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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id h27sm22065673wmc.43.2021.11.15.08.04.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Nov 2021 08:04:02 -0800 (PST) From: Vitaly Kuznetsov To: Christian Borntraeger , Paolo Bonzini , kvm@vger.kernel.org Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Eduardo Habkost , Marc Zyngier , Andrew Jones , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Mackerras , Michael Ellerman , kvm-ppc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/5] KVM: Cap KVM_CAP_NR_VCPUS by KVM_CAP_MAX_VCPUS and re-purpose it on x86 In-Reply-To: References: <20211111162746.100598-1-vkuznets@redhat.com> <4a3c7be7-12fa-6e47-64eb-02e6c5be5dbc@redhat.com> Date: Mon, 15 Nov 2021 17:04:01 +0100 Message-ID: <877dd9pfri.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Christian Borntraeger writes: > Am 11.11.21 um 17:32 schrieb Paolo Bonzini: >> On 11/11/21 17:27, Vitaly Kuznetsov wrote: >>> This is a comtinuation of "KVM: x86: Drop arbitraty KVM_SOFT_MAX_VCPUS" >>> (https://lore.kernel.org/kvm/20211111134733.86601-1-vkuznets@redhat.com= /) >>> work. >>> >>> 1) Enforce KVM_CAP_NR_VCPUS <=3D KVM_CAP_MAX_VCPUS rule on all >>> =C2=A0 architectures. [Sean Christopherson] >>> 2) Make KVM_CAP_NR_VCPUS return num_online_cpus() and not an arbitrary >>> =C2=A0 value of '710' on x86. >>> >>> Everything but x86 was only 'eyeball tested', the change is trivial >>> but sorry in advance if I screwed up) >>=20 >> Christian, can you look at this for s390?=C2=A0 Returning a fixed value = seems wrong for KVM_CAP_NR_VCPUS. > > If we talk about recommended number, then num_online_cpus() also seems to= make sense on s390 so > if you change that for s390 as well I can ACK this. Thanks! For KVM_CAP_MAX_VCPUS s390 code returns one of the three things: KVM_S390_BSCA_CPU_SLOTS(64), KVM_MAX_VCPUS(255) or KVM_S390_ESCA_CPU_SLOTS(248). For KVM_CAP_NR_VCPUS, would it be better to return raw num_online_cpus(): diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 6a6dd5e1daf6..fcecbb762a1a 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -578,6 +578,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long = ext) r =3D MEM_OP_MAX_SIZE; break; case KVM_CAP_NR_VCPUS: + r =3D num_online_cpus(); + break; case KVM_CAP_MAX_VCPUS: case KVM_CAP_MAX_VCPU_ID: r =3D KVM_S390_BSCA_CPU_SLOTS; or cap KVM_CAP_MAX_VCPUS value with num_online_cpus(), e.g. diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 6a6dd5e1daf6..1cfe36f6432e 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -585,6 +585,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long = ext) r =3D KVM_MAX_VCPUS; else if (sclp.has_esca && sclp.has_64bscao) r =3D KVM_S390_ESCA_CPU_SLOTS; + if (ext =3D=3D KVM_CAP_NR_VCPUS) + r =3D min_t(unsigned int, num_online_cpus(), r); break; case KVM_CAP_S390_COW: r =3D MACHINE_HAS_ESOP; For reference, see our ARM discussion: https://lore.kernel.org/kvm/20211111162746.100598-2-vkuznets@redhat.com/ though 390's situation is different, the returned value for KVM_CAP_MAX_VCPUS is not VM-dependent. --=20 Vitaly From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1ADA3C433EF for ; Mon, 15 Nov 2021 16:24:28 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D7B2963211 for ; Mon, 15 Nov 2021 16:24:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org D7B2963211 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; 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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id h27sm22065673wmc.43.2021.11.15.08.04.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Nov 2021 08:04:02 -0800 (PST) From: Vitaly Kuznetsov To: Christian Borntraeger , Paolo Bonzini , kvm@vger.kernel.org Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Eduardo Habkost , Marc Zyngier , Andrew Jones , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Mackerras , Michael Ellerman , kvm-ppc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/5] KVM: Cap KVM_CAP_NR_VCPUS by KVM_CAP_MAX_VCPUS and re-purpose it on x86 In-Reply-To: References: <20211111162746.100598-1-vkuznets@redhat.com> <4a3c7be7-12fa-6e47-64eb-02e6c5be5dbc@redhat.com> Date: Mon, 15 Nov 2021 17:04:01 +0100 Message-ID: <877dd9pfri.fsf@redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=vkuznets@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211115_080412_988090_01DADE76 X-CRM114-Status: GOOD ( 13.37 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Q2hyaXN0aWFuIEJvcm50cmFlZ2VyIDxib3JudHJhZWdlckBkZS5pYm0uY29tPiB3cml0ZXM6Cgo+ IEFtIDExLjExLjIxIHVtIDE3OjMyIHNjaHJpZWIgUGFvbG8gQm9uemluaToKPj4gT24gMTEvMTEv MjEgMTc6MjcsIFZpdGFseSBLdXpuZXRzb3Ygd3JvdGU6Cj4+PiBUaGlzIGlzIGEgY29tdGludWF0 aW9uIG9mICJLVk06IHg4NjogRHJvcCBhcmJpdHJhdHkgS1ZNX1NPRlRfTUFYX1ZDUFVTIgo+Pj4g KGh0dHBzOi8vbG9yZS5rZXJuZWwub3JnL2t2bS8yMDIxMTExMTEzNDczMy44NjYwMS0xLXZrdXpu ZXRzQHJlZGhhdC5jb20vKQo+Pj4gd29yay4KPj4+Cj4+PiAxKSBFbmZvcmNlIEtWTV9DQVBfTlJf VkNQVVMgPD0gS1ZNX0NBUF9NQVhfVkNQVVMgcnVsZSBvbiBhbGwKPj4+IMKgIGFyY2hpdGVjdHVy ZXMuIFtTZWFuIENocmlzdG9waGVyc29uXQo+Pj4gMikgTWFrZSBLVk1fQ0FQX05SX1ZDUFVTIHJl dHVybiBudW1fb25saW5lX2NwdXMoKSBhbmQgbm90IGFuIGFyYml0cmFyeQo+Pj4gwqAgdmFsdWUg b2YgJzcxMCcgb24geDg2Lgo+Pj4KPj4+IEV2ZXJ5dGhpbmcgYnV0IHg4NiB3YXMgb25seSAnZXll YmFsbCB0ZXN0ZWQnLCB0aGUgY2hhbmdlIGlzIHRyaXZpYWwKPj4+IGJ1dCBzb3JyeSBpbiBhZHZh bmNlIGlmIEkgc2NyZXdlZCB1cCkKPj4gCj4+IENocmlzdGlhbiwgY2FuIHlvdSBsb29rIGF0IHRo aXMgZm9yIHMzOTA/wqAgUmV0dXJuaW5nIGEgZml4ZWQgdmFsdWUgc2VlbXMgd3JvbmcgZm9yIEtW TV9DQVBfTlJfVkNQVVMuCj4KPiBJZiB3ZSB0YWxrIGFib3V0IHJlY29tbWVuZGVkIG51bWJlciwg dGhlbiBudW1fb25saW5lX2NwdXMoKSBhbHNvIHNlZW1zIHRvIG1ha2Ugc2Vuc2Ugb24gczM5MCBz bwo+IGlmIHlvdSBjaGFuZ2UgdGhhdCBmb3IgczM5MCBhcyB3ZWxsIEkgY2FuIEFDSyB0aGlzLgoK VGhhbmtzIQoKRm9yIEtWTV9DQVBfTUFYX1ZDUFVTIHMzOTAgY29kZSByZXR1cm5zIG9uZSBvZiB0 aGUgdGhyZWUgdGhpbmdzOgpLVk1fUzM5MF9CU0NBX0NQVV9TTE9UUyg2NCksIEtWTV9NQVhfVkNQ VVMoMjU1KSBvcgpLVk1fUzM5MF9FU0NBX0NQVV9TTE9UUygyNDgpLgoKRm9yIEtWTV9DQVBfTlJf VkNQVVMsIHdvdWxkIGl0IGJlIGJldHRlciB0byByZXR1cm4gcmF3Cm51bV9vbmxpbmVfY3B1cygp OgoKZGlmZiAtLWdpdCBhL2FyY2gvczM5MC9rdm0va3ZtLXMzOTAuYyBiL2FyY2gvczM5MC9rdm0v a3ZtLXMzOTAuYwppbmRleCA2YTZkZDVlMWRhZjYuLmZjZWNiYjc2MmExYSAxMDA2NDQKLS0tIGEv YXJjaC9zMzkwL2t2bS9rdm0tczM5MC5jCisrKyBiL2FyY2gvczM5MC9rdm0va3ZtLXMzOTAuYwpA QCAtNTc4LDYgKzU3OCw4IEBAIGludCBrdm1fdm1faW9jdGxfY2hlY2tfZXh0ZW5zaW9uKHN0cnVj dCBrdm0gKmt2bSwgbG9uZyBleHQpCiAgICAgICAgICAgICAgICByID0gTUVNX09QX01BWF9TSVpF OwogICAgICAgICAgICAgICAgYnJlYWs7CiAgICAgICAgY2FzZSBLVk1fQ0FQX05SX1ZDUFVTOgor ICAgICAgICAgICAgICAgciA9IG51bV9vbmxpbmVfY3B1cygpOworICAgICAgICAgICAgICAgYnJl YWs7CiAgICAgICAgY2FzZSBLVk1fQ0FQX01BWF9WQ1BVUzoKICAgICAgICBjYXNlIEtWTV9DQVBf TUFYX1ZDUFVfSUQ6CiAgICAgICAgICAgICAgICByID0gS1ZNX1MzOTBfQlNDQV9DUFVfU0xPVFM7 CgpvciBjYXAgS1ZNX0NBUF9NQVhfVkNQVVMgdmFsdWUgd2l0aCBudW1fb25saW5lX2NwdXMoKSwg ZS5nLgoKZGlmZiAtLWdpdCBhL2FyY2gvczM5MC9rdm0va3ZtLXMzOTAuYyBiL2FyY2gvczM5MC9r dm0va3ZtLXMzOTAuYwppbmRleCA2YTZkZDVlMWRhZjYuLjFjZmUzNmY2NDMyZSAxMDA2NDQKLS0t IGEvYXJjaC9zMzkwL2t2bS9rdm0tczM5MC5jCisrKyBiL2FyY2gvczM5MC9rdm0va3ZtLXMzOTAu YwpAQCAtNTg1LDYgKzU4NSw4IEBAIGludCBrdm1fdm1faW9jdGxfY2hlY2tfZXh0ZW5zaW9uKHN0 cnVjdCBrdm0gKmt2bSwgbG9uZyBleHQpCiAgICAgICAgICAgICAgICAgICAgICAgIHIgPSBLVk1f TUFYX1ZDUFVTOwogICAgICAgICAgICAgICAgZWxzZSBpZiAoc2NscC5oYXNfZXNjYSAmJiBzY2xw Lmhhc182NGJzY2FvKQogICAgICAgICAgICAgICAgICAgICAgICByID0gS1ZNX1MzOTBfRVNDQV9D UFVfU0xPVFM7CisgICAgICAgICAgICAgICBpZiAoZXh0ID09IEtWTV9DQVBfTlJfVkNQVVMpCisg ICAgICAgICAgICAgICAgICAgICAgIHIgPSBtaW5fdCh1bnNpZ25lZCBpbnQsIG51bV9vbmxpbmVf Y3B1cygpLCByKTsKICAgICAgICAgICAgICAgIGJyZWFrOwogICAgICAgIGNhc2UgS1ZNX0NBUF9T MzkwX0NPVzoKICAgICAgICAgICAgICAgIHIgPSBNQUNISU5FX0hBU19FU09QOwoKRm9yIHJlZmVy ZW5jZSwgc2VlIG91ciBBUk0gZGlzY3Vzc2lvbjoKaHR0cHM6Ly9sb3JlLmtlcm5lbC5vcmcva3Zt LzIwMjExMTExMTYyNzQ2LjEwMDU5OC0yLXZrdXpuZXRzQHJlZGhhdC5jb20vCnRob3VnaCAzOTAn cyBzaXR1YXRpb24gaXMgZGlmZmVyZW50LCB0aGUgcmV0dXJuZWQgdmFsdWUgZm9yCktWTV9DQVBf TUFYX1ZDUFVTIGlzIG5vdCBWTS1kZXBlbmRlbnQuCgotLSAKVml0YWx5CgoKX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KbGludXgtYXJtLWtlcm5lbCBtYWls aW5nIGxpc3QKbGludXgtYXJtLWtlcm5lbEBsaXN0cy5pbmZyYWRlYWQub3JnCmh0dHA6Ly9saXN0 cy5pbmZyYWRlYWQub3JnL21haWxtYW4vbGlzdGluZm8vbGludXgtYXJtLWtlcm5lbAo= From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vitaly Kuznetsov Date: Mon, 15 Nov 2021 16:04:01 +0000 Subject: Re: [PATCH 0/5] KVM: Cap KVM_CAP_NR_VCPUS by KVM_CAP_MAX_VCPUS and re-purpose it on x86 Message-Id: <877dd9pfri.fsf@redhat.com> List-Id: References: <20211111162746.100598-1-vkuznets@redhat.com> <4a3c7be7-12fa-6e47-64eb-02e6c5be5dbc@redhat.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Christian Borntraeger , Paolo Bonzini , kvm@vger.kernel.org Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Eduardo Habkost , Marc Zyngier , Andrew Jones , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Mackerras , Michael Ellerman , kvm-ppc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Christian Borntraeger writes: > Am 11.11.21 um 17:32 schrieb Paolo Bonzini: >> On 11/11/21 17:27, Vitaly Kuznetsov wrote: >>> This is a comtinuation of "KVM: x86: Drop arbitraty KVM_SOFT_MAX_VCPUS" >>> (https://lore.kernel.org/kvm/20211111134733.86601-1-vkuznets@redhat.com/) >>> work. >>> >>> 1) Enforce KVM_CAP_NR_VCPUS <= KVM_CAP_MAX_VCPUS rule on all >>>   architectures. [Sean Christopherson] >>> 2) Make KVM_CAP_NR_VCPUS return num_online_cpus() and not an arbitrary >>>   value of '710' on x86. >>> >>> Everything but x86 was only 'eyeball tested', the change is trivial >>> but sorry in advance if I screwed up) >> >> Christian, can you look at this for s390?  Returning a fixed value seems wrong for KVM_CAP_NR_VCPUS. > > If we talk about recommended number, then num_online_cpus() also seems to make sense on s390 so > if you change that for s390 as well I can ACK this. Thanks! For KVM_CAP_MAX_VCPUS s390 code returns one of the three things: KVM_S390_BSCA_CPU_SLOTS(64), KVM_MAX_VCPUS(255) or KVM_S390_ESCA_CPU_SLOTS(248). For KVM_CAP_NR_VCPUS, would it be better to return raw num_online_cpus(): diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 6a6dd5e1daf6..fcecbb762a1a 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -578,6 +578,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = MEM_OP_MAX_SIZE; break; case KVM_CAP_NR_VCPUS: + r = num_online_cpus(); + break; case KVM_CAP_MAX_VCPUS: case KVM_CAP_MAX_VCPU_ID: r = KVM_S390_BSCA_CPU_SLOTS; or cap KVM_CAP_MAX_VCPUS value with num_online_cpus(), e.g. diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 6a6dd5e1daf6..1cfe36f6432e 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -585,6 +585,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = KVM_MAX_VCPUS; else if (sclp.has_esca && sclp.has_64bscao) r = KVM_S390_ESCA_CPU_SLOTS; + if (ext == KVM_CAP_NR_VCPUS) + r = min_t(unsigned int, num_online_cpus(), r); break; case KVM_CAP_S390_COW: r = MACHINE_HAS_ESOP; For reference, see our ARM discussion: https://lore.kernel.org/kvm/20211111162746.100598-2-vkuznets@redhat.com/ though 390's situation is different, the returned value for KVM_CAP_MAX_VCPUS is not VM-dependent. -- Vitaly