Re: [PATCH] drm/amdgpu: use IRQ-safe xarray API for PASID management

["Christian König" <christian.koenig@amd.com>]

On 4/1/26 09:36, Mikhail Gavrilov wrote:
> xa_alloc_cyclic() and xa_erase() use plain xa_lock()/xa_unlock()
> regardless of XA_FLAGS_LOCK_IRQ — the flag only affects lockdep
> annotations, not runtime locking.
> 
> Switch to xa_alloc_cyclic_irq() and xa_erase_irq() which use
> xa_lock_irq/xa_unlock_irq internally, fixing the IRQ safety issue
> for amdgpu_pasid_free() called from hardirq via fence callbacks.
> 
> Fixes: a3c0ee978e16 ("drm/amdgpu: replace PASID IDR with XArray")
> Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> index a6ac3b4ce0df..64d0da28441f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> @@ -68,7 +68,7 @@ int amdgpu_pasid_alloc(unsigned int bits)
>  	if (bits == 0)
>  		return -EINVAL;
>  
> -	r = xa_alloc_cyclic(&amdgpu_pasid_xa, &pasid, xa_mk_value(0),
> +	r = xa_alloc_cyclic_irq(&amdgpu_pasid_xa, &pasid, xa_mk_value(0),
>  			    XA_LIMIT(1, (1U << bits) - 1),
>  			    &amdgpu_pasid_xa_next, GFP_KERNEL);
>  	if (r < 0)
> @@ -85,7 +85,7 @@ int amdgpu_pasid_alloc(unsigned int bits)
>  void amdgpu_pasid_free(u32 pasid)
>  {
>  	trace_amdgpu_pasid_freed(pasid);
> -	xa_erase(&amdgpu_pasid_xa, pasid);
> +	xa_erase_irq(&amdgpu_pasid_xa, pasid);

This one needs to use:

xa_lock_irqsave(xa, flags);
__xa_eras(...);
xa_unlock_irqrestore(xa, flags);

Since it is actually used in IRQ context and not process context.

Apart from that looks good to me.

Regards,
Christian.


>  }
>  
>  static void amdgpu_pasid_free_cb(struct dma_fence *fence,