[{"id":1768927,"web_url":"http://patchwork.ozlabs.org/comment/1768927/","msgid":"<20170915010021.GC5250@umbus.fritz.box>","list_archive_url":null,"date":"2017-09-15T01:00:21","subject":"Re: [Qemu-devel] [PATCH 2/3] kvm: check KVM_CAP_NR_VCPUS with\n\tkvm_vm_check_extension()","submitter":{"id":47,"url":"http://patchwork.ozlabs.org/api/people/47/","name":"David Gibson","email":"david@gibson.dropbear.id.au"},"content":"On Thu, Sep 14, 2017 at 09:25:32PM +0200, Greg Kurz wrote:\n1;4803;0c> On a modern server-class ppc host with the following CPU topology:\n> \n> Architecture: ppc64le\n> Byte Order: Little Endian\n> CPU(s): 32\n> On-line CPU(s) list: 0,8,16,24\n> Off-line CPU(s) list: 1-7,9-15,17-23,25-31\n> Thread(s) per core: 1\n> \n> If both KVM PR and KVM HV loaded and we pass:\n> \n> -machine pseries,accel=kvm,kvm-type=PR -smp 8\n> \n> We expect QEMU to warn that this exceeds the number of online CPUs:\n> \n> Warning: Number of SMP cpus requested (8) exceeds the recommended\n> cpus supported by KVM (4)\n> Warning: Number of hotpluggable cpus requested (8) exceeds the\n> recommended cpus supported by KVM (4)\n> \n> but nothing is printed...\n> \n> This happens because on ppc the KVM_CAP_NR_VCPUS capability is VM\n> specific ndreally depends on the KVM type, but we currently use it\n> as a global capability. And KVM returns a fallback value based on\n> KVM HV being present. Maybe KVM on POWER shouldn't presume anything\n> as long as it doesn't have a VM, but in all cases, we should call\n> KVM_CREATE_VM first and use KVM_CAP_NR_VCPUS as a VM capability.\n> \n> This patch hence changes kvm_recommended_vcpus() accordingly and\n> moves the sanity checking of smp_cpus after the VM creation.\n> \n> It is okay for the other archs that also implement KVM_CAP_NR_VCPUS,\n> ie, mips, s390, x86 and arm, because they don't depend on the VM\n> being created or not.\n> \n> Signed-off-by: Greg Kurz \n\nReviewed-by: David Gibson \n\n> ---\n> accel/kvm/kvm-all.c | 45 +++++++++++++++++++++++----------------------\n> 1 file changed, 23 insertions(+), 22 deletions(-)\n> \n> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c\n> index 323c567cfb68..d10534de2da1 100644\n> --- a/accel/kvm/kvm-all.c\n> +++ b/accel/kvm/kvm-all.c\n> @@ -1533,7 +1533,7 @@ static void kvm_irqchip_create(MachineState *machine, KVMState *s)\n> */\n> static int kvm_recommended_vcpus(KVMState *s)\n> {\n> - int ret = kvm_check_extension(s, KVM_CAP_NR_VCPUS);\n> + int ret = kvm_vm_check_extension(s, KVM_CAP_NR_VCPUS);\n> return (ret) ? ret : 4;\n> }\n> \n> @@ -1623,27 +1623,6 @@ static int kvm_init(MachineState *ms)\n> s->nr_slots = 32;\n> }\n> \n> - /* check the vcpu limits */\n> - soft_vcpus_limit = kvm_recommended_vcpus(s);\n> - hard_vcpus_limit = kvm_max_vcpus(s);\n> -\n> - while (nc->name) {\n> - if (nc->num > soft_vcpus_limit) {\n> - fprintf(stderr,\n> - \"Warning: Number of %s cpus requested (%d) exceeds \"\n> - \"the recommended cpus supported by KVM (%d)\\n\",\n> - nc->name, nc->num, soft_vcpus_limit);\n> -\n> - if (nc->num > hard_vcpus_limit) {\n> - fprintf(stderr, \"Number of %s cpus requested (%d) exceeds \"\n> - \"the maximum cpus supported by KVM (%d)\\n\",\n> - nc->name, nc->num, hard_vcpus_limit);\n> - exit(1);\n> - }\n> - }\n> - nc++;\n> - }\n> -\n> kvm_type = qemu_opt_get(qemu_get_machine_opts(), \"kvm-type\");\n> if (mc->kvm_type) {\n> type = mc->kvm_type(kvm_type);\n> @@ -1678,6 +1657,28 @@ static int kvm_init(MachineState *ms)\n> }\n> \n> s->vmfd = ret;\n> +\n> + /* check the vcpu limits */\n> + soft_vcpus_limit = kvm_recommended_vcpus(s);\n> + hard_vcpus_limit = kvm_max_vcpus(s);\n> +\n> + while (nc->name) {\n> + if (nc->num > soft_vcpus_limit) {\n> + fprintf(stderr,\n> + \"Warning: Number of %s cpus requested (%d) exceeds \"\n> + \"the recommended cpus supported by KVM (%d)\\n\",\n> + nc->name, nc->num, soft_vcpus_limit);\n> +\n> + if (nc->num > hard_vcpus_limit) {\n> + fprintf(stderr, \"Number of %s cpus requested (%d) exceeds \"\n> + \"the maximum cpus supported by KVM (%d)\\n\",\n> + nc->name, nc->num, hard_vcpus_limit);\n> + exit(1);\n> + }\n> + }\n> + nc++;\n> + }\n> +\n> missing_cap = kvm_check_extension_list(s, kvm_required_capabilites);\n> if (!missing_cap) {\n> missing_cap =\n>","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@bilbo.ozlabs.org","Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=nongnu.org\n\t(client-ip=2001:4830:134:3::11; helo=lists.gnu.org;\n\tenvelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n\treceiver=)","ozlabs.org;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key;\n\tunprotected) header.d=gibson.dropbear.id.au\n\theader.i=@gibson.dropbear.id.au header.b=\"c1ucNGry\"; \n\tdkim-atps=neutral"],"Received":["from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11])\n\t(using TLSv1 with cipher AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby ozlabs.org (Postfix) with ESMTPS id 3xtgBj5p76z9sCZ\n\tfor ;\n\tFri, 15 Sep 2017 13:00:45 +1000 (AEST)","from localhost ([::1]:50877 helo=lists.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.71) (envelope-from\n\t)\n\tid 1dsgrz-0005XF-RC\n\tfor incoming@patchwork.ozlabs.org; Thu, 14 Sep 2017 23:00:43 -0400","from eggs.gnu.org ([2001:4830:134:3::10]:46620)\n\tby lists.gnu.org with esmtp (Exim 4.71)\n\t(envelope-from ) id 1dsgrC-0005WO-MV\n\tfor qemu-devel@nongnu.org; Thu, 14 Sep 2017 22:59:56 -0400","from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)\n\t(envelope-from ) id 1dsgrB-0002ZR-E7\n\tfor qemu-devel@nongnu.org; Thu, 14 Sep 2017 22:59:54 -0400","from ozlabs.org ([2401:3900:2:1::2]:54575)\n\tby eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32)\n\t(Exim 4.71) (envelope-from )\n\tid 1dsgrB-0002Yg-0w; Thu, 14 Sep 2017 22:59:53 -0400","by ozlabs.org (Postfix, from userid 1007)\n\tid 3xtg9d4ryhz9sCZ; Fri, 15 Sep 2017 12:59:49 +1000 (AEST)"],"DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple;\n\td=gibson.dropbear.id.au; s=201602; t=1505444389;\n\tbh=6kO0ctGDID0pCkYCV+JPtve8nZb7qB8LiAvc+Z9Sljo=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=c1ucNGryGxKGVzsxsgf+KXyrDcAbArgMcfLB2+hRb+D0mhqPzQdj5iNTKjtCMGuXr\n\tS2oUtkkco2iR/U5sYpElvwLUavmuN4vx/wh/JuDF3bsMTSEN0pI0wgz+Bcyxu/wnop\n\tiNr5dDfIGc+ohAoHIHIwnWL+bgUMeJTnBgmA4i30=","Date":"Fri, 15 Sep 2017 11:00:21 +1000","From":"David Gibson ","To":"Greg Kurz ","Message-ID":"<20170915010021.GC5250@umbus.fritz.box>","References":"<150541711102.1616.2690784964841960181.stgit@bahia.lan>\n\t<150541713284.1616.15291547955159941369.stgit@bahia.lan>","MIME-Version":"1.0","Content-Type":"multipart/signed; micalg=pgp-sha256;\n\tprotocol=\"application/pgp-signature\"; boundary=\"c3bfwLpm8qysLVxt\"","Content-Disposition":"inline","In-Reply-To":"<150541713284.1616.15291547955159941369.stgit@bahia.lan>","User-Agent":"Mutt/1.8.3 (2017-05-23)","X-detected-operating-system":"by eggs.gnu.org: Genre and OS details not\n\trecognized.","X-Received-From":"2401:3900:2:1::2","Subject":"Re: [Qemu-devel] [PATCH 2/3] kvm: check KVM_CAP_NR_VCPUS with\n\tkvm_vm_check_extension()","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.21","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Cc":"Paolo Bonzini , Thomas Huth ,\n\tqemu-ppc@nongnu.org, qemu-devel@nongnu.org,\n\tSam Bobroff ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"\"Qemu-devel\"\n\t"}},{"id":1768949,"web_url":"http://patchwork.ozlabs.org/comment/1768949/","msgid":"","list_archive_url":null,"date":"2017-09-15T05:34:59","subject":"Re: [Qemu-devel] [PATCH 2/3] kvm: check KVM_CAP_NR_VCPUS with\n\tkvm_vm_check_extension()","submitter":{"id":66152,"url":"http://patchwork.ozlabs.org/api/people/66152/","name":"Thomas Huth","email":"thuth@redhat.com"},"content":"On 14.09.2017 21:25, Greg Kurz wrote:\n> On a modern server-class ppc host with the following CPU topology:\n> \n> Architecture: ppc64le\n> Byte Order: Little Endian\n> CPU(s): 32\n> On-line CPU(s) list: 0,8,16,24\n> Off-line CPU(s) list: 1-7,9-15,17-23,25-31\n> Thread(s) per core: 1\n> \n> If both KVM PR and KVM HV loaded and we pass:\n> \n> -machine pseries,accel=kvm,kvm-type=PR -smp 8\n> \n> We expect QEMU to warn that this exceeds the number of online CPUs:\n> \n> Warning: Number of SMP cpus requested (8) exceeds the recommended\n> cpus supported by KVM (4)\n> Warning: Number of hotpluggable cpus requested (8) exceeds the\n> recommended cpus supported by KVM (4)\n> \n> but nothing is printed...\n> \n> This happens because on ppc the KVM_CAP_NR_VCPUS capability is VM\n> specific ndreally depends on the KVM type, but we currently use it\n> as a global capability. And KVM returns a fallback value based on\n> KVM HV being present. Maybe KVM on POWER shouldn't presume anything\n> as long as it doesn't have a VM, but in all cases, we should call\n> KVM_CREATE_VM first and use KVM_CAP_NR_VCPUS as a VM capability.\n> \n> This patch hence changes kvm_recommended_vcpus() accordingly and\n> moves the sanity checking of smp_cpus after the VM creation.\n> \n> It is okay for the other archs that also implement KVM_CAP_NR_VCPUS,\n> ie, mips, s390, x86 and arm, because they don't depend on the VM\n> being created or not.\n> \n> Signed-off-by: Greg Kurz \n> ---\n> accel/kvm/kvm-all.c | 45 +++++++++++++++++++++++----------------------\n> 1 file changed, 23 insertions(+), 22 deletions(-)\n> \n> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c\n> index 323c567cfb68..d10534de2da1 100644\n> --- a/accel/kvm/kvm-all.c\n> +++ b/accel/kvm/kvm-all.c\n> @@ -1533,7 +1533,7 @@ static void kvm_irqchip_create(MachineState *machine, KVMState *s)\n> */\n> static int kvm_recommended_vcpus(KVMState *s)\n> {\n> - int ret = kvm_check_extension(s, KVM_CAP_NR_VCPUS);\n> + int ret = kvm_vm_check_extension(s, KVM_CAP_NR_VCPUS);\n> return (ret) ? ret : 4;\n> }\n> \n> @@ -1623,27 +1623,6 @@ static int kvm_init(MachineState *ms)\n> s->nr_slots = 32;\n> }\n> \n> - /* check the vcpu limits */\n> - soft_vcpus_limit = kvm_recommended_vcpus(s);\n> - hard_vcpus_limit = kvm_max_vcpus(s);\n> -\n> - while (nc->name) {\n> - if (nc->num > soft_vcpus_limit) {\n> - fprintf(stderr,\n> - \"Warning: Number of %s cpus requested (%d) exceeds \"\n> - \"the recommended cpus supported by KVM (%d)\\n\",\n> - nc->name, nc->num, soft_vcpus_limit);\n> -\n> - if (nc->num > hard_vcpus_limit) {\n> - fprintf(stderr, \"Number of %s cpus requested (%d) exceeds \"\n> - \"the maximum cpus supported by KVM (%d)\\n\",\n> - nc->name, nc->num, hard_vcpus_limit);\n> - exit(1);\n> - }\n> - }\n> - nc++;\n> - }\n> -\n> kvm_type = qemu_opt_get(qemu_get_machine_opts(), \"kvm-type\");\n> if (mc->kvm_type) {\n> type = mc->kvm_type(kvm_type);\n> @@ -1678,6 +1657,28 @@ static int kvm_init(MachineState *ms)\n> }\n> \n> s->vmfd = ret;\n> +\n> + /* check the vcpu limits */\n> + soft_vcpus_limit = kvm_recommended_vcpus(s);\n> + hard_vcpus_limit = kvm_max_vcpus(s);\n> +\n> + while (nc->name) {\n> + if (nc->num > soft_vcpus_limit) {\n> + fprintf(stderr,\n> + \"Warning: Number of %s cpus requested (%d) exceeds \"\n> + \"the recommended cpus supported by KVM (%d)\\n\",\n> + nc->name, nc->num, soft_vcpus_limit);\n> +\n> + if (nc->num > hard_vcpus_limit) {\n> + fprintf(stderr, \"Number of %s cpus requested (%d) exceeds \"\n> + \"the maximum cpus supported by KVM (%d)\\n\",\n> + nc->name, nc->num, hard_vcpus_limit);\n> + exit(1);\n> + }\n> + }\n> + nc++;\n> + }\n> +\n> missing_cap = kvm_check_extension_list(s, kvm_required_capabilites);\n> if (!missing_cap) {\n> missing_cap =\n> \n\nReviewed-by: Thomas Huth ","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@bilbo.ozlabs.org","Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=nongnu.org\n\t(client-ip=2001:4830:134:3::11; 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