# git rev-parse -q --verify 53f1d31708f6240e4615b0927df31f182e389e2f^{commit}
53f1d31708f6240e4615b0927df31f182e389e2f
already have revision, skipping fetch
# git checkout -q -f -B kisskb 53f1d31708f6240e4615b0927df31f182e389e2f
# git clean -qxdf
# < git log -1
# commit 53f1d31708f6240e4615b0927df31f182e389e2f
# Author: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
# Date:   Fri Mar 26 12:37:55 2021 +0530
# 
#     powerpc/mm/book3s64: Use the correct storage key value when calling H_PROTECT
#     
#     H_PROTECT expects the flag value to include flags:
#       AVPN, pp0, pp1, pp2, key0-key4, Noexec, CMO Option flags
#     
#     This patch updates hpte_updatepp() to fetch the storage key value from
#     the linux page table and use the same in H_PROTECT hcall.
#     
#     native_hpte_updatepp() is not updated because the kernel doesn't clear
#     the existing storage key value there. The kernel also doesn't use
#     hpte_updatepp() callback for updating storage keys.
#     
#     This fixes the below kernel crash observed with KUAP enabled.
#     
#       BUG: Unable to handle kernel data access on write at 0xc009fffffc440000
#       Faulting instruction address: 0xc0000000000b7030
#       Key fault AMR: 0xfcffffffffffffff IAMR: 0xc0000077bc498100
#       Found HPTE: v = 0x40070adbb6fffc05 r = 0x1ffffffffff1194
#       Oops: Kernel access of bad area, sig: 11 [#1]
#       LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
#       ...
#       CFAR: c000000000010100 DAR: c009fffffc440000 DSISR: 02200000 IRQMASK: 0
#       ...
#       NIP memset+0x68/0x104
#       LR  pcpu_alloc+0x54c/0xb50
#       Call Trace:
#         pcpu_alloc+0x55c/0xb50 (unreliable)
#         blk_stat_alloc_callback+0x94/0x150
#         blk_mq_init_allocated_queue+0x64/0x560
#         blk_mq_init_queue+0x54/0xb0
#         scsi_mq_alloc_queue+0x30/0xa0
#         scsi_alloc_sdev+0x1cc/0x300
#         scsi_probe_and_add_lun+0xb50/0x1020
#         __scsi_scan_target+0x17c/0x790
#         scsi_scan_channel+0x90/0xe0
#         scsi_scan_host_selected+0x148/0x1f0
#         do_scan_async+0x2c/0x2a0
#         async_run_entry_fn+0x78/0x220
#         process_one_work+0x264/0x540
#         worker_thread+0xa8/0x600
#         kthread+0x190/0x1a0
#         ret_from_kernel_thread+0x5c/0x6c
#     
#     With KUAP enabled the kernel uses storage key 3 for all its
#     translations. But as shown by the debug print, in this specific case we
#     have the hash page table entry created with key value 0.
#     
#       Found HPTE: v = 0x40070adbb6fffc05 r = 0x1ffffffffff1194
#     
#     and DSISR indicates a key fault.
#     
#     This can happen due to parallel fault on the same EA by different CPUs:
#     
#       CPU 0                                 CPU 1
#       fault on X
#     
#       H_PAGE_BUSY set
#                                             fault on X
#     
#       finish fault handling and
#       clear H_PAGE_BUSY
#                                             check for H_PAGE_BUSY
#                                             continue with fault handling.
#     
#     This implies CPU1 will end up calling hpte_updatepp for address X and
#     the kernel updated the hash pte entry with key 0
#     
#     Fixes: d94b827e89dc ("powerpc/book3s64/kuap: Use Key 3 for kernel mapping with hash translation")
#     Reported-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
#     Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
#     Debugged-by: Michael Ellerman <mpe@ellerman.id.au>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
#     Link: https://lore.kernel.org/r/20210326070755.304625-1-aneesh.kumar@linux.ibm.com
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version
# < git log --format=%s --max-count=1 53f1d31708f6240e4615b0927df31f182e389e2f
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  ppc64_defconfig
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  help
# make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  olddefconfig
# make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_ppc64_defconfig_powerpc-gcc5
# Build took: 0:03:30.232232