QEMU to warn that this exceeds the number of online CPUs: > > Warning: Number of SMP cpus requested (8) exceeds the recommended > cpus supported by KVM (4) > Warning: Number of hotpluggable cpus requested (8) exceeds the > recommended cpus supported by KVM (4) > > but nothing is printed... > > This happens because on ppc the KVM_CAP_NR_VCPUS capability is VM > specific ndreally depends on the KVM type, but we currently use it > as a global capability. And KVM returns a fallback value based on > KVM HV being present. Maybe KVM on POWER shouldn't presume anything > as long as it doesn't have a VM, but in all cases, we should call > KVM_CREATE_VM first and use KVM_CAP_NR_VCPUS as a VM capability. > > This patch hence changes kvm_recommended_vcpus() accordingly and > moves the sanity checking of smp_cpus after the VM creation. > > It is okay for the other archs that also implement KVM_CAP_NR_VCPUS, > ie, mips, s390, x86 and arm, because they don't depend on the VM > being created or not. > > Signed-off-by: Greg Kurz > --- > accel/kvm/kvm-all.c | 45 +++++++++++++++++++++++---------------------- > 1 file changed, 23 insertions(+), 22 deletions(-) > > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c > index 323c567cfb68..d10534de2da1 100644 > --- a/accel/kvm/kvm-all.c > +++ b/accel/kvm/kvm-all.c > @@ -1533,7 +1533,7 @@ static void kvm_irqchip_create(MachineState *machine, KVMState *s) > */ > static int kvm_recommended_vcpus(KVMState *s) > { > - int ret = kvm_check_extension(s, KVM_CAP_NR_VCPUS); > + int ret = kvm_vm_check_extension(s, KVM_CAP_NR_VCPUS); > return (ret) ? ret : 4; > } > > @@ -1623,27 +1623,6 @@ static int kvm_init(MachineState *ms) > s->nr_slots = 32; > } > > - /* check the vcpu limits */ > - soft_vcpus_limit = kvm_recommended_vcpus(s); > - hard_vcpus_limit = kvm_max_vcpus(s); > - > - while (nc->name) { > - if (nc->num > soft_vcpus_limit) { > - fprintf(stderr, > - "Warning: Number of %s cpus requested (%d) exceeds " > - "the recommended cpus supported by KVM (%d)\n", > - nc->name, nc->num, soft_vcpus_limit); > - > - if (nc->num > hard_vcpus_limit) { > - fprintf(stderr, "Number of %s cpus requested (%d) exceeds " > - "the maximum cpus supported by KVM (%d)\n", > - nc->name, nc->num, hard_vcpus_limit); > - exit(1); > - } > - } > - nc++; > - } > - > kvm_type = qemu_opt_get(qemu_get_machine_opts(), "kvm-type"); > if (mc->kvm_type) { > type = mc->kvm_type(kvm_type); > @@ -1678,6 +1657,28 @@ static int kvm_init(MachineState *ms) > } > > s->vmfd = ret; > + > + /* check the vcpu limits */ > + soft_vcpus_limit = kvm_recommended_vcpus(s); > + hard_vcpus_limit = kvm_max_vcpus(s); > + > + while (nc->name) { > + if (nc->num > soft_vcpus_limit) { > + fprintf(stderr, > + "Warning: Number of %s cpus requested (%d) exceeds " > + "the recommended cpus supported by KVM (%d)\n", > + nc->name, nc->num, soft_vcpus_limit); > + > + if (nc->num > hard_vcpus_limit) { > + fprintf(stderr, "Number of %s cpus requested (%d) exceeds " > + "the maximum cpus supported by KVM (%d)\n", > + nc->name, nc->num, hard_vcpus_limit); > + exit(1); > + } > + } > + nc++; > + } > + > missing_cap = kvm_check_extension_list(s, kvm_required_capabilites); > if (!missing_cap) { > missing_cap = > Reviewed-by: Thomas Huth