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([2001:b07:6468:f312:9541:9439:cb0f:89c]) by smtp.gmail.com with ESMTPSA id g195sm8807093wme.38.2020.07.10.02.38.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Jul 2020 02:38:13 -0700 (PDT) Subject: Re: [Question] How to testing SDEI client driver To: Gavin Shan , James Morse References: <8cdef8ea-e550-ccff-2041-526d6f6fcda0@redhat.com> <3cc7e69c-9315-5138-85f7-7b36e17b67a1@redhat.com> <2b5ef5b2-cf6b-3f4e-4250-c1d0a34e9873@arm.com> <69ecf58f-bf9d-6c2d-37ab-4397b30fff4b@redhat.com> <7c234a0a-3a64-b893-cb40-4b5cca865beb@redhat.com> <8d4e5f61-48db-1a02-2712-52e72801b241@arm.com> <0698199d-c84c-c923-e665-e09d5b83ba66@redhat.com> From: Paolo Bonzini Message-ID: <098f56da-bcb9-42e6-10cc-f1df90f28ec1@redhat.com> Date: Fri, 10 Jul 2020 11:38:12 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <0698199d-c84c-c923-e665-e09d5b83ba66@redhat.com> Content-Language: en-US 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-20200710_053819_036911_9E639C43 X-CRM114-Status: GOOD ( 13.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, maz@kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 10/07/20 11:08, Gavin Shan wrote: > Ok, thanks for the information, which makes thing much more clear. > So SDEI_EVENT_COMPLETE/AND_RESUME is issued depending if current > process can be rescheduled. I think it's Paolo's idea? Yes. :) >> The problem is invoking this whole thing when the guest can't do >> anything about it, because it can't schedule(). You can't know this >> from outside the guest. > > Yes, the interrupted process can't call schedule() before > SDEI_EVENT_COMPLETE at least because the SDEI event handler has to > finish as quick as possible. > > [...] we might figure out one > way to insert the schedule() by the SDEI event handler. I think you could do smp_send_reschedule(smp_processor_id()) before invoking SDEI_EVENT_COMPLETE_AND_RESUME. As James said, after the hypervisor processes SDEI_EVENT_COMPLETE_AND_RESUME the exit will be through the reschedule interrupt. Instead if the hypervisor sees SDEI_EVENT_COMPLETE it will wait for synchronous page-in to complete, remove the async page fault from its data structures, and resume execution. Paolo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel