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Date: Fri, 20 Jan 2017 18:13:22 +0800
From: Cao jin <caoj.fnst@...fujitsu.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
<qemu-devel@...gnu.org>, <izumi.taku@...fujitsu.com>,
<alex.williamson@...hat.com>
Subject: Re: [PATCH RFC] vfio error recovery: kernel support
On 01/20/2017 04:16 AM, Michael S. Tsirkin wrote:
> This is a design and an initial patch for kernel side for AER
> support in VFIO.
>
> 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
> I don't see a 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.
>
> 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.
>
> Aside: we currently return PCI_ERS_RESULT_DISCONNECT when device
> is not attached. This seems bogus, likely based on the confusing name.
> We probably should return PCI_ERS_RESULT_CAN_RECOVER.
>
> The following patch does not change that.
>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
>
> ---
>
> The patch is completely untested. Let's discuss the design first.
> Cao jin, if this is deemed acceptable please take it from here.
>
Ok, thanks very much.
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index dce511f..fdca683 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -1292,7 +1292,9 @@ 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->err_trigger, 1);
> + else if (vdev->err_trigger)
> eventfd_signal(vdev->err_trigger, 1);
>
> mutex_unlock(&vdev->igate);
> @@ -1302,8 +1304,38 @@ 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,
> + pci_channel_state_t state)
> +{
> + struct vfio_pci_device *vdev;
> + struct vfio_device *device;
> +
> + device = vfio_device_get_from_dev(&pdev->dev);
> + if (!device)
> + goto err_dev;
> +
> + vdev = vfio_device_data(device);
> + if (!vdev)
> + goto err_dev;
> +
> + mutex_lock(&vdev->igate);
> +
> + if (vdev->err_trigger)
> + eventfd_signal(vdev->err_trigger, 1);
> +
> + mutex_unlock(&vdev->igate);
> +
> + vfio_device_put(device);
> +
> +err_data:
> + vfio_device_put(device);
> +err_dev:
> + return PCI_ERS_RESULT_RECOVERED;
> +}
> +
> static const struct pci_error_handlers vfio_err_handlers = {
> .error_detected = vfio_pci_aer_err_detected,
> + .slot_reset = vfio_pci_aer_slot_reset,
> };
>
if .slot_reset wants to be called, .error_detected should return
PCI_ERS_RESULT_NEED_RESET, as pci-error-recovery.txt said, so does code.
Is .slot_reset now just a copy of .error_detected and we are going do
some tricks here? or else don't get why .slot_reset signal user again.
> 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..e883db5 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_err_trigger;
s/vfio_pci_set_err_trigger/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 f37c73b..c27a507 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;
> };
>
--
Sincerely,
Cao jin
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