Messages in this thread | | | Date | Wed, 28 Jan 2015 12:10:17 +0000 | From | Catalin Marinas <> | Subject | Re: [PATCHv2] arm64:mm: free the useless initial page table |
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On Fri, Jan 23, 2015 at 05:40:40PM +0000, Ard Biesheuvel wrote: > On 23 January 2015 at 16:21, Catalin Marinas <catalin.marinas@arm.com> wrote: > > On Tue, Dec 09, 2014 at 07:26:47AM +0000, zhichang.yuan@linaro.org wrote: > >> From: "zhichang.yuan" <zhichang.yuan@linaro.org> > >> > >> For 64K page system, after mapping a PMD section, the corresponding initial > >> page table is not needed any more. That page can be freed. > >> > >> Changes since v1: > >> > >> * make consistent code between alloc_init_pmd and alloc_init_pud; > >> * flush the TLB before the unused page table is freed; > >> > >> Signed-off-by: Zhichang Yuan <zhichang.yuan@linaro.org> > > > > I thought about queuing this patch but I realised that > > alloc_init_pmd/pud may be called in a late context where memblock_free() > > would no longer make sense. Cc'ing Laura and Ard for any ideas here but > > I think we may just end up with a few old page table pages sitting > > around (not many though). In general we don't go from smaller to larger > > mappings (that's what this patch targets) but given the API, I'm not > > sure we have any guarantee. > > > > One solution would be to check for alloc == early_alloc or something > > similar. Cc'ing Laura and Ard as they added the create_mapping_late() > > code. > > > > The UEFI page tables are only built up once, based on a series of > disjoint memory regions, so that will never hit either of the > memblock_free() branches. > And AFAICT, the DEBUG_RODATA code does the splitting early, which > causes the create_mapping_late() code to only change permissions, not > change the granularity of any regions. > > Perhaps it's sufficient to add a comment and a BUG_ON(alloc != > early_alloc) to the memblock_free() branches?
Thanks for confirming, I merged this patch together with BUG_ON(), just in case.
-- Catalin
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