Re: [PATCH RFT 0/3] mm, drm: ensure .fault() does not have to be followed by .pfn_mkwrite() for write faults

[David Hildenbrand (Arm)]

On 7/31/26 18:43, Paolo Bonzini wrote:
> Warning - DRM parts (i.e. most of the patches) untested; I have Cc'd
> the reporter to help with testing these patches.
> 
> Right now, users of .pfn_mkwrite() have no way to create a PTE
> that has gone through maybe_mkwrite().  Because vma_set_page_prot()
> will have cleared the writable PTE bit, users of fixup_user_fault()
> will see a read-only PTE and have no clue that the page needs
> a *second* fault to reach its final status.
> 
> Handling this in fixup_user_fault() is problematic: the information
> about the presence of *_mkwrite is only recorded in vma->vm_page_prot,
> which is an opaque pgprot_t, therefore only follow_pfnmap_start()
> knows how to retrieve it.

How is mprotect() supposed to work in that case?

-- 
Cheers,

David