On Fri, May 22, 2020 at 10:23:09PM -0700, Andrew Morton wrote: > From: Mike Rapoport <rppt@xxxxxxxxxxxxx> > Subject: sparc32: use PUD rather than PGD to get PMD in srmmu_nocache_init() > > The kbuild test robot reported the following warning: > > arch/sparc/mm/srmmu.c: In function 'srmmu_nocache_init': > >> arch/sparc/mm/srmmu.c:300:9: error: variable 'pud' set but not used > >> [-Werror=unused-but-set-variable] > 300 | pud_t *pud; > > This warning is caused by misprint in the page table traversal in > srmmu_nocache_init() function which accessed a PMD entry using PGD rather > than PUD. > > Since sparc32 has only 3 page table levels, the PGD and PUD are > essentially the same and usage of __nocache_fix() removed the type > checking. > > Use PUD for the consistency and to silence the compiler warning. Unfortunately, this fixes a compile warning but breaks the boot :( Since pgd, p4d and pud are eesentially the same thing and pgd_offset() and p4d_offset() are no-ops, the __nocache_fix() should be done only at pud level. The correcteted patch is below, boot tested with qemu-systems-sparc. > Link: http://lkml.kernel.org/r/20200520132005.GM1059226@xxxxxxxxxxxxx > Fixes: 7235db268a2777bc38 ("sparc32: use pgtable-nopud instead of 4level-fixup") > Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> > Reported-by: kbuild test robot <lkp@xxxxxxxxx> > Cc: David S. Miller <davem@xxxxxxxxxxxxx> > Cc: Anatoly Pugachev <matorola@xxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- >From 9b8b3214f7f079864dca0c6a7b684ab442eeb437 Mon Sep 17 00:00:00 2001 From: Mike Rapoport <rppt@xxxxxxxxxxxxx> Date: Wed, 20 May 2020 15:39:22 +0300 Subject: [PATCH] sparc32: use PUD rather than PGD to get PMD in srmmu_nocache_init() The kbuild test robot reported the following warning: arch/sparc/mm/srmmu.c: In function 'srmmu_nocache_init': >> arch/sparc/mm/srmmu.c:300:9: error: variable 'pud' set but not used >> [-Werror=unused-but-set-variable] 300 | pud_t *pud; This warning is caused by misprint in the page table traversal in srmmu_nocache_init() function which accessed a PMD entry using PGD rather than PUD. Since pgd, p4d and pud are eesentially the same thing and pgd_offset() and p4d_offset() are no-ops, the __nocache_fix() should be done only at pud level. Remove __nocache_fix() for p4d_offset() and pud_offset() and use it only for PUD and lower levels. Link: http://lkml.kernel.org/r/20200520132005.GM1059226@xxxxxxxxxxxxx Fixes: 7235db268a2777bc38 ("sparc32: use pgtable-nopud instead of 4level-fixup") Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> Reported-by: kbuild test robot <lkp@xxxxxxxxx> Cc: David S. Miller <davem@xxxxxxxxxxxxx> Cc: Anatoly Pugachev <matorola@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> --- arch/sparc/mm/srmmu.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c index 6cb1ea2d2b5c..3d9690d940a3 100644 --- a/arch/sparc/mm/srmmu.c +++ b/arch/sparc/mm/srmmu.c @@ -302,9 +302,9 @@ static void __init srmmu_nocache_init(void) while (vaddr < srmmu_nocache_end) { pgd = pgd_offset_k(vaddr); - p4d = p4d_offset(__nocache_fix(pgd), vaddr); - pud = pud_offset(__nocache_fix(p4d), vaddr); - pmd = pmd_offset(__nocache_fix(pgd), vaddr); + p4d = p4d_offset(pgd, vaddr); + pud = pud_offset(p4d, vaddr); + pmd = pmd_offset(__nocache_fix(pud), vaddr); pte = pte_offset_kernel(__nocache_fix(pmd), vaddr); pteval = ((paddr >> 4) | SRMMU_ET_PTE | SRMMU_PRIV); -- 2.26.2
