Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751353AbdH3Kmw (ORCPT ); Wed, 30 Aug 2017 06:42:52 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:42584 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751186AbdH3Kmv (ORCPT ); Wed, 30 Aug 2017 06:42:51 -0400 Subject: Re: [PATCH v3 41/59] KVM: arm/arm64: GICv4: Wire mapping/unmapping of VLPIs in VFIO irq bypass To: Auger Eric , Christoffer Dall Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Christoffer Dall , Thomas Gleixner , Jason Cooper , Shanker Donthineni , Mark Rutland , Shameerali Kolothum Thodi References: <20170731172637.29355-1-marc.zyngier@arm.com> <20170731172637.29355-42-marc.zyngier@arm.com> <20170826194850.GB11074@cbox> <53116ae6-fd94-2687-740f-5917e158eda7@arm.com> From: Marc Zyngier Organization: ARM Ltd Message-ID: <6c6aad59-8e36-dc7e-1aef-8f95de7d7eef@arm.com> Date: Wed, 30 Aug 2017 11:42:46 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6467 Lines: 179 Hi Eric, On 30/08/17 11:20, Auger Eric wrote: > Hi Marc, > > On 30/08/2017 11:42, Marc Zyngier wrote: >> On 26/08/17 20:48, Christoffer Dall wrote: >>> On Mon, Jul 31, 2017 at 06:26:19PM +0100, Marc Zyngier wrote: >>>> Let's use the irq bypass mechanism introduced for platform device >>>> interrupts to intercept the virtual PCIe endpoint configuration >>>> and establish our LPI->VLPI mapping. >>>> >>>> Signed-off-by: Marc Zyngier >>>> --- >>>> include/kvm/arm_vgic.h | 8 ++++ >>>> virt/kvm/arm/arm.c | 27 ++++++++---- >>>> virt/kvm/arm/vgic/vgic-v4.c | 103 ++++++++++++++++++++++++++++++++++++++++++++ >>>> 3 files changed, 130 insertions(+), 8 deletions(-) >>>> >>>> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h >>>> index 359eeffe9857..050f78d4fb42 100644 >>>> --- a/include/kvm/arm_vgic.h >>>> +++ b/include/kvm/arm_vgic.h >>>> @@ -367,4 +367,12 @@ int kvm_vgic_set_forwarding(struct kvm *kvm, unsigned int host_irq, >>>> void kvm_vgic_unset_forwarding(struct kvm *kvm, unsigned int host_irq, >>>> unsigned int vintid); >>>> >>>> +struct kvm_kernel_irq_routing_entry; >>>> + >>>> +int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int irq, >>>> + struct kvm_kernel_irq_routing_entry *irq_entry); >>>> + >>>> +int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int irq, >>>> + struct kvm_kernel_irq_routing_entry *irq_entry); >>>> + >>>> #endif /* __KVM_ARM_VGIC_H */ >>>> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c >>>> index ebab6c29e3be..6803ea27c47d 100644 >>>> --- a/virt/kvm/arm/arm.c >>>> +++ b/virt/kvm/arm/arm.c >>>> @@ -1457,11 +1457,16 @@ int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *cons, >>>> struct kvm_kernel_irqfd *irqfd = >>>> container_of(cons, struct kvm_kernel_irqfd, consumer); >>>> >>>> - if (prod->type != IRQ_BYPASS_VFIO_PLATFORM) >>>> + switch (prod->type) { >>>> + case IRQ_BYPASS_VFIO_PLATFORM: >>>> + return kvm_vgic_set_forwarding(irqfd->kvm, prod->irq, >>>> + irqfd->gsi + VGIC_NR_PRIVATE_IRQS); >>>> + case IRQ_BYPASS_VFIO_PCI_MSI: >>>> + return kvm_vgic_v4_set_forwarding(irqfd->kvm, prod->irq, >>>> + &irqfd->irq_entry); >>>> + default: >>>> return 0; >>>> - >>>> - return kvm_vgic_set_forwarding(irqfd->kvm, prod->irq, >>>> - irqfd->gsi + VGIC_NR_PRIVATE_IRQS); >>>> + } >>>> } >>>> void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons, >>>> struct irq_bypass_producer *prod) >>>> @@ -1469,11 +1474,17 @@ void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons, >>>> struct kvm_kernel_irqfd *irqfd = >>>> container_of(cons, struct kvm_kernel_irqfd, consumer); >>>> >>>> - if (prod->type != IRQ_BYPASS_VFIO_PLATFORM) >>>> - return; >>>> + switch (prod->type) { >>>> + case IRQ_BYPASS_VFIO_PLATFORM: >>>> + kvm_vgic_unset_forwarding(irqfd->kvm, prod->irq, >>>> + irqfd->gsi + VGIC_NR_PRIVATE_IRQS); >>>> + break; >>>> >>>> - kvm_vgic_unset_forwarding(irqfd->kvm, prod->irq, >>>> - irqfd->gsi + VGIC_NR_PRIVATE_IRQS); >>>> + case IRQ_BYPASS_VFIO_PCI_MSI: >>>> + kvm_vgic_v4_unset_forwarding(irqfd->kvm, prod->irq, >>>> + &irqfd->irq_entry); >>>> + break; >>>> + } >>>> } >>>> >>>> void kvm_arch_irq_bypass_stop(struct irq_bypass_consumer *cons) >>>> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c >>>> index 207e1fda0dcd..338c86c5159f 100644 >>>> --- a/virt/kvm/arm/vgic/vgic-v4.c >>>> +++ b/virt/kvm/arm/vgic/vgic-v4.c >>>> @@ -72,3 +72,106 @@ void vgic_v4_teardown(struct kvm *kvm) >>>> its_vm->nr_vpes = 0; >>>> its_vm->vpes = NULL; >>>> } >>>> + >>>> +static struct vgic_its *vgic_get_its(struct kvm *kvm, >>>> + struct kvm_kernel_irq_routing_entry *irq_entry) >>>> +{ >>>> + struct kvm_msi msi = (struct kvm_msi) { >>>> + .address_lo = irq_entry->msi.address_lo, >>>> + .address_hi = irq_entry->msi.address_hi, >>>> + .data = irq_entry->msi.data, >>>> + .flags = irq_entry->msi.flags, >>>> + .devid = irq_entry->msi.devid, >>>> + }; >>>> + >>>> + /* >>>> + * Get a reference on the LPI. If NULL, this is not a valid >>>> + * translation for any of our vITSs. >>>> + */ >>>> + return vgic_msi_to_its(kvm, &msi); >>>> +} >>>> + >>>> +int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq, >>>> + struct kvm_kernel_irq_routing_entry *irq_entry) >>>> +{ >>>> + struct vgic_its *its; >>>> + struct vgic_irq *irq; >>>> + struct its_vlpi_map map; >>>> + int ret; >>>> + >>>> + if (!vgic_is_v4_capable(kvm)) >>>> + return 0; >>>> + >>>> + /* >>>> + * Get the ITS, and escape early on error (not a valid >>>> + * doorbell for any of our vITSs). >>>> + */ >>>> + its = vgic_get_its(kvm, irq_entry); >>>> + if (IS_ERR(its)) >>>> + return 0; >>>> + >>>> + mutex_lock(&its->its_lock); >>>> + >>>> + /* Perform then actual DevID/EventID -> LPI translation. */ >>>> + ret = vgic_its_resolve_lpi(kvm, its, irq_entry->msi.devid, >>>> + irq_entry->msi.data, &irq); >>>> + if (ret) >>>> + goto out; >>>> + >>>> + /* >>>> + * Emit the mapping request. If it fails, the ITS probably >>>> + * isn't v4 compatible, so let's silently bail out. Holding >>>> + * the ITS lock should ensure that nothing can modify the >>>> + * target vcpu. >>>> + */ >>>> + map = (struct its_vlpi_map) { >>>> + .vm = &kvm->arch.vgic.its_vm, >>>> + .vintid = irq->intid, >>>> + .db_enabled = true, >>>> + .vpe_idx = irq->target_vcpu->vcpu_id, >>>> + }; >>>> + >>>> + if (its_map_vlpi(virq, &map)) >>>> + goto out; >>> >>> This seems to be able to return things like -ENOMEM, whould we really >>> not report this back to the caller in any way? >> >> >> That's a good question. >> >> If we return -ENOMEM, we'll probably end-up returning an error to >> userspace (as a result of the VFIO ioctl), which will in turn probably >> terminate the guest (I'm guessing, I haven't actually looked at what >> userspace does). >> >> If we don't return the error, then we have a chance to keep the guest >> running by sticking to software injection. > I have not read the whole stuff yet but userspace is not aware of this > negotiation. Everything happens under the hood in kernel, see > virt/lib/irqbypass.c __connect(): if add_producer() fails > prod->del_consumer() is called and we should return to the not optimized > injection. Ah, fair enough. I guess del_consumer() does nothing on PCI? Thanks, M. -- Jazz is not dead. It just smells funny...