On 4/8/24 15:56, Nilay Shroff wrote:
> If the nvme subsyetm reset causes the loss of communication to the nvme
> adapter then EEH could potnetially recover the adapter. The detection of
> comminication loss to the adapter only happens when the nvme driver
> attempts to read an MMIO register.
>
> The nvme subsystem reset command writes 0x4E564D65 to NSSR register and
> schedule adapter reset.In the case nvme subsystem reset caused the loss
> of communication to the nvme adapter then either IO timeout event or
> adapter reset handler could detect it. If IO timeout event could detect
> loss of communication then EEH handler is able to recover the communication
> to the adapter. This change was implemented in commit 651438bb0af5
> ("nvme-pci: Fix EEH failure on ppc"). However if the adapter communication
> loss is detected during nvme reset work then EEH is unable to successfully
> finish the adapter recovery.
>
> This patch ensures that,
> - nvme reset work can observer pci channel is offline (at-least on the
> paltfrom which supports EEH recovery) after a failed MMIO read and
> contains reset work forward progress and marking controller state to
> DEAD. Thus we give a fair chance to EEH handler to recover the nvme
> adapter.
>
> - if pci channel "frozen" error is detected while controller is already
> in the RESETTING state then don't try (re-)setting controller state to
> RESETTING which would otherwise obviously fail and we may prematurely
> breaks out of the EEH recovery handling.
>
> - if pci channel "frozen" error is detected while reset work is in progress
> then wait until reset work is finished before proceeding with nvme dev
> disable. This would ensure that the reset work doesn't race with the
> pci error handler code and both error handler and reset work forward
> progress without blocking.
>
> Signed-off-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
> ---
> Changes from v1:
> - Allow a controller to reset from a connecting state (Keith)
>
> - Fix race condition between reset work and pci error handler
> code which may contain reset work and EEH recovery from
> forward progress (Keith)
>
> drivers/nvme/host/core.c | 1 +
> drivers/nvme/host/pci.c | 19 ++++++++++++++++---
> 2 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 27281a9a8951..b3fe1a02c171 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -557,6 +557,7 @@ bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
> switch (old_state) {
> case NVME_CTRL_NEW:
> case NVME_CTRL_LIVE:
> + case NVME_CTRL_CONNECTING:
> changed = true;
> fallthrough;
> default:
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index 8e0bb9692685..553bf0ec5f5c 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -2776,6 +2776,16 @@ static void nvme_reset_work(struct work_struct *work)
> out_unlock:
> mutex_unlock(&dev->shutdown_lock);
> out:
> + /*
> + * If PCI recovery is ongoing then let it finish first
> + */
> + if (pci_channel_offline(to_pci_dev(dev->dev))) {
> + if (nvme_ctrl_state(&dev->ctrl) == NVME_CTRL_RESETTING ||
> + nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING)) {
> + dev_warn(dev->ctrl.device, "Let pci error recovery finish!\n");
> + return;
> + }
> + }
> /*
> * Set state to deleting now to avoid blocking nvme_wait_reset(), which
> * may be holding this pci_dev's device lock.
> @@ -3295,10 +3305,13 @@ static pci_ers_result_t nvme_error_detected(struct pci_dev *pdev,
> case pci_channel_io_frozen:
> dev_warn(dev->ctrl.device,
> "frozen state error detected, reset controller\n");
> - if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING)) {
> - nvme_dev_disable(dev, true);
> - return PCI_ERS_RESULT_DISCONNECT;
> + if (nvme_ctrl_state(&dev->ctrl) != NVME_CTRL_RESETTING) {
> + if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING)) {
> + nvme_dev_disable(dev, true);
> + return PCI_ERS_RESULT_DISCONNECT;
> + }
> }
> + flush_work(&dev->ctrl.reset_work);
> nvme_dev_disable(dev, false);
> return PCI_ERS_RESULT_NEED_RESET;
> case pci_channel_io_perm_failure:
A gentle ping... Can I get some feedback?
For reference, link to first version of the patch is here: https://lore.kernel.org/all/20240209050342.406184-1-nilay@xxxxxxxxxxxxx/
Thanks,
--Nilay
