Re: [PATCH -fixes 2/2] riscv: Fix set_huge_pte_at() for NAPOT mappings when a swap entry is set

[Alexandre Ghiti]

Hi Conor,

On 30/09/2023 11:14, Conor Dooley wrote:
> On Thu, Sep 28, 2023 at 05:18:46PM +0200, Alexandre Ghiti wrote:
> > We used to determine the number of page table entries to set for a NAPOT
> > hugepage by using the pte value which actually fails when the pte to set is
> > a swap entry.
> >
> > So take advantage of a recent fix for arm64 reported in [1] which
> > introduces the size of the mapping as an argument of set_huge_pte_at(): we
> > can then use this size to compute the number of page table entries to set
> > for a NAPOT region.
> >
> > Fixes: 82a1a1f3bfb6 ("riscv: mm: support Svnapot in hugetlb page")
> > Reported-by: Ryan Roberts <ryan.roberts@xxxxxxx>
> > Closes: https://lore.kernel.org/linux-arm-kernel/20230922115804.2043771-1-ryan.roberts@xxxxxxx/ [1]
> > Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
> Breaks the build. Your $subject marks this for -fixes, but this will not
> build there, as it relies on content that's not yet in that branch.
> AFAICT, you're going to have to resend this with akpm on CC, as the
> dependency is in his tree...


I see, but I still don't understand why -fixes does not point to the 
latest rcX instead of staying on rc1? The patch which this series 
depends on just made it to rc4.

Thanks,

Alex


> Thanks,
> Conor.
>
> > ---
> >   arch/riscv/mm/hugetlbpage.c | 19 +++++++++++++------
> >   1 file changed, 13 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/riscv/mm/hugetlbpage.c b/arch/riscv/mm/hugetlbpage.c
> > index e4a2ace92dbe..b52f0210481f 100644
> > --- a/arch/riscv/mm/hugetlbpage.c
> > +++ b/arch/riscv/mm/hugetlbpage.c
> > @@ -183,15 +183,22 @@ void set_huge_pte_at(struct mm_struct *mm,
> >   		     pte_t pte,
> >   		     unsigned long sz)
> >   {
> > +	unsigned long hugepage_shift;
> >   	int i, pte_num;
> >   
> > -	if (!pte_napot(pte)) {
> > -		set_pte_at(mm, addr, ptep, pte);
> > -		return;
> > -	}
> > +	if (sz >= PGDIR_SIZE)
> > +		hugepage_shift = PGDIR_SHIFT;
> > +	else if (sz >= P4D_SIZE)
> > +		hugepage_shift = P4D_SHIFT;
> > +	else if (sz >= PUD_SIZE)
> > +		hugepage_shift = PUD_SHIFT;
> > +	else if (sz >= PMD_SIZE)
> > +		hugepage_shift = PMD_SHIFT;
> > +	else
> > +		hugepage_shift = PAGE_SHIFT;
> >   
> > -	pte_num = napot_pte_num(napot_cont_order(pte));
> > -	for (i = 0; i < pte_num; i++, ptep++, addr += PAGE_SIZE)
> > +	pte_num = sz >> hugepage_shift;
> > +	for (i = 0; i < pte_num; i++, ptep++, addr += (1 << hugepage_shift))
> >   		set_pte_at(mm, addr, ptep, pte);
> >   }
> >   
> > --
> > 2.39.2
> >
> >
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