Hi,

On Fri, May 22, 2020 at 10:23:09PM -0700, Mike Rapoport wrote:

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.

Fixes: 7235db268a2777bc38 ("sparc32: use pgtable-nopud instead of 4level-fixup") Reported-by: kbuild test robot lkp@intel.com Signed-off-by: Mike Rapoport rppt@linux.ibm.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Cc: David S. Miller davem@davemloft.net Cc: Anatoly Pugachev matorola@gmail.com Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20200520132005.GM1059226@linux.ibm.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org

---

arch/sparc/mm/srmmu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c index b7c94de70cca..e9f7af32da07 100644 --- a/arch/sparc/mm/srmmu.c +++ b/arch/sparc/mm/srmmu.c @@ -333,7 +333,7 @@ static void __init srmmu_nocache_init(void) 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);
  

• pmd = pmd_offset(__nocache_fix(pud), vaddr);
  

  pte = pte_offset_kernel(__nocache_fix(pmd), vaddr);

pteval = ((paddr >> 4) | SRMMU_ET_PTE | SRMMU_PRIV); -- 2.17.1

This quite innocent looking patch crashes all my sparc32 boot tests. Crash log and bisect results below. Reverting it fixes the problem.

Guenter

--- # bad: [423b8baf18a8c03f2d6fa99aa447ed0da189bb95] Merge branch 'akpm' (patches from Andrew) # good: [051143e1602d90ea71887d92363edd539d411de5] Merge tag 'apparmor-pr-2020-05-21' of git://git.kernel.org/pub/scm/linux/kernel/git/jj/linux-apparmor git bisect start 'HEAD' '051143e1602d' # good: [e644645abf4788e919beeb97925fb6bf43e890a2] Merge tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi git bisect good e644645abf4788e919beeb97925fb6bf43e890a2 # good: [8f261041b18ee80ad8afdd1621c909c4df9f6cc3] Merge tag 'staging-5.7-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging git bisect good 8f261041b18ee80ad8afdd1621c909c4df9f6cc3 # good: [23f0dac848412dafd197566b62d831d5a68b5b6b] Merge tag 'driver-core-5.7-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core git bisect good 23f0dac848412dafd197566b62d831d5a68b5b6b # good: [33cd65e73abd693c00c4156cf23677c453b41b3b] kasan: disable branch tracing for core runtime git bisect good 33cd65e73abd693c00c4156cf23677c453b41b3b # bad: [c2bc26f7ca1ff1165bb6669a7a4cccc20ffd2ced] sparc32: use PUD rather than PGD to get PMD in srmmu_nocache_init() git bisect bad c2bc26f7ca1ff1165bb6669a7a4cccc20ffd2ced # good: [f7fa1876af81512444631d324adb77383f56c37a] MAINTAINERS: update email address for Naoya Horiguchi git bisect good f7fa1876af81512444631d324adb77383f56c37a # first bad commit: [c2bc26f7ca1ff1165bb6669a7a4cccc20ffd2ced] sparc32: use PUD rather than PGD to get PMD in srmmu_nocache_init()

--- Configuration device id QEMU version 1 machine id 36 Probing SBus slot 0 offset 0 Probing SBus slot 1 offset 0 Probing SBus slot 2 offset 0 Probing SBus slot 3 offset 0 Probing SBus slot 4 offset 0 Probing SBus slot 5 offset 0 Invalid FCode start byte CPUs: 1 x FMI,MB86904 UUID: 00000000-0000-0000-0000-000000000000 Welcome to OpenBIOS v1.1 built on Oct 28 2019 17:08 Type 'help' for detailed information [sparc] Kernel already loaded switching to new context: PROMLIB: obio_ranges 1 PROMLIB: Sun Boot Prom Version 3 Revision 2 Linux version 5.7.0-rc6-00161-g423b8baf18a8 (groeck@server.roeck-us.net) (gcc version 6.5.0 (Buildroot 2018.11-rc2-00071-g4310260), GNU ld (GNU Binutils) 2.31.1) #1 Sat May 23 11:57:22 PDT 2020 printk: bootconsole [earlyprom0] enabled ARCH: SUN4M TYPE: SPARCstation Classic Ethernet address: 52:54:00:12:34:56 Unable to handle kernel paging request at virtual address d9440000 tsk->{mm,active_mm}->context = ffffffff tsk->{mm,active_mm}->pgd = fc000000 |/ ____ |/ "@'/ ,. `@" /_| __/ |_\ __U_/ swapper(0): Oops [#1] CPU: 0 PID: 0 Comm: swapper Not tainted 5.7.0-rc6-00161-g423b8baf18a8 #1 PSR: 04901fc3 PC: f06592a0 NPC: f06592a4 Y: 00000000 Not tainted PC: <srmmu_paging_init+0x450/0xba0> %G: 00000008 f06c0000 00000000 cd4403f0 fc000000 006c0000 f0622000 ec000000 %O: 0006c200 000003f0 0c000000 f06c0000 00000000 00001000 f0623d48 0c000000 RPC: <0xc000000> %L: f067f000 f067f1d4 f067f000 f067f344 0fffffff 0000000f 14000000 fc0003f0 %I: f0000000 f0636698 04000000 f067f000 f067f000 f067f000 f0623e68 f06585dc Disabling lock debugging due to kernel taint Caller[f06585dc]: paging_init+0x4/0x24 Caller[f06565b8]: setup_arch+0x430/0x468 Caller[f0652b98]: start_kernel+0x48/0x520 Caller[f065243c]: continue_boot+0x324/0x334 Caller[00000000]: 0x0 Instruction DUMP: 8600c001 8600c001 8600c001 <c600c00a> 8088c018 12800007 9a103fff 8728e004 9a21c002 Kernel panic - not syncing: Attempted to kill the idle task! Press Stop-A (L1-A) from sun keyboard or send break twice on console to return to the boot prom ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---