On Wed, 28 Jun 2017 06:46:49 +0530
Akshay Adiga <akshay.ad...@linux.vnet.ibm.com> wrote:
> pnv_wakeup_noloss expects R12 to contain SRR1 value to determine if
> the wakeup reason is an HMI in CHECK_HMI_INTERRUPT.
>
> When we wakeup with ESL=0, SRR1 will not contain the wakeup reason, so
> there is no point setting R12 to SRR1.
>
> However, we don't set R12 at all and R12 contains garbage, and still
> being used to check HMI assuming that it had SRR1. causing the
> OPAL msglog to be filled with the following print:
> HMI: Received HMI interrupt: HMER = 0x0040000000000000
>
> This patch clears R12 after waking up from stop with ESL=EC=0, so that
> we don't accidentally enter the HMI handler in pnv_wakeup_noloss if
> the R12[42:45] corresponds to HMI as wakeup reason.
>
> Bug existed prior to "commit 9d29250136f6 ("powerpc/64s/idle: Avoid SRR
> usage in idle sleep/wake paths") but was never hit in practice
>
> Signed-off-by: Akshay Adiga <akshay.ad...@linux.vnet.ibm.com>
> Fixes: 9d29250136f6 ("powerpc/64s/idle: Avoid SRR usage in idle
> sleep/wake paths")
Thanks guys, appreciate you finding and fixing my bug :)
I think this looks like the best fix. Really minor nitpick but you
could adjust the line widths on the comment slightly (mpe might do
that when merging).
Reviewed-by: Nicholas Piggin <npig...@gmail.com>
> ---
> arch/powerpc/kernel/idle_book3s.S | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/arch/powerpc/kernel/idle_book3s.S
> b/arch/powerpc/kernel/idle_book3s.S
> index 1ea14b9..34794fd 100644
> --- a/arch/powerpc/kernel/idle_book3s.S
> +++ b/arch/powerpc/kernel/idle_book3s.S
> @@ -256,6 +256,21 @@ power_enter_stop:
> bne .Lhandle_esl_ec_set
> IDLE_STATE_ENTER_SEQ(PPC_STOP)
> li r3,0 /* Since we didn't lose state, return 0 */
> + /*
> + * pnv_wakeup_noloss expects R12 to contain SRR1 value
> + * to determine if the wakeup reason is an HMI in
> + * CHECK_HMI_INTERRUPT.
> + *
> + * However, when we wakeup with ESL=0,
> + * SRR1 will not contain the wakeup reason,
> + * so there is no point setting R12 to SRR1.
> + *
> + * Further, we clear R12 here, so that we
> + * don't accidentally enter the HMI
> + * in pnv_wakeup_noloss if the
> + * R12[42:45] == WAKE_HMI.
> + */
> + li r12, 0
> b pnv_wakeup_noloss
>
> .Lhandle_esl_ec_set:
