Messages in this thread Patch in this message | | | From | Ben Luo <> | Subject | [PATCH v4 3/3] vfio/pci: make use of irq_update_devid and optimize irq ops | Date | Thu, 22 Aug 2019 23:34:43 +0800 |
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When userspace (e.g. qemu) triggers a switch between KVM irqfd and userspace eventfd, only dev_id of irq action (i.e. the "trigger" in this patch's context) will be changed, but a free-then-request-irq action is taken in current code. And, irq affinity setting in VM will also trigger a free-then-request-irq action, which actually changes nothing, but only fires a producer re-registration to update irte in case that posted-interrupt is in use.
This patch makes use of irq_update_devid() and optimize both cases above, which reduces the risk of losing interrupt and also cuts some overhead.
Signed-off-by: Ben Luo <luoben@linux.alibaba.com> --- drivers/vfio/pci/vfio_pci_intrs.c | 112 +++++++++++++++++++++++++------------- 1 file changed, 74 insertions(+), 38 deletions(-)
diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c index 3fa3f72..60d3023 100644 --- a/drivers/vfio/pci/vfio_pci_intrs.c +++ b/drivers/vfio/pci/vfio_pci_intrs.c @@ -284,70 +284,106 @@ static int vfio_msi_enable(struct vfio_pci_device *vdev, int nvec, bool msix) static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev, int vector, int fd, bool msix) { + struct eventfd_ctx *trigger = NULL; struct pci_dev *pdev = vdev->pdev; - struct eventfd_ctx *trigger; int irq, ret; if (vector < 0 || vector >= vdev->num_ctx) return -EINVAL; + if (fd >= 0) { + trigger = eventfd_ctx_fdget(fd); + if (IS_ERR(trigger)) + return PTR_ERR(trigger); + } + irq = pci_irq_vector(pdev, vector); + /* + * For KVM-VFIO case, interrupt from passthrough device will be directly + * delivered to VM after producer and consumer connected successfully. + * If producer and consumer are disconnected, this interrupt process + * will fall back to remap mode, where interrupt handler uses 'trigger' + * to find the right way to deliver the interrupt to VM. So, it is safe + * to do irq_update_devid() before irq_bypass_unregister_producer() which + * switches interrupt process to remap mode. To producer and consumer, + * 'trigger' is only a token used for pairing them togather. + */ if (vdev->ctx[vector].trigger) { - free_irq(irq, vdev->ctx[vector].trigger); - irq_bypass_unregister_producer(&vdev->ctx[vector].producer); - kfree(vdev->ctx[vector].name); - eventfd_ctx_put(vdev->ctx[vector].trigger); - vdev->ctx[vector].trigger = NULL; + if (vdev->ctx[vector].trigger == trigger) { + /* switch back to remap mode */ + irq_bypass_unregister_producer(&vdev->ctx[vector].producer); + } else if (trigger) { + ret = irq_update_devid(irq, + vdev->ctx[vector].trigger, trigger); + if (unlikely(ret)) { + dev_info(&pdev->dev, + "update devid of %d (token %p) failed: %d\n", + irq, vdev->ctx[vector].trigger, ret); + eventfd_ctx_put(trigger); + return ret; + } + irq_bypass_unregister_producer(&vdev->ctx[vector].producer); + eventfd_ctx_put(vdev->ctx[vector].trigger); + vdev->ctx[vector].producer.token = trigger; + vdev->ctx[vector].trigger = trigger; + } else { + free_irq(irq, vdev->ctx[vector].trigger); + irq_bypass_unregister_producer(&vdev->ctx[vector].producer); + kfree(vdev->ctx[vector].name); + eventfd_ctx_put(vdev->ctx[vector].trigger); + vdev->ctx[vector].trigger = NULL; + } } if (fd < 0) return 0; - vdev->ctx[vector].name = kasprintf(GFP_KERNEL, "vfio-msi%s[%d](%s)", - msix ? "x" : "", vector, - pci_name(pdev)); - if (!vdev->ctx[vector].name) - return -ENOMEM; + if (!vdev->ctx[vector].trigger) { + vdev->ctx[vector].name = kasprintf(GFP_KERNEL, + "vfio-msi%s[%d](%s)", + msix ? "x" : "", vector, + pci_name(pdev)); + if (!vdev->ctx[vector].name) { + eventfd_ctx_put(trigger); + return -ENOMEM; + } - trigger = eventfd_ctx_fdget(fd); - if (IS_ERR(trigger)) { - kfree(vdev->ctx[vector].name); - return PTR_ERR(trigger); - } + /* + * The MSIx vector table resides in device memory which may be + * cleared via backdoor resets. We don't allow direct access to + * the vector table so even if a userspace driver attempts to + * save/restore around such a reset it would be unsuccessful. + * To avoid this, restore the cached value of the message prior + * to enabling. + */ + if (msix) { + struct msi_msg msg; - /* - * The MSIx vector table resides in device memory which may be cleared - * via backdoor resets. We don't allow direct access to the vector - * table so even if a userspace driver attempts to save/restore around - * such a reset it would be unsuccessful. To avoid this, restore the - * cached value of the message prior to enabling. - */ - if (msix) { - struct msi_msg msg; + get_cached_msi_msg(irq, &msg); + pci_write_msi_msg(irq, &msg); + } - get_cached_msi_msg(irq, &msg); - pci_write_msi_msg(irq, &msg); - } + ret = request_irq(irq, vfio_msihandler, 0, + vdev->ctx[vector].name, trigger); + if (ret) { + kfree(vdev->ctx[vector].name); + eventfd_ctx_put(trigger); + return ret; + } - ret = request_irq(irq, vfio_msihandler, 0, - vdev->ctx[vector].name, trigger); - if (ret) { - kfree(vdev->ctx[vector].name); - eventfd_ctx_put(trigger); - return ret; + vdev->ctx[vector].producer.token = trigger; + vdev->ctx[vector].producer.irq = irq; + vdev->ctx[vector].trigger = trigger; } - vdev->ctx[vector].producer.token = trigger; - vdev->ctx[vector].producer.irq = irq; + /* setup bypass connection and make irte updated */ ret = irq_bypass_register_producer(&vdev->ctx[vector].producer); if (unlikely(ret)) dev_info(&pdev->dev, "irq bypass producer (token %p) registration fails: %d\n", vdev->ctx[vector].producer.token, ret); - vdev->ctx[vector].trigger = trigger; - return 0; } -- 1.8.3.1
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