On Fri, May 22, 2020 at 10:23:09PM -0700, Andrew Morton wrote:
From: Mike Rapoport rppt@linux.ibm.com 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@linux.ibm.com Fixes: 7235db268a2777bc38 ("sparc32: use pgtable-nopud instead of 4level-fixup") Signed-off-by: Mike Rapoport rppt@linux.ibm.com Reported-by: kbuild test robot lkp@intel.com Cc: David S. Miller davem@davemloft.net Cc: Anatoly Pugachev matorola@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org
From 9b8b3214f7f079864dca0c6a7b684ab442eeb437 Mon Sep 17 00:00:00 2001
From: Mike Rapoport rppt@linux.ibm.com 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@linux.ibm.com Fixes: 7235db268a2777bc38 ("sparc32: use pgtable-nopud instead of 4level-fixup") Signed-off-by: Mike Rapoport rppt@linux.ibm.com Reported-by: kbuild test robot lkp@intel.com Cc: David S. Miller davem@davemloft.net Cc: Anatoly Pugachev matorola@gmail.com Cc: stable@vger.kernel.org --- 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);