linux-kernel - Re: [PATCH v2 3/4] arm64: Implement page table free interfaces

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Message-ID: <20180315131846.sfpxg3xlpjii3nju@lakrids.cambridge.arm.com>
Date:   Thu, 15 Mar 2018 13:18:46 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Chintan Pandya <cpandya@...eaurora.org>
Cc:     catalin.marinas@....com, will.deacon@....com, arnd@...db.de,
        ard.biesheuvel@...aro.org, marc.zyngier@....com,
        james.morse@....com, kristina.martsenko@....com,
        takahiro.akashi@...aro.org, gregkh@...uxfoundation.org,
        tglx@...utronix.de, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        akpm@...ux-foundation.org, toshi.kani@....com
Subject: Re: [PATCH v2 3/4] arm64: Implement page table free interfaces

On Thu, Mar 15, 2018 at 06:15:05PM +0530, Chintan Pandya wrote:
> Implement pud_free_pmd_page() and pmd_free_pte_page().
> 
> Make sure, that they are indeed a page table before
> taking them to free.

As mentioned on the prior patch, if the tables we're freeing contain
valid entries, then we need additional TLB maintenance to ensure that
all of these entries have been removed from TLBs.

Either, we always invalidate the entire range, or we walk the tables
and invalidate as we remove them.

Thanks,
Mark.

> 
> Signed-off-by: Chintan Pandya <cpandya@...eaurora.org>
> ---
>  arch/arm64/mm/mmu.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 2dbb2c9..6f21a65 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -32,6 +32,7 @@
>  #include <linux/io.h>
>  #include <linux/mm.h>
>  #include <linux/vmalloc.h>
> +#include <linux/hugetlb.h>
>  
>  #include <asm/barrier.h>
>  #include <asm/cputype.h>
> @@ -45,6 +46,7 @@
>  #include <asm/memblock.h>
>  #include <asm/mmu_context.h>
>  #include <asm/ptdump.h>
> +#include <asm/page.h>
>  
>  #define NO_BLOCK_MAPPINGS	BIT(0)
>  #define NO_CONT_MAPPINGS	BIT(1)
> @@ -975,10 +977,24 @@ int pmd_clear_huge(pmd_t *pmdp)
>  
>  int pud_free_pmd_page(pud_t *pud)
>  {
> -	return pud_none(*pud);
> +	pmd_t *pmd;
> +	int i;
> +
> +	pmd = __va(pud_val(*pud));
> +	if (pud_val(*pud) && !pud_huge(*pud)) {
> +		for (i = 0; i < PTRS_PER_PMD; i++)
> +			pmd_free_pte_page(&pmd[i]);
> +
> +		free_page((unsigned long)pmd);
> +	}
> +
> +	return 1;
>  }
>  
>  int pmd_free_pte_page(pmd_t *pmd)
>  {
> -	return pmd_none(*pmd);
> +	if (pmd_val(*pmd) && !pmd_huge(*pmd))
> +		free_page((unsigned long)__va(pmd_val(*pmd)));
> +
> +	return 1;
>  }
> -- 
> Qualcomm India Private Limited, on behalf of Qualcomm Innovation
> Center, Inc., is a member of Code Aurora Forum, a Linux Foundation
> Collaborative Project
>