Re: [RFC PATCH v1 1/8] drm/amdkfd: Relax size checking during queue buffer get

[Donet Tom <donettom@linux.ibm.com>]

On 12/16/25 1:55 AM, Philip Yang wrote:
>
>
> On 2025-12-12 01:40, Donet Tom wrote:
>> HW-supported EOP buffer sizes are 4K and 32K. On systems that do not
>> use 4K pages, the minimum buffer object (BO) allocation size is
>> PAGE_SIZE (for example, 64K). During queue buffer acquisition, the 
>> driver
>> currently checks the allocated BO size against the supported EOP buffer
>> size. Since the allocated BO is larger than the expected size, this 
>> check
>> fails, preventing queue creation.
>>
>> Relax the strict size validation and allow PAGE_SIZE-sized BOs to be 
>> used.
>> Only the required 4K region of the buffer will be used as the EOP buffer
>> and avoids queue creation failures on non-4K page systems.
>>
>> Signed-off-by: Donet Tom <donettom@linux.ibm.com>
>> ---
>>   drivers/gpu/drm/amd/amdkfd/kfd_queue.c | 10 ++++++----
>>   1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_queue.c 
>> b/drivers/gpu/drm/amd/amdkfd/kfd_queue.c
>> index f1e7583650c4..dc857450fa16 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_queue.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_queue.c
>> @@ -199,6 +199,7 @@ int kfd_queue_buffer_get(struct amdgpu_vm *vm, 
>> void __user *addr, struct amdgpu_
>>       struct amdgpu_bo_va_mapping *mapping;
>>       u64 user_addr;
>>       u64 size;
>> +    u64 bo_size;
>>         user_addr = (u64)addr >> AMDGPU_GPU_PAGE_SHIFT;
>>       size = expected_size >> AMDGPU_GPU_PAGE_SHIFT;
>> @@ -207,11 +208,12 @@ int kfd_queue_buffer_get(struct amdgpu_vm *vm, 
>> void __user *addr, struct amdgpu_
>>       if (!mapping)
>>           goto out_err;
>>   -    if (user_addr != mapping->start ||
>> -        (size != 0 && user_addr + size - 1 != mapping->last)) {
>> -        pr_debug("expected size 0x%llx not equal to mapping addr 
>> 0x%llx size 0x%llx\n",
>> +    bo_size = mapping->last - mapping->start + 1;
>> +
>> +    if (user_addr != mapping->start || (size != 0 && bo_size < size)) {
>> +        pr_debug("expected size 0x%llx grater than mapping addr 
>> 0x%llx size 0x%llx\n",
>>               expected_size, mapping->start << AMDGPU_GPU_PAGE_SHIFT,
>> -            (mapping->last - mapping->start + 1) << 
>> AMDGPU_GPU_PAGE_SHIFT);
>> +            bo_size <<  AMDGPU_GPU_PAGE_SHIFT);
> This change works, but also relax the size validation for ring buffer 
> size etc, this may have side effect,
> for example FW and user space should have the same ring buffer size.
>
> Other buffers already use PAGE_SIZE as expected size or size aligned 
> to PAGE_SIZE, maybe only relax the eop buffer
> size check
>
> @@ -275,7 +275,7 @@ int kfd_queue_acquire_buffers(struct 
> kfd_process_device *pdd, struct queue_prope
>
>         /* EOP buffer is not required for all ASICs */
>         if (properties->eop_ring_buffer_address) {
> -               if (properties->eop_ring_buffer_size != 
> topo_dev->node_props.eop_buffer_size) {
> +               if (properties->eop_ring_buffer_size < 
> topo_dev->node_props.eop_buffer_size) {
>                         pr_debug("queue eop bo size 0x%x not equal to 
> node eop buf size 0x%x\n",
> properties->eop_ring_buffer_size,
> topo_dev->node_props.eop_buffer_size);
> @@ -284,7 +284,7 @@ int kfd_queue_acquire_buffers(struct 
> kfd_process_device *pdd, struct queue_prope
>                 }
>                 err = kfd_queue_buffer_get(vm, (void 
> *)properties->eop_ring_buffer_address,
> &properties->eop_buf_bo,
> - properties->eop_ring_buffer_size);
> + ALIGN(properties->eop_ring_buffer_size, PAGE_SIZE));
>                 if (err)
>                         goto out_err_unreserve;
>         }


Thank you. I will make this change in next version.


>
> Regards,
> Philip
>>           goto out_err;
>>       }
>