On 5/1/19 7:14 AM, Michael Ellerman wrote:
"Aneesh Kumar K.V" <aneesh.ku...@linux.ibm.com> writes:
This patch fixes the below crash by making sure we touch the subpage protection
related structures only if we know they are allocated on the platform. With
radix translation we don't allocate hash context at all and trying to access
subpage_prot_table results in
Faulting instruction address: 0xc00000000008bdb4
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Radix MMU=Hash SMP NR_CPUS=2048 NUMA PowerNV
....
NIP [c00000000008bdb4] sys_subpage_prot+0x74/0x590
LR [c00000000000b688] system_call+0x5c/0x70
Call Trace:
[c00020002c6b7d30] [c00020002c6b7d90] 0xc00020002c6b7d90 (unreliable)
[c00020002c6b7e20] [c00000000000b688] system_call+0x5c/0x70
Instruction dump:
fb61ffd8 fb81ffe0 fba1ffe8 fbc1fff0 fbe1fff8 f821ff11 e92d1178 f9210068
39200000 e92d0968 ebe90630 e93f03e8 <eb891038> 60000000 3860fffe e9410068
We also move the subpage_prot_table with mmp_sem held to avoid racec
between two parallel subpage_prot syscall.
Reported-by: Sachin Sant <sach...@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
Presumably it was:
701101865f5d ("powerpc/mm: Reduce memory usage for mm_context_t for radix")
That caused the breakage?
that is correct. Sorry i missed the Fixes: line.
-aneesh
