Re: [PATCH v2 2/4] drm/gem-shmem: Map pages in mmap fault handler

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi,

I came across commit 8b93d1d7dbd5 ("drm/shmem-helper: Switch to 
vmf_insert_pfn") from 2021, which makes it very clear the PFNMAP is 
strongly preferred over pages. I totally forgot about that change. The 
next iteration of this series will therefore not contain this patch.

Best regards
Thomas

Am 04.02.26 um 17:03 schrieb Matthew Wilcox:
> On Wed, Feb 04, 2026 at 12:39:30PM +0100, Thomas Zimmermann wrote:
>> +	ret = drm_gem_shmem_try_map_pmd(vmf, vmf->address, page);
>> +	if (ret != VM_FAULT_NOPAGE) {
>> +		struct folio *folio = page_folio(page);
>> +
>> +		get_page(page);
> folio_get(folio);
>
>> -	pfn = page_to_pfn(pages[page_offset]);
>> -	ret = vmf_insert_pfn(vma, vmf->address, pfn);
>> +		folio_lock(folio);
>> +
>> +		vmf->page = page;
>> +		ret = VM_FAULT_LOCKED;
>> +	}
>>   
>> - out:
>> +out:
>>   	dma_resv_unlock(shmem->base.resv);
>>   
>>   	return ret;
>> @@ -689,7 +698,7 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
>>   	if (ret)
>>   		return ret;
>>   
>> -	vm_flags_set(vma, VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
>> +	vm_flags_mod(vma, VM_DONTEXPAND | VM_DONTDUMP, VM_PFNMAP);
> Do you need to explicitly clear VM_PFNMAP here?  I'm not familiar with
> the DRM stack; maybe that's set for you higher in the stack.
>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)