Re: [Intel-xe] [PATCH 3/4] drm/xe/vm: Perform accounting of userptr pinned pages

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On 8/20/23 05:43, Matthew Brost wrote:
> On Fri, Aug 18, 2023 at 05:08:44PM +0200, Thomas Hellström wrote:
>> Account these pages against RLIMIT_MEMLOCK following how RDMA does this
>> with CAP_IPC_LOCK bypassing the limit.
>>
>> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Patch LGTM but nits on naming + possible assert.
>
>> ---
>>   drivers/gpu/drm/xe/xe_vm.c | 43 ++++++++++++++++++++++++++++++++++++--
>>   1 file changed, 41 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
>> index ecbcad696b60..d9c000689002 100644
>> --- a/drivers/gpu/drm/xe/xe_vm.c
>> +++ b/drivers/gpu/drm/xe/xe_vm.c
>> @@ -34,6 +34,33 @@
>>   
>>   #define TEST_VM_ASYNC_OPS_ERROR
>>   
>> +/*
>> + * Perform userptr PIN accounting against RLIMIT_MEMLOCK for now, similarly
>> + * to how RDMA does this.
>> + */
>> +static int xe_vma_mlock_alloc(struct xe_vma *vma, unsigned long num_pages)
>> +{
> xe_vma_userptr_mlock_alloc? or maybe even xe_vma_userptr_mlock_reserve?
>
>> +	unsigned long lock_limit, new_pinned;
>> +	struct mm_struct *mm = vma->userptr.notifier.mm;
>> +
> This be a candidate to use the new aseert macros to ensure that the vma
> is a userptr + pinned? Not sure if that merged yet.
>
>> +	if (!can_do_mlock())
>> +		return -EPERM;
>> +
>> +	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>> +	new_pinned = atomic64_add_return(num_pages, &mm->pinned_vm);
>> +	if (new_pinned > lock_limit && !capable(CAP_IPC_LOCK)) {
>> +		atomic64_sub(num_pages, &mm->pinned_vm);
>> +		return -ENOMEM;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static void xe_vma_mlock_free(struct xe_vma *vma, unsigned long num_pages)
>> +{
> xe_vma_userptr_mlock_free? or maybe even xe_vma_userptr_mlock_release?
>
> Same for the assert here.
>
> Anyways, I'll leave addressing these nits up to you, with that:
> Reviewed-by: Matthew Brost <matthew.brost@intel.com>

OK, thanks. I'll take a look at addressing those.

>
>> +	atomic64_sub(num_pages, &vma->userptr.notifier.mm->pinned_vm);
>> +}
>> +
>>   /**
>>    * xe_vma_userptr_check_repin() - Advisory check for repin needed
>>    * @vma: The userptr vma
>> @@ -89,9 +116,17 @@ int xe_vma_userptr_pin_pages(struct xe_vma *vma)
>>   					    !read_only);
>>   		pages = vma->userptr.pinned_pages;
>>   	} else {
>> +		if (xe_vma_is_pinned(vma)) {
>> +			ret = xe_vma_mlock_alloc(vma, num_pages);
>> +			if (ret)
>> +				return ret;
>> +		}
>> +
>>   		pages = kvmalloc_array(num_pages, sizeof(*pages), GFP_KERNEL);
>> -		if (!pages)
>> -			return -ENOMEM;
>> +		if (!pages) {
>> +			ret = -ENOMEM;
>> +			goto out_account;
>> +		}
>>   	}
>>   
>>   	pinned = ret = 0;
>> @@ -187,6 +222,9 @@ int xe_vma_userptr_pin_pages(struct xe_vma *vma)
>>   mm_closed:
>>   	kvfree(pages);
>>   	vma->userptr.pinned_pages = NULL;
>> +out_account:
>> +	if (xe_vma_is_pinned(vma))
>> +		xe_vma_mlock_free(vma, num_pages);
>>   	return ret;
>>   }
>>   
>> @@ -1004,6 +1042,7 @@ static void xe_vma_destroy_late(struct xe_vma *vma)
>>   			unpin_user_pages_dirty_lock(vma->userptr.pinned_pages,
>>   						    vma->userptr.num_pinned,
>>   						    !read_only);
>> +			xe_vma_mlock_free(vma, xe_vma_size(vma) >> PAGE_SHIFT);
>>   			kvfree(vma->userptr.pinned_pages);
>>   		}
>>   
>> -- 
>> 2.41.0
>>