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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6FF52C433EF for ; Wed, 23 Feb 2022 10:02:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239458AbiBWKDW (ORCPT ); Wed, 23 Feb 2022 05:03:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56770 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236112AbiBWKDV (ORCPT ); Wed, 23 Feb 2022 05:03:21 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F0798A332 for ; Wed, 23 Feb 2022 02:02:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=xniVx7Xx+NhrCVAQM7GGmPMpzrOCc61gpKt3BTFhkb0=; b=kljlGBFEFOWPtmxANQaW9RPHID /QB2FGRTaClSA65aWNphuAbOxRhdlDCJiEkLSrySbVw0li5Rr0wfZJCexe7npnWsAiVahS+zvuhNK frHCFNuMOZ+DsY+44rQiecdVy2PAPVRMrsWqV5azVUE3TFzsuIw7Fql1BuE2o3x2neilFTc9hmDLJ qqFQpP0KfNKWkbM+GUAMhm+iRtE3Syk3udE0HkmYYM8bPN9F2gDctZwLyco9bG0ObP+dsfUk5qLDg yG7tzxpKQ/tHsmKfy7XGb1pI194y4BnzQP39HSSVVdH9bJPctkPDIVbuBHfTeuGBzlp/aXbmxGU92 Oy8fK1Kg==; Received: from [2001:8b0:10b:1::3ae] (helo=u3832b3a9db3152.ant.amazon.com) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nMoTu-003e66-7M; Wed, 23 Feb 2022 10:02:46 +0000 Message-ID: <8622beb5a721ae888f21c2e7c74fae23b2e2ccb6.camel@infradead.org> Subject: Re: [PATCH v8 7/7] KVM: x86: Expose TSC offset controls to userspace From: David Woodhouse To: Oliver Upton , kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Cc: Paolo Bonzini , Sean Christopherson , Marc Zyngier , Peter Shier , Jim Mattson , David Matlack , Ricardo Koller , Jing Zhang , Raghavendra Rao Anata , James Morse , Alexandru Elisei , Suzuki K Poulose , linux-arm-kernel@lists.infradead.org, Andrew Jones , Will Deacon , Catalin Marinas Date: Wed, 23 Feb 2022 10:02:44 +0000 In-Reply-To: <20210916181538.968978-8-oupton@google.com> References: <20210916181538.968978-1-oupton@google.com> <20210916181538.968978-8-oupton@google.com> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-Uo+/RJ9pVBZdWpqGNUDQ" User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org --=-Uo+/RJ9pVBZdWpqGNUDQ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2021-09-16 at 18:15 +0000, Oliver Upton wrote: > To date, VMM-directed TSC synchronization and migration has been a bit > messy. KVM has some baked-in heuristics around TSC writes to infer if > the VMM is attempting to synchronize. This is problematic, as it depends > on host userspace writing to the guest's TSC within 1 second of the last > write. >=20 > A much cleaner approach to configuring the guest's views of the TSC is to > simply migrate the TSC offset for every vCPU. Offsets are idempotent, > and thus not subject to change depending on when the VMM actually > reads/writes values from/to KVM. The VMM can then read the TSC once with > KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when > the guest is paused. >=20 > Cc: David Matlack > Cc: Sean Christopherson > Signed-off-by: Oliver Upton > --- > Documentation/virt/kvm/devices/vcpu.rst | 57 ++++++++++++ > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/include/uapi/asm/kvm.h | 4 + > arch/x86/kvm/x86.c | 110 ++++++++++++++++++++++++ > 4 files changed, 172 insertions(+) >=20 > diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt= /kvm/devices/vcpu.rst > index 2acec3b9ef65..3b399d727c11 100644 > --- a/Documentation/virt/kvm/devices/vcpu.rst > +++ b/Documentation/virt/kvm/devices/vcpu.rst > @@ -161,3 +161,60 @@ Specifies the base address of the stolen time struct= ure for this VCPU. The > base address must be 64 byte aligned and exist within a valid guest memo= ry > region. See Documentation/virt/kvm/arm/pvtime.rst for more information > including the layout of the stolen time structure. > + > +4. GROUP: KVM_VCPU_TSC_CTRL > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D > + > +:Architectures: x86 > + > +4.1 ATTRIBUTE: KVM_VCPU_TSC_OFFSET > + > +:Parameters: 64-bit unsigned TSC offset > + > +Returns: > + > + =3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + -EFAULT Error reading/writing the provided > + parameter address. > + -ENXIO Attribute not supported > + =3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + > +Specifies the guest's TSC offset relative to the host's TSC. The guest's > +TSC is then derived by the following equation: > + > + guest_tsc =3D host_tsc + KVM_VCPU_TSC_OFFSET This isn't true. 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<8622beb5a721ae888f21c2e7c74fae23b2e2ccb6.camel@infradead.org> Subject: Re: [PATCH v8 7/7] KVM: x86: Expose TSC offset controls to userspace From: David Woodhouse To: Oliver Upton , kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Cc: Paolo Bonzini , Sean Christopherson , Marc Zyngier , Peter Shier , Jim Mattson , David Matlack , Ricardo Koller , Jing Zhang , Raghavendra Rao Anata , James Morse , Alexandru Elisei , Suzuki K Poulose , linux-arm-kernel@lists.infradead.org, Andrew Jones , Will Deacon , Catalin Marinas Date: Wed, 23 Feb 2022 10:02:44 +0000 In-Reply-To: <20210916181538.968978-8-oupton@google.com> References: <20210916181538.968978-1-oupton@google.com> <20210916181538.968978-8-oupton@google.com> User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html 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: multipart/mixed; boundary="===============7256362639566991981==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============7256362639566991981== Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-Uo+/RJ9pVBZdWpqGNUDQ" --=-Uo+/RJ9pVBZdWpqGNUDQ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2021-09-16 at 18:15 +0000, Oliver Upton wrote: > To date, VMM-directed TSC synchronization and migration has been a bit > messy. KVM has some baked-in heuristics around TSC writes to infer if > the VMM is attempting to synchronize. This is problematic, as it depends > on host userspace writing to the guest's TSC within 1 second of the last > write. >=20 > A much cleaner approach to configuring the guest's views of the TSC is to > simply migrate the TSC offset for every vCPU. Offsets are idempotent, > and thus not subject to change depending on when the VMM actually > reads/writes values from/to KVM. The VMM can then read the TSC once with > KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when > the guest is paused. >=20 > Cc: David Matlack > Cc: Sean Christopherson > Signed-off-by: Oliver Upton > --- > Documentation/virt/kvm/devices/vcpu.rst | 57 ++++++++++++ > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/include/uapi/asm/kvm.h | 4 + > arch/x86/kvm/x86.c | 110 ++++++++++++++++++++++++ > 4 files changed, 172 insertions(+) >=20 > diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt= /kvm/devices/vcpu.rst > index 2acec3b9ef65..3b399d727c11 100644 > --- a/Documentation/virt/kvm/devices/vcpu.rst > +++ b/Documentation/virt/kvm/devices/vcpu.rst > @@ -161,3 +161,60 @@ Specifies the base address of the stolen time struct= ure for this VCPU. The > base address must be 64 byte aligned and exist within a valid guest memo= ry > region. See Documentation/virt/kvm/arm/pvtime.rst for more information > including the layout of the stolen time structure. > + > +4. GROUP: KVM_VCPU_TSC_CTRL > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D > + > +:Architectures: x86 > + > +4.1 ATTRIBUTE: KVM_VCPU_TSC_OFFSET > + > +:Parameters: 64-bit unsigned TSC offset > + > +Returns: > + > + =3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + -EFAULT Error reading/writing the provided > + parameter address. > + -ENXIO Attribute not supported > + =3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + > +Specifies the guest's TSC offset relative to the host's TSC. The guest's > +TSC is then derived by the following equation: > + > + guest_tsc =3D host_tsc + KVM_VCPU_TSC_OFFSET This isn't true. 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port 10024) with ESMTP id P1FvSamwQFkO for ; Wed, 23 Feb 2022 05:02:54 -0500 (EST) Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 085F64C457 for ; Wed, 23 Feb 2022 05:02:53 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=xniVx7Xx+NhrCVAQM7GGmPMpzrOCc61gpKt3BTFhkb0=; b=kljlGBFEFOWPtmxANQaW9RPHID /QB2FGRTaClSA65aWNphuAbOxRhdlDCJiEkLSrySbVw0li5Rr0wfZJCexe7npnWsAiVahS+zvuhNK frHCFNuMOZ+DsY+44rQiecdVy2PAPVRMrsWqV5azVUE3TFzsuIw7Fql1BuE2o3x2neilFTc9hmDLJ qqFQpP0KfNKWkbM+GUAMhm+iRtE3Syk3udE0HkmYYM8bPN9F2gDctZwLyco9bG0ObP+dsfUk5qLDg yG7tzxpKQ/tHsmKfy7XGb1pI194y4BnzQP39HSSVVdH9bJPctkPDIVbuBHfTeuGBzlp/aXbmxGU92 Oy8fK1Kg==; Received: from [2001:8b0:10b:1::3ae] (helo=u3832b3a9db3152.ant.amazon.com) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nMoTu-003e66-7M; Wed, 23 Feb 2022 10:02:46 +0000 Message-ID: <8622beb5a721ae888f21c2e7c74fae23b2e2ccb6.camel@infradead.org> Subject: Re: [PATCH v8 7/7] KVM: x86: Expose TSC offset controls to userspace From: David Woodhouse To: Oliver Upton , kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Date: Wed, 23 Feb 2022 10:02:44 +0000 In-Reply-To: <20210916181538.968978-8-oupton@google.com> References: <20210916181538.968978-1-oupton@google.com> <20210916181538.968978-8-oupton@google.com> User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html X-Mailman-Approved-At: Wed, 23 Feb 2022 06:02:29 -0500 Cc: Catalin Marinas , Will Deacon , Marc Zyngier , Peter Shier , David Matlack , Paolo Bonzini , linux-arm-kernel@lists.infradead.org, Jim Mattson X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============1781136156672486138==" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu --===============1781136156672486138== Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-Uo+/RJ9pVBZdWpqGNUDQ" --=-Uo+/RJ9pVBZdWpqGNUDQ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2021-09-16 at 18:15 +0000, Oliver Upton wrote: > To date, VMM-directed TSC synchronization and migration has been a bit > messy. KVM has some baked-in heuristics around TSC writes to infer if > the VMM is attempting to synchronize. This is problematic, as it depends > on host userspace writing to the guest's TSC within 1 second of the last > write. >=20 > A much cleaner approach to configuring the guest's views of the TSC is to > simply migrate the TSC offset for every vCPU. Offsets are idempotent, > and thus not subject to change depending on when the VMM actually > reads/writes values from/to KVM. The VMM can then read the TSC once with > KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when > the guest is paused. >=20 > Cc: David Matlack > Cc: Sean Christopherson > Signed-off-by: Oliver Upton > --- > Documentation/virt/kvm/devices/vcpu.rst | 57 ++++++++++++ > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/include/uapi/asm/kvm.h | 4 + > arch/x86/kvm/x86.c | 110 ++++++++++++++++++++++++ > 4 files changed, 172 insertions(+) >=20 > diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt= /kvm/devices/vcpu.rst > index 2acec3b9ef65..3b399d727c11 100644 > --- a/Documentation/virt/kvm/devices/vcpu.rst > +++ b/Documentation/virt/kvm/devices/vcpu.rst > @@ -161,3 +161,60 @@ Specifies the base address of the stolen time struct= ure for this VCPU. The > base address must be 64 byte aligned and exist within a valid guest memo= ry > region. See Documentation/virt/kvm/arm/pvtime.rst for more information > including the layout of the stolen time structure. > + > +4. GROUP: KVM_VCPU_TSC_CTRL > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D > + > +:Architectures: x86 > + > +4.1 ATTRIBUTE: KVM_VCPU_TSC_OFFSET > + > +:Parameters: 64-bit unsigned TSC offset > + > +Returns: > + > + =3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + -EFAULT Error reading/writing the provided > + parameter address. > + -ENXIO Attribute not supported > + =3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + > +Specifies the guest's TSC offset relative to the host's TSC. The guest's > +TSC is then derived by the following equation: > + > + guest_tsc =3D host_tsc + KVM_VCPU_TSC_OFFSET This isn't true. The guest TSC also depends on the *scaling* factor. --=-Uo+/RJ9pVBZdWpqGNUDQ Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCEkQw ggYQMIID+KADAgECAhBNlCwQ1DvglAnFgS06KwZPMA0GCSqGSIb3DQEBDAUAMIGIMQswCQYDVQQG EwJVUzETMBEGA1UECBMKTmV3IEplcnNleTEUMBIGA1UEBxMLSmVyc2V5IENpdHkxHjAcBgNVBAoT FVRoZSBVU0VSVFJVU1QgTmV0d29yazEuMCwGA1UEAxMlVVNFUlRydXN0IFJTQSBDZXJ0aWZpY2F0 aW9uIEF1dGhvcml0eTAeFw0xODExMDIwMDAwMDBaFw0zMDEyMzEyMzU5NTlaMIGWMQswCQYDVQQG EwJHQjEbMBkGA1UECBMSR3JlYXRlciBNYW5jaGVzdGVyMRAwDgYDVQQHEwdTYWxmb3JkMRgwFgYD VQQKEw9TZWN0aWdvIExpbWl0ZWQxPjA8BgNVBAMTNVNlY3RpZ28gUlNBIENsaWVudCBBdXRoZW50 aWNhdGlvbiBhbmQgU2VjdXJlIEVtYWlsIENBMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKC AQEAyjztlApB/975Rrno1jvm2pK/KxBOqhq8gr2+JhwpKirSzZxQgT9tlC7zl6hn1fXjSo5MqXUf ItMltrMaXqcESJuK8dtK56NCSrq4iDKaKq9NxOXFmqXX2zN8HHGjQ2b2Xv0v1L5Nk1MQPKA19xeW 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