tree dda61b3752026feabb33ae8769ca034badabc0a5
parent 5da5f47e6c65eda83e5433bd905c4df03be98596
author Ganesh Goudar <ganeshgr@linux.ibm.com> 1586365784 +0530
committer David Gibson <david@gibson.dropbear.id.au> 1587083909 +1000

target/ppc: Fix wrong interpretation of the disposition flag.

Bitwise AND with kvm_run->flags to evaluate if we recovered from
MCE or not is not correct, As disposition in kvm_run->flags is a
two-bit integer value and not a bit map, So check for equality
instead of bitwise AND.

Without the fix qemu treats any unrecoverable mce error as recoverable
and ends up in a mce loop inside the guest, Below are the MCE logs before
and after the fix.

Before fix:

[   66.775757] MCE: CPU0: Initiator CPU
[   66.775891] MCE: CPU0: Unknown
[   66.776587] MCE: CPU0: machine check (Harmless) Host UE Indeterminate [Recovered]
[   66.776857] MCE: CPU0: NIP: [c0080000000e00b8] mcetest_tlbie+0xb0/0x128 [mcetest_tlbie]

After fix:

[ 20.650577] CPU: 0 PID: 1415 Comm: insmod Tainted: G M O 5.6.0-fwnmi-arv+ #11
[ 20.650618] NIP: c0080000023a00e8 LR: c0080000023a00d8 CTR: c000000000021fe0
[ 20.650660] REGS: c0000001fffd3d70 TRAP: 0200 Tainted: G M O (5.6.0-fwnmi-arv+)
[ 20.650708] MSR: 8000000002a0b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 42000222 XER: 20040000
[ 20.650758] CFAR: c00000000000b940 DAR: c0080000025e00e0 DSISR: 00000200 IRQMASK: 0
[ 20.650758] GPR00: c0080000023a00d8 c0000001fddd79a0 c0080000023a8500 0000000000000039
[ 20.650758] GPR04: 0000000000000001 0000000000000000 0000000000000000 0000000000000007
[ 20.650758] GPR08: 0000000000000007 c0080000025e00e0 0000000000000000 00000000000000f7
[ 20.650758] GPR12: 0000000000000000 c000000001900000 c00000000101f398 c0080000025c052f
[ 20.650758] GPR16: 00000000000003a8 c0080000025c0000 c0000001fddd7d70 c0000000015b7940
[ 20.650758] GPR20: 000000000000fff1 c000000000f72c28 c0080000025a0988 0000000000000000
[ 20.650758] GPR24: 0000000000000100 c0080000023a05d0 c0000000001f1d70 0000000000000000
[ 20.650758] GPR28: c0000001fde20000 c0000001fd02b2e0 c0080000023a0000 c0080000025e0000
[ 20.651178] NIP [c0080000023a00e8] mcetest_tlbie+0xe8/0xf0 [mcetest_tlbie]
[ 20.651220] LR [c0080000023a00d8] mcetest_tlbie+0xd8/0xf0 [mcetest_tlbie]
[ 20.651262] Call Trace:
[ 20.651280] [c0000001fddd79a0] [c0080000023a00d8] mcetest_tlbie+0xd8/0xf0 [mcetest_tlbie] (unreliable)
[ 20.651340] [c0000001fddd7a10] [c00000000001091c] do_one_initcall+0x6c/0x2c0
[ 20.651390] [c0000001fddd7af0] [c0000000001f7998] do_init_module+0x90/0x298
[ 20.651433] [c0000001fddd7b80] [c0000000001f61a8] load_module+0x1f58/0x27a0
[ 20.651476] [c0000001fddd7d40] [c0000000001f6c70] __do_sys_finit_module+0xe0/0x100
[ 20.651526] [c0000001fddd7e20] [c00000000000b9d0] system_call+0x5c/0x68
[ 20.651567] Instruction dump:
[ 20.651594] e8410018 3c620000 e8638020 480000cd e8410018 3c620000 e8638028 480000bd
[ 20.651646] e8410018 7be904e4 39400000 612900e0 <7d434a64> 4bffff74 3c4c0001 38428410
[ 20.651699] ---[ end trace 4c40897f016b4340 ]---
[ 20.653310]
Bus error
[ 20.655575] MCE: CPU0: machine check (Harmless) Host UE Indeterminate [Not recovered]
[ 20.655575] MCE: CPU0: NIP: [c0080000023a00e8] mcetest_tlbie+0xe8/0xf0 [mcetest_tlbie]
[ 20.655576] MCE: CPU0: Initiator CPU
[ 20.655576] MCE: CPU0: Unknown

Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
Message-Id: <20200408170944.16003-1-ganeshgr@linux.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>