Subject: Re: [PATCH v4 04/16] powerpc/64s/exceptions: machine check reconcile irq state

From: Michael Ellerman <[email-masked]>
Date: Fri, 08 May 2020 23:39:03 +1000

Nicholas Piggin <[email-masked]> writes:

> pseries fwnmi machine check code pops the soft-irq checks in rtas_call
> (after the previous patch to remove rtas_token from this call path).
             ^
             I changed this to "next" which I think is what you meant?

cheers

> Rather than play whack a mole with these and forever having fragile
> code, it seems better to have the early machine check handler perform
> the same kind of reconcile as the other NMI interrupts.
>
>   WARNING: CPU: 0 PID: 493 at arch/powerpc/kernel/irq.c:343
>   CPU: 0 PID: 493 Comm: a Tainted: G        W
>   NIP:  c00000000001ed2c LR: c000000000042c40 CTR: 0000000000000000
>   REGS: c0000001fffd38b0 TRAP: 0700   Tainted: G        W
>   MSR:  8000000000021003 <SF,ME,RI,LE>  CR: 28000488  XER: 00000000
>   CFAR: c00000000001ec90 IRQMASK: 0
>   GPR00: c000000000043820 c0000001fffd3b40 c0000000012ba300 0000000000000000
>   GPR04: 0000000048000488 0000000000000000 0000000000000000 00000000deadbeef
>   GPR08: 0000000000000080 0000000000000000 0000000000000000 0000000000001001
>   GPR12: 0000000000000000 c0000000014a0000 0000000000000000 0000000000000000
>   GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>   GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>   GPR24: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>   GPR28: 0000000000000000 0000000000000001 c000000001360810 0000000000000000
>   NIP [c00000000001ed2c] arch_local_irq_restore.part.0+0xac/0x100
>   LR [c000000000042c40] unlock_rtas+0x30/0x90
>   Call Trace:
>   [c0000001fffd3b40] [c000000001360810] 0xc000000001360810 (unreliable)
>   [c0000001fffd3b60] [c000000000043820] rtas_call+0x1c0/0x280
>   [c0000001fffd3bb0] [c0000000000dc328] fwnmi_release_errinfo+0x38/0x70
>   [c0000001fffd3c10] [c0000000000dcd8c] pseries_machine_check_realmode+0x1dc/0x540
>   [c0000001fffd3cd0] [c00000000003fe04] machine_check_early+0x54/0x70
>   [c0000001fffd3d00] [c000000000008384] machine_check_early_common+0x134/0x1f0
>   --- interrupt: 200 at 0x13f1307c8
>       LR = 0x7fff888b8528
>   Instruction dump:
>   60000000 7d2000a6 71298000 41820068 39200002 7d210164 4bffff9c 60000000
>   60000000 7d2000a6 71298000 4c820020 <0fe00000> 4e800020 60000000 60000000
>
> Signed-off-by: Nicholas Piggin <[email-masked]>
> ---
>  arch/powerpc/kernel/exceptions-64s.S | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> index a42b73efb1a9..072772803b7c 100644
> --- a/arch/powerpc/kernel/exceptions-64s.S
> +++ b/arch/powerpc/kernel/exceptions-64s.S
> @@ -1116,11 +1116,30 @@ END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
>  	li	r10,MSR_RI
>  	mtmsrd	r10,1
>  
> +	/*
> +	 * Set IRQS_ALL_DISABLED and save PACAIRQHAPPENED (see
> +	 * system_reset_common)
> +	 */
> +	li	r10,IRQS_ALL_DISABLED
> +	stb	r10,PACAIRQSOFTMASK(r13)
> +	lbz	r10,PACAIRQHAPPENED(r13)
> +	std	r10,RESULT(r1)
> +	ori	r10,r10,PACA_IRQ_HARD_DIS
> +	stb	r10,PACAIRQHAPPENED(r13)
> +
>  	addi	r3,r1,STACK_FRAME_OVERHEAD
>  	bl	machine_check_early
>  	std	r3,RESULT(r1)	/* Save result */
>  	ld	r12,_MSR(r1)
>  
> +	/*
> +	 * Restore soft mask settings.
> +	 */
> +	ld	r10,RESULT(r1)
> +	stb	r10,PACAIRQHAPPENED(r13)
> +	ld	r10,SOFTE(r1)
> +	stb	r10,PACAIRQSOFTMASK(r13)
> +
>  #ifdef CONFIG_PPC_P7_NAP
>  	/*
>  	 * Check if thread was in power saving mode. We come here when any
> -- 
> 2.23.0