lkml.org 
[lkml]   [2018]   [May]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v9 3/4] arm64: Implement page table free interfaces
From
Date


On 5/23/2018 7:31 PM, Will Deacon wrote:
> Hi Chintan,

Hi Will,

>
> [as a side note: I'm confused on the status of this patch series, as part
> of it was reposted separately by Toshi. Please can you work together?]

I will share all 4 patches once again as v10 and take latest version of
1/4 as updated by Toshi.

>
> On Mon, Apr 30, 2018 at 01:11:33PM +0530, Chintan Pandya wrote:
>> Implement pud_free_pmd_page() and pmd_free_pte_page().
>>
>> Implementation requires,
>> 1) Clearing off the current pud/pmd entry
>> 2) Invalidate TLB which could have previously
>> valid but not stale entry
>> 3) Freeing of the un-used next level page tables
>>
>> Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>
>> ---
>> arch/arm64/mm/mmu.c | 29 +++++++++++++++++++++++++----
>> 1 file changed, 25 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index da98828..0f651db 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -45,6 +45,7 @@
>> #include <asm/memblock.h>
>> #include <asm/mmu_context.h>
>> #include <asm/ptdump.h>
>> +#include <asm/tlbflush.h>
>>
>> #define NO_BLOCK_MAPPINGS BIT(0)
>> #define NO_CONT_MAPPINGS BIT(1)
>> @@ -973,12 +974,32 @@ int pmd_clear_huge(pmd_t *pmdp)
>> return 1;
>> }
>>
>> -int pud_free_pmd_page(pud_t *pud, unsigned long addr)
>> +int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
>> {
>> - return pud_none(*pud);
>> + pmd_t *table;
>> +
>> + if (pmd_present(READ_ONCE(*pmdp))) {
>
> Might also be worth checking pmd_table here, just in case. (same for pud)

I had that check in v2 as below.

if (pud_val(*pud) && !pud_huge(*pud))

But removed that in v3 as unmap should change this to NONE if it is
not table. I still don't see the need of it.

>
>> + table = __va(pmd_val(*pmdp));
>
> Can you avoid dereferencing *pmdp twice, and instead READ_ONCE into a local
> variable, please? (same for pud)

Okay.

>
>> + pmd_clear(pmdp);
>> + __flush_tlb_kernel_pgtable(addr);
>> + free_page((unsigned long) table);
>
> Shouldn't this be pte_free_kernel, to pair with pte_alloc_kernel which
> was used to allocate the page in the first place? (similarly for pud)

Okay.

>
>> + }
>> + return 1;
>> }
>>
>> -int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
>> +int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
>> {
>> - return pmd_none(*pmd);
>> + pmd_t *table;
>> + int i;
>> +
>> + if (pud_present(READ_ONCE(*pudp))) {
>> + table = __va(pud_val(*pudp));
>> + for (i = 0; i < PTRS_PER_PMD; i++)
>> + pmd_free_pte_page(&table[i], addr + (i * PMD_SIZE));
>
> I think it would be cleaner to write this as a do { ... } while, for
> consistency with the ioremap and vmalloc code.

Okay.

I'll raise v10 fixing above things. Thanks for the review.

>
> Will
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>

Chintan
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc. is a member of the Code Aurora Forum, a Linux Foundation
Collaborative Project

\
 
 \ /
  Last update: 2018-05-24 09:35    [W:0.074 / U:0.204 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site