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Tue, 11 Aug 2020 08:49:08 +0100 MIME-Version: 1.0 Date: Tue, 11 Aug 2020 08:49:08 +0100 From: Marc Zyngier To: Jingyi Wang Subject: Re: [kvm-unit-tests PATCH v3 00/10] arm/arm64: Add IPI/LPI/vtimer latency test In-Reply-To: <54de9edf-3cca-f968-1ea8-027556b5f5ff@huawei.com> References: <20200731074244.20432-1-wangjingyi11@huawei.com> <957a4657-7e17-b173-ea4d-10c29ab9e3cd@huawei.com> <0bd81d1da9040fce660af46763507ac2@kernel.org> <54de9edf-3cca-f968-1ea8-027556b5f5ff@huawei.com> User-Agent: Roundcube Webmail/1.4.5 Message-ID: X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: wangjingyi11@huawei.com, drjones@redhat.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, eric.auger@redhat.com, wanghaibin.wang@huawei.com, yuzenghui@huawei.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu 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-Transfer-Encoding: base64 Content-Type: text/plain; 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Tue, 11 Aug 2020 07:49:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597132150; bh=IUPcw48csQBeWPj+tDEVEv+3O8+8xdOT0GWWmV3xhXw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=p6JHJtSkOAuL9lUt8UMmNp2FiD+cO71u9hYD09Cqu9Klj1htM/inD+5+Tfs7CkEUY M8QhF+hGH0Y7EnehjjPZMoXWrkLP/77UNyPf1BI75ackInMB3a8SV+XFnriOHZ2aUL j5ygXxbHlSJ5/n4+yROoGpqyrrPymoy5wPBXhl8Y= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1k5P1w-001EIN-8x; Tue, 11 Aug 2020 08:49:08 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Tue, 11 Aug 2020 08:49:08 +0100 From: Marc Zyngier To: Jingyi Wang Cc: drjones@redhat.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, eric.auger@redhat.com, wanghaibin.wang@huawei.com, yuzenghui@huawei.com Subject: Re: [kvm-unit-tests PATCH v3 00/10] arm/arm64: Add IPI/LPI/vtimer latency test In-Reply-To: <54de9edf-3cca-f968-1ea8-027556b5f5ff@huawei.com> References: <20200731074244.20432-1-wangjingyi11@huawei.com> <957a4657-7e17-b173-ea4d-10c29ab9e3cd@huawei.com> <0bd81d1da9040fce660af46763507ac2@kernel.org> <54de9edf-3cca-f968-1ea8-027556b5f5ff@huawei.com> User-Agent: Roundcube Webmail/1.4.5 Message-ID: X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: wangjingyi11@huawei.com, drjones@redhat.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, eric.auger@redhat.com, wanghaibin.wang@huawei.com, yuzenghui@huawei.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 2020-08-11 02:48, Jingyi Wang wrote: > Hi Marc, > > On 8/5/2020 8:13 PM, Marc Zyngier wrote: >> On 2020-08-05 12:54, Jingyi Wang wrote: >>> Hi all, >>> >>> Currently, kvm-unit-tests only support GICv3 vLPI injection. May I >>> ask >>> is there any plan or suggestion on constructing irq bypass mechanism >>> to test vLPI direct injection in kvm-unit-tests? >> >> I'm not sure what you are asking for here. VLPIs are only delivered >> from a HW device, and the offloading mechanism isn't visible from >> userspace (you either have an enabled GICv4 implementation, or >> you don't). >> >> There are ways to *trigger* device MSIs from userspace and inject >> them in a guest, but that's only a debug feature, which shouldn't >> be enabled on a production system. >> >>         M. > > Sorry for the late reply. > > As I mentioned before, we want to add vLPI direct injection test > in KUT, meanwhile measure the latency of hardware vLPI injection. > > Sure, vLPI is triggered by hardware. Since kernel supports sending > ITS INT command in guest to trigger vLPI, I wonder if it is possible So can the host. > to add an extra interface to make a vLPI hardware-offload(just as > kvm_vgic_v4_set_forwarding() does). If so, vgic_its_trigger_msi() > can inject vLPI directly instead of using LR. The interface exists, it is in debugfs. But it mandates that the device exists. And no, I am not willing to add an extra KVM userspace API for this. The whole concept of injecting an INT to measure the performance of GICv4 is slightly bonkers, actually. Most of the cost is paid on the injection path (queuing a pair of command, waiting until the ITS wakes up and generate the signal...). What you really want to measure is the time from generation of the LPI by a device until the guest acknowledges the interrupt to the device itself. and this can only be implemented in the device. M. -- Jazz is not dead. It just smells funny...