On Thu, 07 Jun 2018 22:58:33 +0530
Mahesh J Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx> wrote:
> From: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx>
>
> During Machine Check interrupt on pseries platform, register r3 points
> RTAS extended event log passed by hypervisor. Since hypervisor uses r3
> to pass pointer to rtas log, it stores the original r3 value at the
> start of the memory (first 8 bytes) pointed by r3. Since hypervisor
> stores this info and rtas log is in BE format, linux should make
> sure to restore r3 value in correct endian format.
>
> Without this patch when MCE handler, after recovery, returns to code that
> that caused the MCE may end up with Data SLB access interrupt for invalid
> address followed by kernel panic or hang.
>
> [ 62.878965] Severe Machine check interrupt [Recovered]
> [ 62.878968] NIP [d00000000ca301b8]: init_module+0x1b8/0x338 [bork_kernel]
> [ 62.878969] Initiator: CPU
> [ 62.878970] Error type: SLB [Multihit]
> [ 62.878971] Effective address: d00000000ca70000
> cpu 0xa: Vector: 380 (Data SLB Access) at [c0000000fc7775b0]
> pc: c0000000009694c0: vsnprintf+0x80/0x480
> lr: c0000000009698e0: vscnprintf+0x20/0x60
> sp: c0000000fc777830
> msr: 8000000002009033
> dar: a803a30c000000d0
> current = 0xc00000000bc9ef00
> paca = 0xc00000001eca5c00 softe: 3 irq_happened: 0x01
> pid = 8860, comm = insmod
> [c0000000fc7778b0] c0000000009698e0 vscnprintf+0x20/0x60
> [c0000000fc7778e0] c00000000016b6c4 vprintk_emit+0xb4/0x4b0
> [c0000000fc777960] c00000000016d40c vprintk_func+0x5c/0xd0
> [c0000000fc777980] c00000000016cbb4 printk+0x38/0x4c
> [c0000000fc7779a0] d00000000ca301c0 init_module+0x1c0/0x338 [bork_kernel]
> [c0000000fc777a40] c00000000000d9c4 do_one_initcall+0x54/0x230
> [c0000000fc777b00] c0000000001b3b74 do_init_module+0x8c/0x248
> [c0000000fc777b90] c0000000001b2478 load_module+0x12b8/0x15b0
> [c0000000fc777d30] c0000000001b29e8 sys_finit_module+0xa8/0x110
> [c0000000fc777e30] c00000000000b204 system_call+0x58/0x6c
> --- Exception: c00 (System Call) at 00007fff8bda0644
> SP (7fffdfbfe980) is in userspace
>
> This patch fixes this issue.
LGTM
Reviewed-by: Nicholas Piggin <npiggin@xxxxxxxxx>
>
> Fixes: a08a53ea4c97 ("powerpc/le: Enable RTAS events support")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx>
> ---
> arch/powerpc/platforms/pseries/ras.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
> index 5e1ef9150182..2edc673be137 100644
> --- a/arch/powerpc/platforms/pseries/ras.c
> +++ b/arch/powerpc/platforms/pseries/ras.c
> @@ -360,7 +360,7 @@ static struct rtas_error_log *fwnmi_get_errinfo(struct pt_regs *regs)
> }
>
> savep = __va(regs->gpr[3]);
> - regs->gpr[3] = savep[0]; /* restore original r3 */
> + regs->gpr[3] = be64_to_cpu(savep[0]); /* restore original r3 */
>
> /* If it isn't an extended log we can use the per cpu 64bit buffer */
> h = (struct rtas_error_log *)&savep[1];
>
