linux-kernel - Re: [RESEND][PATCH] powerpc/powernv : Save/Restore SPRG3 on entry/exit from stop.

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Date:   Wed, 18 Jul 2018 09:24:19 +1000
From:   Michael Neuling <mikey@...ling.org>
To:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Florian Weimer <fweimer@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>
Subject: Re: [RESEND][PATCH] powerpc/powernv : Save/Restore SPRG3 on
 entry/exit from stop.


>  	DEFINE(PPC_DBELL_SERVER, PPC_DBELL_SERVER);
> diff --git a/arch/powerpc/kernel/idle_book3s.S
> b/arch/powerpc/kernel/idle_book3s.S
> index d85d551..5069d42 100644
> --- a/arch/powerpc/kernel/idle_book3s.S
> +++ b/arch/powerpc/kernel/idle_book3s.S
> @@ -120,6 +120,9 @@ power9_save_additional_sprs:
>  	mfspr	r4, SPRN_MMCR2
>  	std	r3, STOP_MMCR1(r13)
>  	std	r4, STOP_MMCR2(r13)
> +
> +	mfspr	r3, SPRN_SPRG3
> +	std	r3, STOP_SPRG3(r13)

We don't need to save it.  Just restore it from paca->sprg_vdso which should
never change.

How can we do better at catching these missing SPRGs? 

We missed this one and looking at c1b25a17d249 we missed the AMOR a couple of
months back. I'd rather we had some systematic way of finding the ones we are
missing, rather than playing wake-a-mole.

Mikey 

>  	blr
>  
>  power9_restore_additional_sprs:
> @@ -144,7 +147,9 @@ power9_restore_additional_sprs:
>  	mtspr	SPRN_MMCR1, r4
>  
>  	ld	r3, STOP_MMCR2(r13)
> +	ld	r4, STOP_SPRG3(r13)
>  	mtspr	SPRN_MMCR2, r3
> +	mtspr	SPRN_SPRG3, r4
>  	blr
>  
>  /*