On 3/31/22 12:26, Muchun Song wrote:
> --- a/arch/arm64/mm/flush.c
> +++ b/arch/arm64/mm/flush.c
> @@ -68,6 +68,19 @@ EXPORT_SYMBOL_GPL(__sync_icache_dcache);
> */
> void flush_dcache_page(struct page *page)
> {
> + /*
> + * Only the head page's flags of HugeTLB can be cleared since the tail
> + * vmemmap pages associated with each HugeTLB page are mapped with
> + * read-only when CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is enabled (more
> + * details can refer to vmemmap_remap_pte()). Although
Did you see real permission fault when flush_dcache_page() accessed remapped
tail pages, with readonly vmemmap ? OR this change is from code inspection ?
> + * __sync_icache_dcache() only set PG_dcache_clean flag on the head
> + * page struct, some tail page structs still can be seen the flag is
Sentence here needs restructuring .... ^^^^^^^^^^^^^^^^^^
> + * set since the head vmemmap page frame is reused (more details can
> + * refer to the comments above page_fixed_fake_head()).
> + */
> + if (hugetlb_free_vmemmap_enabled() && PageHuge(page))
> + page = compound_head(page);
This should also be applicable to any other platform with both configs enabled
i.e ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE and ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP ?
If yes, then how to ensure that the platforms change flush_dcache_page() before
subscribing into ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP ?
> +
> if (test_bit(PG_dcache_clean, &page->flags))
> clear_bit(PG_dcache_clean, &page->flags);
> }
