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Date: Thu, 26 Nov 2020 11:46:51 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Christophe Leroy <christophe.leroy@...roup.eu> Cc: kan.liang@...ux.intel.com, mingo@...nel.org, acme@...nel.org, mark.rutland@....com, alexander.shishkin@...ux.intel.com, jolsa@...hat.com, eranian@...gle.com, npiggin@...il.com, linuxppc-dev@...ts.ozlabs.org, mpe@...erman.id.au, will@...nel.org, willy@...radead.org, aneesh.kumar@...ux.ibm.com, sparclinux@...r.kernel.org, davem@...emloft.net, catalin.marinas@....com, linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org, ak@...ux.intel.com, dave.hansen@...el.com, kirill.shutemov@...ux.intel.com Subject: Re: [PATCH 0/5] perf/mm: Fix PERF_SAMPLE_*_PAGE_SIZE On Fri, Nov 20, 2020 at 01:20:04PM +0100, Peter Zijlstra wrote: > > > I can help with powerpc 8xx. It is a 32 bits powerpc. The PGD has 1024 > > > entries, that means each entry maps 4M. > > > > > > Page sizes are 4k, 16k, 512k and 8M. > > > > > > For the 8M pages we use hugepd with a single entry. The two related PGD > > > entries point to the same hugepd. > > > > > > For the other sizes, they are in standard page tables. 16k pages appear > > > 4 times in the page table. 512k entries appear 128 times in the page > > > table. > > > > > > When the PGD entry has _PMD_PAGE_8M bits, the PMD entry points to a > > > hugepd with holds the single 8M entry. > > > > > > In the PTE, we have two bits: _PAGE_SPS and _PAGE_HUGE > > > > > > _PAGE_HUGE means it is a 512k page > > > _PAGE_SPS means it is not a 4k page > > > > > > The kernel can by build either with 4k pages as standard page size, or > > > 16k pages. It doesn't change the page table layout though. > > > > > > Hope this is clear. Now I don't really know to wire that up to your series. Does the below accurately reflect things? Let me go find a suitable cross-compiler .. diff --git a/arch/powerpc/include/asm/nohash/32/pte-8xx.h b/arch/powerpc/include/asm/nohash/32/pte-8xx.h index 1581204467e1..fcc48d590d88 100644 --- a/arch/powerpc/include/asm/nohash/32/pte-8xx.h +++ b/arch/powerpc/include/asm/nohash/32/pte-8xx.h @@ -135,6 +135,29 @@ static inline pte_t pte_mkhuge(pte_t pte) } #define pte_mkhuge pte_mkhuge + +static inline unsigned long pgd_leaf_size(pgd_t pgd) +{ + if (pgd_val(pgd) & _PMD_PAGE_8M) + return SZ_8M; + return SZ_4M; +} + +#define pgd_leaf_size pgd_leaf_size + +static inline unsigned long pte_leaf_size(pte_t pte) +{ + pte_basic_t val = pte_val(pte); + + if (val & _PAGE_HUGE) + return SZ_512K; + if (val & _PAGE_SPS) + return SZ_16K; + return SZ_4K; +} + +#define pte_leaf_size pte_leaf_size + #endif #endif /* __KERNEL__ */
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