From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Morse Subject: Re: [PATCH v3 1/3] arm64: kvm: support kvmtool to detect RAS extension feature Date: Thu, 04 May 2017 16:49:07 +0100 Message-ID: <590B4D73.60000@arm.com> References: <1493530677-4919-1-git-send-email-gengdongjiu@huawei.com> <5908A5BC.1060202@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: mtsirkin@redhat.com, kvm@vger.kernel.org, tbaicar@codeaurora.org, qemu-devel@nongnu.org, wangxiongfeng2@huawei.com, ben@skyportsystems.com, linux@armlinux.org.uk, kvmarm@lists.cs.columbia.edu, huangshaoyu@huawei.com, lersek@redhat.com, songwenjun@huawei.com, wuquanming@huawei.com, marc.zyngier@arm.com, qemu-arm@nongnu.org, imammedo@redhat.com, linux-arm-kernel@lists.infradead.org, ard.biesheuvel@linaro.org, pbonzini@redhat.com To: Dongjiu Geng Return-path: In-Reply-To: <5908A5BC.1060202@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org Hi Dongjiu Geng, On 02/05/17 16:29, James Morse wrote: > I think we need a new API for injecting SError for SEI from Qemu/kvmtool, but it > shouldn't be related to the RAS extensions. All v8.0 CPUs have HCR_EL2.VSE, so > we need to know KVM supports this API. Thinking about this some more, it is slightly more nuanced, KVM can always provide an API to inject SError, but it can only set the VSESR if the CPU has the RAS Extensions. Only offering the inject-SError API call if we can also set the VSESR looks a bit funny, but no-one has needed the no-ESR version so far. I still don't think we should let user-space make the 'RAS Extensions means VSESR' logical step. So my comments on this patch become: Don't read id registers directly, use cpus_have_cap() which handles features that differ across CPUs or were turned off at compile time. Please don't call this 'KVM_CAP_ARM_RAS_EXTENSION', if we are building an API to inject SError, call it that instead. Thanks, James From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37084) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d6J0n-0002ki-RM for qemu-devel@nongnu.org; Thu, 04 May 2017 11:49:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d6J0n-0003e2-0l for qemu-devel@nongnu.org; Thu, 04 May 2017 11:49:49 -0400 Message-ID: <590B4D73.60000@arm.com> Date: Thu, 04 May 2017 16:49:07 +0100 From: James Morse MIME-Version: 1.0 References: <1493530677-4919-1-git-send-email-gengdongjiu@huawei.com> <5908A5BC.1060202@arm.com> In-Reply-To: <5908A5BC.1060202@arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v3 1/3] arm64: kvm: support kvmtool to detect RAS extension feature List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Dongjiu Geng Cc: marc.zyngier@arm.com, christoffer.dall@linaro.org, rkrcmar@redhat.com, linux@armlinux.org.uk, tbaicar@codeaurora.org, imammedo@redhat.com, zhaoshenglong@huawei.com, peter.maydell@linaro.org, pbonzini@redhat.com, qemu-devel@nongnu.org, qemu-arm@nongnu.org, lersek@redhat.com, ard.biesheuvel@linaro.org, mtsirkin@redhat.com, drjones@redhat.com, ben@skyportsystems.com, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, xiexiuqi@huawei.com, wangxiongfeng2@huawei.com, songwenjun@huawei.com, wuquanming@huawei.com, huangshaoyu@huawei.com Hi Dongjiu Geng, On 02/05/17 16:29, James Morse wrote: > I think we need a new API for injecting SError for SEI from Qemu/kvmtool, but it > shouldn't be related to the RAS extensions. All v8.0 CPUs have HCR_EL2.VSE, so > we need to know KVM supports this API. Thinking about this some more, it is slightly more nuanced, KVM can always provide an API to inject SError, but it can only set the VSESR if the CPU has the RAS Extensions. Only offering the inject-SError API call if we can also set the VSESR looks a bit funny, but no-one has needed the no-ESR version so far. I still don't think we should let user-space make the 'RAS Extensions means VSESR' logical step. So my comments on this patch become: Don't read id registers directly, use cpus_have_cap() which handles features that differ across CPUs or were turned off at compile time. Please don't call this 'KVM_CAP_ARM_RAS_EXTENSION', if we are building an API to inject SError, call it that instead. Thanks, James From mboxrd@z Thu Jan 1 00:00:00 1970 From: james.morse@arm.com (James Morse) Date: Thu, 04 May 2017 16:49:07 +0100 Subject: [PATCH v3 1/3] arm64: kvm: support kvmtool to detect RAS extension feature In-Reply-To: <5908A5BC.1060202@arm.com> References: <1493530677-4919-1-git-send-email-gengdongjiu@huawei.com> <5908A5BC.1060202@arm.com> Message-ID: <590B4D73.60000@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Dongjiu Geng, On 02/05/17 16:29, James Morse wrote: > I think we need a new API for injecting SError for SEI from Qemu/kvmtool, but it > shouldn't be related to the RAS extensions. All v8.0 CPUs have HCR_EL2.VSE, so > we need to know KVM supports this API. Thinking about this some more, it is slightly more nuanced, KVM can always provide an API to inject SError, but it can only set the VSESR if the CPU has the RAS Extensions. Only offering the inject-SError API call if we can also set the VSESR looks a bit funny, but no-one has needed the no-ESR version so far. I still don't think we should let user-space make the 'RAS Extensions means VSESR' logical step. So my comments on this patch become: Don't read id registers directly, use cpus_have_cap() which handles features that differ across CPUs or were turned off at compile time. Please don't call this 'KVM_CAP_ARM_RAS_EXTENSION', if we are building an API to inject SError, call it that instead. Thanks, James