linux-kernel - Re: [PATCH v5 05/17] arm64: pgtable: use mmu gather to free p4d level page table

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Message-ID: <20250117132527.GA17058@willie-the-truck>
Date: Fri, 17 Jan 2025 13:25:28 +0000
From: Will Deacon <will@...nel.org>
To: Qi Zheng <zhengqi.arch@...edance.com>
Cc: peterz@...radead.org, agordeev@...ux.ibm.com, kevin.brodsky@....com,
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Subject: Re: [PATCH v5 05/17] arm64: pgtable: use mmu gather to free p4d
 level page table

On Tue, Jan 14, 2025 at 10:26:54AM +0800, Qi Zheng wrote:
> Hi Will,
> 
> On 2025/1/14 00:26, Will Deacon wrote:
> > On Wed, Jan 08, 2025 at 02:57:21PM +0800, Qi Zheng wrote:
> > > Like other levels of page tables, also use mmu gather mechanism to free
> > > p4d level page table.
> > > 
> > > Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> > > Originally-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > > Reviewed-by: Kevin Brodsky <kevin.brodsky@....com>
> > > Cc: linux-arm-kernel@...ts.infradead.org
> > > ---
> > >   arch/arm64/include/asm/pgalloc.h |  1 -
> > >   arch/arm64/include/asm/tlb.h     | 14 ++++++++++++++
> > >   2 files changed, 14 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h
> > > index 2965f5a7e39e3..1b4509d3382c6 100644
> > > --- a/arch/arm64/include/asm/pgalloc.h
> > > +++ b/arch/arm64/include/asm/pgalloc.h
> > > @@ -85,7 +85,6 @@ static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgdp, p4d_t *p4dp)
> > >   	__pgd_populate(pgdp, __pa(p4dp), pgdval);
> > >   }
> > > -#define __p4d_free_tlb(tlb, p4d, addr)  p4d_free((tlb)->mm, p4d)
> > >   #else
> > >   static inline void __pgd_populate(pgd_t *pgdp, phys_addr_t p4dp, pgdval_t prot)
> > >   {
> > > diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
> > > index a947c6e784ed2..445282cde9afb 100644
> > > --- a/arch/arm64/include/asm/tlb.h
> > > +++ b/arch/arm64/include/asm/tlb.h
> > > @@ -111,4 +111,18 @@ static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pudp,
> > >   }
> > >   #endif
> > > +#if CONFIG_PGTABLE_LEVELS > 4
> > > +static inline void __p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4dp,
> > > +				  unsigned long addr)
> > > +{
> > > +	struct ptdesc *ptdesc = virt_to_ptdesc(p4dp);
> > > +
> > > +	if (!pgtable_l5_enabled())
> > > +		return;
> > > +
> > > +	pagetable_p4d_dtor(ptdesc);
> > > +	tlb_remove_ptdesc(tlb, ptdesc);
> > > +}
> > 
> > Should we update p4d_free() to call the destructor, too? It looks like
> > it just does free_page() atm.
> 
> The patch #3 introduces the generic p4d_free() and lets arm64 to use it.
> The patch #4 adds the destructor to generic p4d_free(). So IIUC, there
> is no problem here.

Sorry, I missed that. In which case:

Acked-by: Will Deacon <will@...nel.org>

Will