[PATCH] drm/amdgpu: Update SPM_VMID with the job's vmid when application reserves the vmid

[He, Jacob]

[AMD Official Use Only - Internal Distribution Only]

Thanks!  Could you please take an example of trouble  “This way we avoid a bunch of trouble when one process drops the VMID reservation and another one grabs it.”?

Thanks
Jacob

From: Koenig, Christian<mailto:Christian.Koenig at amd.com>
Sent: Tuesday, March 3, 2020 11:03 PM
To: He, Jacob<mailto:Jacob.He at amd.com>; amd-gfx at lists.freedesktop.org<mailto:amd-gfx at lists.freedesktop.org>
Subject: Re: [PATCH] drm/amdgpu: Update SPM_VMID with the job's vmid when application reserves the vmid

Am 03.03.20 um 15:34 schrieb He, Jacob:

[AMD Official Use Only - Internal Distribution Only]

It would be better if we could do that asynchronously with a register
write on the ring.
Sorry, I don’t get your point. Could you please elaborate more?

You pass the ring from amdgpu_vm_flush() to the *_update_spm_vmid() functions.

And then instead of using WREG32() you call amdgpu_ring_emit_wreg() to make the write asynchronously on the ring buffer using a CP command.

This way we avoid a bunch of trouble when one process drops the VMID reservation and another one grabs it.

Regards,
Christian.



Thanks
Jacob

From: Christian König<mailto:ckoenig.leichtzumerken at gmail.com>
Sent: Tuesday, March 3, 2020 10:16 PM
To: He, Jacob<mailto:Jacob.He at amd.com>; amd-gfx at lists.freedesktop.org<mailto:amd-gfx at lists.freedesktop.org>
Subject: Re: [PATCH] drm/amdgpu: Update SPM_VMID with the job's vmid when application reserves the vmid

Am 02.03.20 um 06:35 schrieb Jacob He:
> SPM access the video memory according to SPM_VMID. It should be updated
> with the job's vmid right before the job is scheduled. SPM_VMID is a
> global resource
>
> Change-Id: Id3881908960398f87e7c95026a54ff83ff826700
> Signed-off-by: Jacob He <jacob.he at amd.com><mailto:jacob.he at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index c00696f3017e..c761d3a0b6e8 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -1080,8 +1080,12 @@ int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job,
>        struct dma_fence *fence = NULL;
>        bool pasid_mapping_needed = false;
>        unsigned patch_offset = 0;
> +     bool update_spm_vmid_needed = (job->vm && (job->vm->reserved_vmid[vmhub] != NULL));
>        int r;
>
> +     if (update_spm_vmid_needed && adev->gfx.rlc.funcs->update_spm_vmid)
> +             adev->gfx.rlc.funcs->update_spm_vmid(adev, job->vmid);
> +

It would be better if we could do that asynchronously with a register
write on the ring.

The alternative is that we block for the VM to be idle in
amdgpu_vm_ioctl() before unreserving the VMID.

In other words lock the reservation object of the root PD and call
amdgpu_vm_wait_idle() before calling amdgpu_vmid_free_reserved().

Regards,
Christian.

>        if (amdgpu_vmid_had_gpu_reset(adev, id)) {
>                gds_switch_needed = true;
>                vm_flush_needed = true;



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