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SubjectRe: [PATCH v2 2/4] ioremap: Implement TLB_INV before huge mapping
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On 3/15/2018 7:01 PM, Mark Rutland wrote:
> On Thu, Mar 15, 2018 at 06:15:04PM +0530, Chintan Pandya wrote:
>> @@ -91,10 +93,15 @@ static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
>>
>> if (ioremap_pmd_enabled() &&
>> ((next - addr) == PMD_SIZE) &&
>> - IS_ALIGNED(phys_addr + addr, PMD_SIZE) &&
>> - pmd_free_pte_page(pmd)) {
>> - if (pmd_set_huge(pmd, phys_addr + addr, prot))
>> + IS_ALIGNED(phys_addr + addr, PMD_SIZE)) {
>> + old_pmd = *pmd;
>> + pmd_clear(pmd);
>> + flush_tlb_pgtable(&init_mm, addr);
>> + if (pmd_set_huge(pmd, phys_addr + addr, prot)) {
>> + pmd_free_pte_page(&old_pmd);
>> continue;
>> + } else
>> + set_pmd(pmd, old_pmd);
>> }
>>
>
> Can we have something like a pmd_can_set_huge() helper? Then we could
> avoid pointless modification and TLB invalidation work when
> pmd_set_huge() will fail.

Actually, pmd_set_huge() will never fail because, if
CONFIG_HAVE_ARCH_HUGE_VMAP is disabled, ioremap_pmd_enabled()
will fail and if enabled (i.e. ARM64 & x86), they don't fail
in their implementation. So, rather we can do the following.

- if (pmd_set_huge(pmd, phys_addr + addr, prot)) {
- pmd_free_pte_page(&old_pmd);
- continue;
- } else
- set_pmd(pmd, old_pmd);
+ pmd_set_huge(pmd, phys_addr + addr, prot)
+ pmd_free_pte_page(&old_pmd);
+ continue;

>
> if (ioremap_pmd_enabled() &&
> ((next - addr) == PMD_SIZE) &&
> IS_ALIGNED(phys_addr + addr, PMD_SIZE) &&
> pmd_can_set_huge(pmd, phys_addr + addr, prot)) {
> // clear entries, invalidate TLBs, and free tables
> ...
> continue;
>
> }
>
> Thanks,
> MArk.
>
> _______________________________________________
> 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

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