Re: [PATCH] drm/amdgpu: fix userq page count in input_validate

["Zhu, Lingshan" <lingshan.zhu@amd.com>]

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On 7/17/2026 4:06 PM, Christian König wrote:

>
> On 7/17/26 04:25, Zhu Lingshan wrote:
>> amdgpu_userq_input_va_validate() converts userq
>> expected_size to page count by right shift.
>>
>> This undercounts va buffers that less than a page.
>> For example, in the AMDGPU_HW_IP_COMPUTE userq
>> creation case, the expected_size 2048,
>> so size(page count) becomes zero page and the
>> "va_map->last - user_addr + 1 >= size" is always true
>> once the start addr locates in the va_map mapping.
>>
>> A similar case is AMDGPU_HW_IP_DMA, where expected_size is 32.
>>
>> This commit calculates a proper page count by subtracting
>> the start_addr and end_addr in pages.
>>
>> Signed-off-by: Zhu Lingshan <lingshan.zhu@amd.com>
>> ---
>>  drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c | 14 +++++++++++---
>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
>> index 969f49592450..f9f11bdf2cef 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
>> @@ -25,6 +25,7 @@
>>  #include <drm/drm_auth.h>
>>  #include <drm/drm_exec.h>
>>  #include <linux/pm_runtime.h>
>> +#include <linux/overflow.h>
>>  #include <drm/drm_drv.h>
>>  
>>  #include "amdgpu.h"
>> @@ -238,14 +239,21 @@ int amdgpu_userq_input_va_validate(struct amdgpu_device *adev,
>>  {
>>  	struct amdgpu_bo_va_mapping *va_map;
>>  	struct amdgpu_vm *vm = queue->vm;
>> -	u64 user_addr;
>> +	u64 user_addr, end;
>>  	u64 size;
>>  
>>  	/* Caller must hold vm->root.bo reservation */
>>  	dma_resv_assert_held(queue->vm->root.bo->tbo.base.resv);
>>  
>> -	user_addr = (addr & AMDGPU_GMC_HOLE_MASK) >> AMDGPU_GPU_PAGE_SHIFT;
>> -	size = expected_size >> AMDGPU_GPU_PAGE_SHIFT;
> Good catch, but I would just use ALIGN(expected_size, AMDGPU_GPU_PAGE_SIZE) here.

Hello Christian

ALIGN is more concise, however it is only correct when start_addr is PAGE aligned.

It undercounts one page when start_addr is not page aligned and "start_addr + expected_size" crosses page boundary.

An example is, if start_addr is 0xC00 (1024 X 3), and expected_size is 2048, so the size should be two pages,
but the result of ALIGN() is one page, which is wrong. 

I think this "start - end" is a more general solution.

Thanks
Lingshan 

>
> Regards,
> Christian.
>
>> +	if (!expected_size)
>> +		return -EINVAL;
>> +
>> +	user_addr = addr & AMDGPU_GMC_HOLE_MASK;
>> +	if (check_add_overflow(user_addr, expected_size - 1, &end))
>> +		return -EINVAL;
>> +
>> +	user_addr >>= AMDGPU_GPU_PAGE_SHIFT;
>> +	size = (end >> AMDGPU_GPU_PAGE_SHIFT) - user_addr + 1;
>>  
>>  	va_map = amdgpu_vm_bo_lookup_mapping(vm, user_addr);
>>  	if (!va_map)

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