Messages in this thread | | | Date | Thu, 13 Sep 2018 18:50:21 +0800 | From | Jun Yao <> | Subject | Re: [RESEND PATCH v4 5/6] arm64/mm: Populate the swapper_pg_dir by fixmap. |
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Hi James,
On Fri, Sep 07, 2018 at 10:58:22AM +0100, James Morse wrote: > On 22/08/18 10:54, Jun Yao wrote: > > WRITE_ONCE(*pmdp, pmd); > > dsb(ishst); > > } > > @@ -480,6 +511,19 @@ static inline phys_addr_t pmd_page_paddr(pmd_t pmd) > > > > static inline void set_pud(pud_t *pudp, pud_t pud) > > { > > +#ifdef __PAGETABLE_PUD_FOLDED > > + if (in_swapper_pgdir(pudp)) { > > + pud_t *fixmap_pudp; > > + > > + spin_lock(&swapper_pgdir_lock); > > + fixmap_pudp = (pud_t *)pgd_set_fixmap(__pa(pudp)); > > I see this called 68 times during boot on a 64K/42bit-VA, 65 of which appear to > be during paging_init(). What do you think to keeping paging_init()s use of the > pgd fixmap for swapper_pg_dir, deliberately to skip the in_swapper_pgdir() test > during paging_init()?
I find that the __create_pgd_mapping() is used to set up the page table during paging_init(). And there are six functions calling it with different pgdps:
update_mapping_prot() init_mm.pgd(swapper_pg_dir) create_mapping_noalloc() init_mm.pgd(swapper_pg_dir) __map_memblock() pgdp(swapper_pg_dir) map_kernel_segment() pgdp(swapper_pg_dir) create_pgd_mapping() !(init_mm.pgd) map_entry_trampoline() tramp_pg_dir
In order to skip the in_swapper_pgdir() test during paging_init(), We need a way to determine if we are currently in paging_init(). The way I can think of is to create a function similar to __create_pgd_mapping(). And it is used to create the page table during paging_init(). It differs from the __create_pgd_mapping() only in that it calls p?d_populate_without_test(). However, in this way, I'm worried that I am reinventing the wheel.
Thanks,
Jun
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