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Tue, 01 Dec 2020 11:50:00 +0000 MIME-Version: 1.0 Date: Tue, 01 Dec 2020 11:50:00 +0000 From: Marc Zyngier To: Shenming Lu Subject: Re: [RFC PATCH v1 3/4] KVM: arm64: GICv4.1: Restore VLPI's pending state to physical side In-Reply-To: <9b80d460-e149-20c8-e9b3-e695310b4ed1@huawei.com> References: <20201123065410.1915-1-lushenming@huawei.com> <20201123065410.1915-4-lushenming@huawei.com> <5c724bb83730cdd5dcf7add9a812fa92@kernel.org> <2d2bcae4f871d239a1af50362f5c11a4@kernel.org> <49610291-cf57-ff78-d0ac-063af24efbb4@huawei.com> <48c10467-30f3-9b5c-bbcb-533a51516dc5@huawei.com> <2ad38077300bdcaedd2e3b073cd36743@kernel.org> <9b80d460-e149-20c8-e9b3-e695310b4ed1@huawei.com> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <274dafb2e21f49326a64bb575e668793@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: lushenming@huawei.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, eric.auger@redhat.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, christoffer.dall@arm.com, alex.williamson@redhat.com, kwankhede@nvidia.com, cohuck@redhat.com, cjia@nvidia.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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201201_065004_292737_ABB1B425 X-CRM114-Status: GOOD ( 16.63 ) 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: Neo Jia , kvm@vger.kernel.org, Suzuki K Poulose , Cornelia Huck , linux-kernel@vger.kernel.org, Kirti Wankhede , Christoffer Dall , Eric Auger , Alex Williamson , James Morse , Julien Thierry , yuzenghui@huawei.com, wanghaibin.wang@huawei.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2020-12-01 11:40, Shenming Lu wrote: > On 2020/12/1 18:55, Marc Zyngier wrote: >> On 2020-11-30 07:23, Shenming Lu wrote: >> >> Hi Shenming, >> >>> We are pondering over this problem these days, but still don't get a >>> good solution... >>> Could you give us some advice on this? >>> >>> Or could we move the restoring of the pending states (include the >>> sync >>> from guest RAM and the transfer to HW) to the GIC VM state change >>> handler, >>> which is completely corresponding to save_pending_tables (more >>> symmetric?) >>> and don't expose GICv4... >> >> What is "the GIC VM state change handler"? Is that a QEMU thing? > > Yeah, it is a a QEMU thing... > >> We don't really have that concept in KVM, so I'd appreciate if you >> could >> be a bit more explicit on this. > > My thought is to add a new interface (to QEMU) for the restoring of > the pending states, which is completely corresponding to > KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES... > And it is called from the GIC VM state change handler in QEMU, which > is happening after the restoring (call kvm_vgic_v4_set_forwarding()) > but before the starting (running) of the VFIO device. Right, that makes sense. I still wonder how much the GIC save/restore stuff differs from other architectures that implement similar features, such as x86 with VT-D. It is obviously too late to change the userspace interface, but I wonder whether we missed something at the time. Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel