The patch titled
Subject: powerpc/e500: don't pre-check write access on data TLB error
has been added to the -mm mm-unstable branch. Its filename is
powerpc-e500-dont-pre-check-write-access-on-data-tlb-error.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/powerpc-e500-dont-pre-check-write-access-on-data-tlb-error.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Subject: powerpc/e500: don't pre-check write access on data TLB error
Date: Tue, 2 Jul 2024 15:51:30 +0200
Don't pre-check write access on read-only pages on data TLB error.
Load the TLB anyway and take a DSI exception when it happens. This avoids
reading SPRN_ESR at every data TLB error exception.
Link: https://lkml.kernel.org/r/8525518e1657d6032b7e980c1888102828d66950.1719928057.git.christophe.leroy@xxxxxxxxxx
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/head_85xx.S | 15 ---------------
1 file changed, 15 deletions(-)
--- a/arch/powerpc/kernel/head_85xx.S~powerpc-e500-dont-pre-check-write-access-on-data-tlb-error
+++ a/arch/powerpc/kernel/head_85xx.S
@@ -472,27 +472,12 @@ END_BTB_FLUSH_SECTION
#endif
4:
- /* Mask of required permission bits. Note that while we
- * do copy ESR:ST to _PAGE_WRITE position as trying to write
- * to an RO page is pretty common, we don't do it with
- * _PAGE_DIRTY. We could do it, but it's a fairly rare
- * event so I'd rather take the overhead when it happens
- * rather than adding an instruction here. We should measure
- * whether the whole thing is worth it in the first place
- * as we could avoid loading SPRN_ESR completely in the first
- * place...
- *
- * TODO: Is it worth doing that mfspr & rlwimi in the first
- * place or can we save a couple of instructions here ?
- */
- mfspr r12,SPRN_ESR
#ifdef CONFIG_PTE_64BIT
li r13,_PAGE_PRESENT|_PAGE_BAP_SR
oris r13,r13,_PAGE_ACCESSED@h
#else
li r13,_PAGE_PRESENT|_PAGE_READ|_PAGE_ACCESSED
#endif
- rlwimi r13,r12,11,29,29
FIND_PTE
andc. r13,r13,r11 /* Check permission */
_
Patches currently in -mm which might be from christophe.leroy@xxxxxxxxxx are
mm-define-__pte_leaf_size-to-also-take-a-pmd-entry.patch
mm-provide-mm_struct-and-address-to-huge_ptep_get.patch
powerpc-mm-remove-_page_psize.patch
powerpc-mm-fix-__find_linux_pte-on-32-bits-with-pmd-leaf-entries.patch
powerpc-mm-allow-hugepages-without-hugepd.patch
powerpc-8xx-fix-size-given-to-set_huge_pte_at.patch
powerpc-8xx-rework-support-for-8m-pages-using-contiguous-pte-entries.patch
powerpc-8xx-simplify-struct-mmu_psize_def.patch
powerpc-e500-remove-enc-and-ind-fields-from-struct-mmu_psize_def.patch
powerpc-e500-switch-to-64-bits-pgd-on-85xx-32-bits.patch
powerpc-e500-encode-hugepage-size-in-pte-bits.patch
powerpc-e500-dont-pre-check-write-access-on-data-tlb-error.patch
powerpc-e500-free-r10-for-find_pte.patch
powerpc-e500-use-contiguous-pmd-instead-of-hugepd.patch
powerpc-64s-use-contiguous-pmd-pud-instead-of-hugepd.patch
powerpc-mm-remove-hugepd-leftovers.patch
mm-remove-config_arch_has_hugepd.patch
