linux-kernel - Re: [PATCH v4 05/36] mm: Add default definition of set

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Message-ID: <ZG7evKeOquNaxESl@casper.infradead.org>
Date:   Thu, 25 May 2023 05:06:20 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...nel.org>
Subject: Re: [PATCH v4 05/36] mm: Add default definition of set_ptes()

On Thu, May 25, 2023 at 08:31:14AM +0530, Anshuman Khandual wrote:
> > +#ifndef set_ptes
> > +#ifdef PFN_PTE_SHIFT
> > +/**
> > + * set_ptes - Map consecutive pages to a contiguous range of addresses.
> > + * @mm: Address space to map the pages into.
> > + * @addr: Address to map the first page at.
> > + * @ptep: Page table pointer for the first entry.
> > + * @pte: Page table entry for the first page.
> > + * @nr: Number of pages to map.
> > + *
> > + * May be overridden by the architecture, or the architecture can define
> > + * set_pte() and PFN_PTE_SHIFT.
> > + *
> > + * Context: The caller holds the page table lock.  The pages all belong
> > + * to the same folio.  The PTEs are all in the same PMD.
> > + */
> > +static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
> > +		pte_t *ptep, pte_t pte, unsigned int nr)
> > +{
> > +	page_table_check_ptes_set(mm, addr, ptep, pte, nr);
> > +
> > +	for (;;) {
> > +		set_pte(ptep, pte);
> > +		if (--nr == 0)
> > +			break;
> > +		ptep++;
> > +		pte = __pte(pte_val(pte) + (1UL << PFN_PTE_SHIFT));
> > +	}
> > +}
> > +#ifndef set_pte_at
> > +#define set_pte_at(mm, addr, ptep, pte) set_ptes(mm, addr, ptep, pte, 1)
> > +#endif
> 
> Should not there be a build phase call out when both set_ptes() and PFN_PTE_SHIFT
> are not defined on a given platform ?

How does that help?  Either way you get a clear build error.