[RFC PATCH 1/1] drm/amdgpu: add initial support for pci error handler

[Andrey Grodzovsky]

On 8/11/20 9:30 AM, Nirmoy Das wrote:
> This patch will ignore non-fatal errors and try to
> stop amdgpu's sw stack on fatal errors.
>
> Signed-off-by: Nirmoy Das <nirmoy.das at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 56 ++++++++++++++++++++++++-
>   1 file changed, 54 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index c1219af2e7d6..2b9ede3000ee 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -35,6 +35,7 @@
>   #include <linux/pm_runtime.h>
>   #include <linux/vga_switcheroo.h>
>   #include <drm/drm_probe_helper.h>
> +#include <drm/drm_atomic_helper.h>
>   #include <linux/mmu_notifier.h>
>   
>   #include "amdgpu.h"
> @@ -1516,6 +1517,58 @@ static struct drm_driver kms_driver = {
>   	.patchlevel = KMS_DRIVER_PATCHLEVEL,
>   };
>   
> +static pci_ers_result_t amdgpu_pci_err_detected(struct pci_dev *pdev,
> +						pci_channel_state_t state)
> +{
> +	struct drm_device *dev = pci_get_drvdata(pdev);
> +	struct amdgpu_device *adev = dev->dev_private;
> +	int i;
> +	int ret = PCI_ERS_RESULT_DISCONNECT;
> +
> +	switch (state) {
> +	case pci_channel_io_normal:
> +		ret = PCI_ERS_RESULT_CAN_RECOVER;
> +		break;
> +	default:
> +		/* Disable power management */
> +		adev->runpm = 0;
> +		/* Suspend all IO operations */
> +		amdgpu_fbdev_set_suspend(adev, 1);
> +		cancel_delayed_work_sync(&adev->delayed_init_work);
> +		for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
> +			struct amdgpu_ring *ring = adev->rings[i];
> +
> +			if (!ring || !ring->sched.thread)
> +				continue;
> +
> +			amdgpu_job_stop_all_jobs_on_sched(&ring->sched);


You need to call drm_sched_stop first before calling this

> +		}
> +
> +		if (adev->mode_info.mode_config_initialized) {
> +			if (!amdgpu_device_has_dc_support(adev))
> +				drm_helper_force_disable_all(adev->ddev);
> +			else
> +				drm_atomic_helper_shutdown(adev->ddev);
> +		}
> +
> +		amdgpu_fence_driver_fini(adev);
> +		amdgpu_fbdev_fini(adev);
> +		/* Try to close drm device to stop applications
> +		 * from opening dri files for further IO operations.
> +		 * TODO: This will throw warning as ttm is not
> +		 * cleaned perperly */
> +		drm_dev_fini(dev);


I think user mode applications might still hold reference to the drm device 
through through drm_dev_get either by directly opening
the device file or indirectly through importing DMA buff, if so when the last of 
them terminate drm_dev_put->drm_dev_release->...->drm_dev_fini
might get called again causing use after free e.t.c issues. Maybe better to call 
here drm_dev_put then and so drm_dev_fini will get called when this
last user client releases his reference.

Also a general question - in my work on DPC recovery feature which tries to 
recover after PCIe error - once the PCI error has happened MMIO registers become
unaccessible for r/w as the PCI link is dead until after the PCI link is reset 
by the DPC driver (see 
https://www.kernel.org/doc/html/latest/PCI/pci-error-recovery.html section 6.1.4).
Your case is to try and gracefully to close the drm device once fatal error 
happened, didn't you encounter errors or warnings when accessing HW registers 
during any of the operations
above ?

Andrey


> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static const struct pci_error_handlers amdgpu_err_handler = {
> +       .error_detected = amdgpu_pci_err_detected,
> +};
> +
> +
>   static struct pci_driver amdgpu_kms_pci_driver = {
>   	.name = DRIVER_NAME,
>   	.id_table = pciidlist,
> @@ -1523,10 +1576,9 @@ static struct pci_driver amdgpu_kms_pci_driver = {
>   	.remove = amdgpu_pci_remove,
>   	.shutdown = amdgpu_pci_shutdown,
>   	.driver.pm = &amdgpu_pm_ops,
> +	.err_handler = &amdgpu_err_handler,
>   };
>   
> -
> -
>   static int __init amdgpu_init(void)
>   {
>   	int r;