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Date: Mon, 27 Feb 2017 18:16:57 +0200
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Cao jin <caoj.fnst@...fujitsu.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
qemu-devel@...gnu.org, alex.williamson@...hat.com,
izumi.taku@...fujitsu.com
Subject: Re: [PATCH] vfio pci: kernel support of error recovery only for non
fatal error
On Mon, Feb 27, 2017 at 03:28:43PM +0800, Cao jin wrote:
> Subject: Re: [PATCH] vfio pci: kernel support of error recovery only for non
> fatal error
Don't make the subject so long. This is why I had
[PATCH v3] vfio error recovery: kernel support
you also want to add versioning as you inherited my v3,
you should make this v4 etc.
> 0. What happens now (PCIE AER only)
> Fatal errors cause a link reset.
> Non fatal errors don't.
> All errors stop the VM eventually, but not immediately
> because it's detected and reported asynchronously.
> Interrupts are forwarded as usual.
> Correctable errors are not reported to guest at all.
> Note: PPC EEH is different. This focuses on AER.
>
> 1. Correctable errors
> There is no need to report these to guest. So let's not.
>
> 2. Fatal errors
> It's not easy to handle them gracefully since link reset
> is needed. As a first step, let's use the existing mechanism
> in that case.
>
> 2. Non-fatal errors
> Here we could make progress by reporting them to guest
> and have guest handle them.
>
> Issues:
> a. this behaviour should only be enabled with new userspace,
> old userspace should work without changes.
>
> Suggestion: One way to address this would be to add a new eventfd
> non_fatal_err_trigger. If not set, invoke err_trigger.
>
> b. drivers are supposed to stop MMIO when error is reported,
> if vm keeps going, we will keep doing MMIO/config.
>
> Suggestion 1: ignore this. vm stop happens much later when
> userspace runs anyway, so we are not making things much worse.
>
> Suggestion 2: try to stop MMIO/config, resume on resume call
>
> Patch below implements Suggestion 1.
>
> Note that although this is really against the documentation, which
> states error_detected() is the point at which the driver should quiesce
> the device and not touch it further (until diagnostic poking at
> mmio_enabled or full access at resume callback).
>
> Fixing this won't be easy. However, this is not a regression.
>
> Also note this does nothing about interrupts, documentation
> suggests returning IRQ_NONE until reset.
> Again, not a regression.
>
> c. PF driver might detect that function is completely broken,
> if vm keeps going, we will keep doing MMIO/config.
>
> Suggestion 1: ignore this. vm stop happens much later when
> userspace runs anyway, so we are not making things much worse.
>
> Suggestion 2: detect this and invoke err_trigger to stop VM.
>
> Patch below implements Suggestion 2.
>
> Suggested-by: Michael S. Tsirkin <mst@...hat.com>
It's more than this, you are really reusing parts of my patch,
so you should say so and include my signature.
If you only added a line or two you can keep
the original author. To do this you add
From: Michael S. Tsirkin <mst@...hat.com>
before commit text.
> Signed-off-by: Cao jin <caoj.fnst@...fujitsu.com>
> ---
Changelog from my v3?
> drivers/vfio/pci/vfio_pci.c | 38 +++++++++++++++++++++++++++++++++++--
> drivers/vfio/pci/vfio_pci_intrs.c | 19 +++++++++++++++++++
> drivers/vfio/pci/vfio_pci_private.h | 1 +
> include/uapi/linux/vfio.h | 1 +
> 4 files changed, 57 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index 324c52e..3551cc9 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -441,7 +441,8 @@ static int vfio_pci_get_irq_count(struct vfio_pci_device *vdev, int irq_type)
>
> return (flags & PCI_MSIX_FLAGS_QSIZE) + 1;
> }
> - } else if (irq_type == VFIO_PCI_ERR_IRQ_INDEX) {
> + } else if (irq_type == VFIO_PCI_ERR_IRQ_INDEX ||
> + irq_type == VFIO_PCI_NON_FATAL_ERR_IRQ_INDEX) {
> if (pci_is_pcie(vdev->pdev))
> return 1;
> } else if (irq_type == VFIO_PCI_REQ_IRQ_INDEX) {
> @@ -796,6 +797,7 @@ static long vfio_pci_ioctl(void *device_data,
> case VFIO_PCI_REQ_IRQ_INDEX:
> break;
> case VFIO_PCI_ERR_IRQ_INDEX:
> + case VFIO_PCI_NON_FATAL_ERR_IRQ_INDEX:
> if (pci_is_pcie(vdev->pdev))
> break;
> /* pass thru to return error */
> @@ -1282,7 +1284,9 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
>
> mutex_lock(&vdev->igate);
>
> - if (vdev->err_trigger)
> + if (state == pci_channel_io_normal && vdev->non_fatal_err_trigger)
> + eventfd_signal(vdev->non_fatal_err_trigger, 1);
> + else if (vdev->err_trigger)
> eventfd_signal(vdev->err_trigger, 1);
>
> mutex_unlock(&vdev->igate);
> @@ -1292,8 +1296,38 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
> return PCI_ERS_RESULT_CAN_RECOVER;
> }
>
> +static pci_ers_result_t vfio_pci_aer_slot_reset(struct pci_dev *pdev)
> +{
> + struct vfio_pci_device *vdev;
> + struct vfio_device *device;
> + static pci_ers_result_t err = PCI_ERS_RESULT_NONE;
> +
> + device = vfio_device_get_from_dev(&pdev->dev);
> + if (!device)
> + goto err_dev;
> +
> + vdev = vfio_device_data(device);
> + if (!vdev)
> + goto err_data;
> +
> + mutex_lock(&vdev->igate);
> +
> + if (vdev->err_trigger)
> + eventfd_signal(vdev->err_trigger, 1);
> +
> + mutex_unlock(&vdev->igate);
> +
> + err = PCI_ERS_RESULT_RECOVERED;
> +
> +err_data:
> + vfio_device_put(device);
> +err_dev:
> + return err;
> +}
> +
> static const struct pci_error_handlers vfio_err_handlers = {
> .error_detected = vfio_pci_aer_err_detected,
> + .slot_reset = vfio_pci_aer_slot_reset,
> };
>
> static struct pci_driver vfio_pci_driver = {
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 1c46045..270d568 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -611,6 +611,17 @@ static int vfio_pci_set_err_trigger(struct vfio_pci_device *vdev,
> count, flags, data);
> }
>
> +static int vfio_pci_set_non_fatal_err_trigger(struct vfio_pci_device *vdev,
> + unsigned index, unsigned start,
> + unsigned count, uint32_t flags, void *data)
> +{
> + if (index != VFIO_PCI_NON_FATAL_ERR_IRQ_INDEX || start != 0 || count > 1)
> + return -EINVAL;
> +
> + return vfio_pci_set_ctx_trigger_single(&vdev->non_fatal_err_trigger,
> + count, flags, data);
> +}
> +
> static int vfio_pci_set_req_trigger(struct vfio_pci_device *vdev,
> unsigned index, unsigned start,
> unsigned count, uint32_t flags, void *data)
> @@ -664,6 +675,14 @@ int vfio_pci_set_irqs_ioctl(struct vfio_pci_device *vdev, uint32_t flags,
> break;
> }
> break;
> + case VFIO_PCI_NON_FATAL_ERR_IRQ_INDEX:
> + switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
> + case VFIO_IRQ_SET_ACTION_TRIGGER:
> + if (pci_is_pcie(vdev->pdev))
> + func = vfio_pci_set_non_fatal_err_trigger;
> + break;
> + }
> + break;
> case VFIO_PCI_REQ_IRQ_INDEX:
> switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
> case VFIO_IRQ_SET_ACTION_TRIGGER:
> diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
> index f561ac1..d30f8a3 100644
> --- a/drivers/vfio/pci/vfio_pci_private.h
> +++ b/drivers/vfio/pci/vfio_pci_private.h
> @@ -93,6 +93,7 @@ struct vfio_pci_device {
> struct pci_saved_state *pci_saved_state;
> int refcnt;
> struct eventfd_ctx *err_trigger;
> + struct eventfd_ctx *non_fatal_err_trigger;
> struct eventfd_ctx *req_trigger;
> struct list_head dummy_resources_list;
> };
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 519eff3..affa973 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -443,6 +443,7 @@ enum {
> VFIO_PCI_MSIX_IRQ_INDEX,
> VFIO_PCI_ERR_IRQ_INDEX,
> VFIO_PCI_REQ_IRQ_INDEX,
> + VFIO_PCI_NON_FATAL_ERR_IRQ_INDEX,
> VFIO_PCI_NUM_IRQS
> };
>
> --
> 1.8.3.1
>
>
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