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Fri, 28 Feb 2020 19:16:42 +0000 MIME-Version: 1.0 Date: Fri, 28 Feb 2020 19:16:42 +0000 From: Marc Zyngier To: Zenghui Yu Subject: Re: [PATCH v4 16/20] KVM: arm64: GICv4.1: Allow SGIs to switch between HW and SW interrupts In-Reply-To: <6798eb13-a7e9-2a92-91b2-9b657962ea79@huawei.com> References: <20200214145736.18550-1-maz@kernel.org> <20200214145736.18550-17-maz@kernel.org> <6798eb13-a7e9-2a92-91b2-9b657962ea79@huawei.com> Message-ID: <7aa668a5920b8deb8c2ee2fec3ef69b3@kernel.org> X-Sender: maz@kernel.org User-Agent: Roundcube Webmail/1.3.10 X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: yuzenghui@huawei.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, lorenzo.pieralisi@arm.com, jason@lakedaemon.net, rrichter@marvell.com, tglx@linutronix.de, eric.auger@redhat.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.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-20200228_111644_991824_99AC8076 X-CRM114-Status: GOOD ( 15.15 ) 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: Lorenzo Pieralisi , Jason Cooper , kvm@vger.kernel.org, Suzuki K Poulose , linux-kernel@vger.kernel.org, Eric Auger , Robert Richter , James Morse , Julien Thierry , Thomas Gleixner , 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+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Zenghui, On 2020-02-20 03:55, Zenghui Yu wrote: > Hi Marc, > > On 2020/2/14 22:57, Marc Zyngier wrote: >> In order to let a guest buy in the new, active-less SGIs, we >> need to be able to switch between the two modes. >> >> Handle this by stopping all guest activity, transfer the state >> from one mode to the other, and resume the guest. >> >> Signed-off-by: Marc Zyngier > > [...] > >> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c >> index 1bc09b523486..2c9fc13e2c59 100644 >> --- a/virt/kvm/arm/vgic/vgic-v3.c >> +++ b/virt/kvm/arm/vgic/vgic-v3.c >> @@ -540,6 +540,8 @@ int vgic_v3_map_resources(struct kvm *kvm) >> goto out; >> } >> + if (kvm_vgic_global_state.has_gicv4_1) >> + vgic_v4_configure_vsgis(kvm); >> dist->ready = true; >> out: > > Is there any reason to invoke vgic_v4_configure_vsgis() here? > This is called on the first VCPU run, through kvm_vgic_map_resources(). > Shouldn't the vSGI configuration only driven by a GICD_CTLR.nASSGIreq > writing (from guest, or from userspace maybe)? What I'm trying to catch here is the guest that has been restored with nASSGIreq set. At the moment, we don't do anything on the userspace side, because the vmm could decide to write that particular bit multiple times, and switching between the two modes is expensive (not to mention that all the vcpus may not have been created yet). Moving it to the first run makes all these pitfalls go away (we have the final nASSSGIreq value, and all the vcpus are accounted for). Does this make sense to you? 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