linux-kernel - Re: [PATCH v3 07/13] mm: introduce io_remap_pfn_range

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Message-ID: <07448a14-68f9-4577-9c00-36f63c1f2e90@lucifer.local>
Date: Tue, 16 Sep 2025 18:34:20 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>, Matthew Wilcox <willy@...radead.org>,
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Subject: Re: [PATCH v3 07/13] mm: introduce io_remap_pfn_range_[prepare,
 complete]()

On Tue, Sep 16, 2025 at 02:19:30PM -0300, Jason Gunthorpe wrote:
> On Tue, Sep 16, 2025 at 03:11:53PM +0100, Lorenzo Stoakes wrote:
> >
> > -int io_remap_pfn_range(struct vm_area_struct *vma, unsigned long vaddr,
> > -		unsigned long pfn, unsigned long size, pgprot_t prot)
> > +static unsigned long calc_pfn(unsigned long pfn, unsigned long size)
> >  {
> >  	phys_addr_t phys_addr = fixup_bigphys_addr(pfn << PAGE_SHIFT, size);
> >
> > -	return remap_pfn_range(vma, vaddr, phys_addr >> PAGE_SHIFT, size, prot);
> > +	return phys_addr >> PAGE_SHIFT;
> > +}
>
> Given you changed all of these to add a calc_pfn why not make that
> the arch abstraction?

OK that's reasonable, will do.

>
> static unsigned long arch_io_remap_remap_pfn(unsigned long pfn, unsigned long size)
> {
> ..
> }
> #define arch_io_remap_remap_pfn arch_io_remap_remap_pfn
>
> [..]
>
> #ifndef arch_io_remap_remap_pfn
> static inline unsigned long arch_io_remap_remap_pfn(unsigned long pfn, unsigned long size)
> {
> 	return pfn;
> }
> #endif
>
> static inline void io_remap_pfn_range_prepare(struct vm_area_desc *desc, unsigned long pfn,
> 	unsigned long size)
> {
> 	return remap_pfn_range_prepare(desc, arch_io_remap_remap_pfn(pfn));
> }
>
> etc
>
> Removes alot of the maze here.

Actually nice to restrict what arches can do here also... :)

>
> Jason