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[80.210.64.78]) by smtp.gmail.com with ESMTPSA id 26sm8374578eds.67.2017.12.04.12.05.09 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 04 Dec 2017 12:05:09 -0800 (PST) From: Christoffer Dall To: kvmarm@lists.cs.columbia.edu Subject: [PATCH v6 2/8] KVM: arm/arm64: Factor out functionality to get vgic mmio requester_vcpu Date: Mon, 4 Dec 2017 21:05:00 +0100 Message-Id: <20171204200506.3224-3-cdall@kernel.org> X-Mailer: git-send-email 2.14.2 In-Reply-To: <20171204200506.3224-1-cdall@kernel.org> References: <20171204200506.3224-1-cdall@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20171204_120532_259785_78B68B45 X-CRM114-Status: GOOD ( 16.23 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, Marc Zyngier , Andre Przywara , Eric Auger , linux-arm-kernel@lists.infradead.org, Christoffer Dall MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP From: Christoffer Dall We are about to distinguish between userspace accesses and mmio traps for a number of the mmio handlers. When the requester vcpu is NULL, it mens we are handling a userspace acccess. Factor out the functionality to get the request vcpu into its own function, mostly so we have a common place to document the semantics of the return value. Also take the chance to move the functionality outside of holding a spinlock and instead explicitly disable and enable preemption. This supports PREEMPT_RT kernels as well. Acked-by: Marc Zyngier Reviewed-by: Andre Przywara Signed-off-by: Christoffer Dall --- virt/kvm/arm/vgic/vgic-mmio.c | 44 +++++++++++++++++++++++++++---------------- 1 file changed, 28 insertions(+), 16 deletions(-) diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c index deb51ee16a3d..747b0a3b4784 100644 --- a/virt/kvm/arm/vgic/vgic-mmio.c +++ b/virt/kvm/arm/vgic/vgic-mmio.c @@ -122,6 +122,27 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu, return value; } +/* + * This function will return the VCPU that performed the MMIO access and + * trapped from twithin the VM, and will return NULL if this is a userspace + * access. + * + * We can disable preemption locally around accessing the per-CPU variable, + * and use the resolved vcpu pointer after enabling preemption again, because + * even if the current thread is migrated to another CPU, reading the per-CPU + * value later will give us the same value as we update the per-CPU variable + * in the preempt notifier handlers. + */ +static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void) +{ + struct kvm_vcpu *vcpu; + + preempt_disable(); + vcpu = kvm_arm_get_running_vcpu(); + preempt_enable(); + return vcpu; +} + void vgic_mmio_write_spending(struct kvm_vcpu *vcpu, gpa_t addr, unsigned int len, unsigned long val) @@ -184,24 +205,10 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu, static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq, bool new_active_state) { - struct kvm_vcpu *requester_vcpu; unsigned long flags; - spin_lock_irqsave(&irq->irq_lock, flags); + struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu(); - /* - * The vcpu parameter here can mean multiple things depending on how - * this function is called; when handling a trap from the kernel it - * depends on the GIC version, and these functions are also called as - * part of save/restore from userspace. - * - * Therefore, we have to figure out the requester in a reliable way. - * - * When accessing VGIC state from user space, the requester_vcpu is - * NULL, which is fine, because we guarantee that no VCPUs are running - * when accessing VGIC state from user space so irq->vcpu->cpu is - * always -1. - */ - requester_vcpu = kvm_arm_get_running_vcpu(); + spin_lock_irqsave(&irq->irq_lock, flags); /* * If this virtual IRQ was written into a list register, we @@ -213,6 +220,11 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq, * vgic_change_active_prepare) and still has to sync back this IRQ, * so we release and re-acquire the spin_lock to let the other thread * sync back the IRQ. + * + * When accessing VGIC state from user space, requester_vcpu is + * NULL, which is fine, because we guarantee that no VCPUs are running + * when accessing VGIC state from user space so irq->vcpu->cpu is + * always -1. */ while (irq->vcpu && /* IRQ may have state in an LR somewhere */ irq->vcpu != requester_vcpu && /* Current thread is not the VCPU thread */