linux-kernel - Re: [PATCH 3/3] powernv:idle: Set LPCR

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Date:   Thu, 13 Apr 2017 09:28:33 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michael Neuling <mikey@...ling.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "Shreyas B. Prabhu" <shreyasbp@...il.com>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Anton Blanchard <anton@...ba.org>,
        Balbir Singh <bsingharora@...il.com>,
        Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Mahesh J Salgaonkar <mahesh@...ux.vnet.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
Subject: Re: [PATCH 3/3] powernv:idle: Set LPCR_UPRT on wakeup from deep-stop

"Gautham R. Shenoy" <ego@...ux.vnet.ibm.com> writes:

> From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
>
> On wakeup from a deep-stop used for CPU-Hotplug, we invoke
> cur_cpu_spec->cpu_restore() which would set sane default values to
> various SPRs including LPCR.
>
> On POWER9, the cpu_restore_power9() call would would restore LPCR to a
> sane value that is set at early boot time, thereby clearing LPCR_UPRT.
>
> However, LPCR_UPRT is required to be set if we are running in Radix
> mode. If this is not set we will end up with a crash when we enable
> IR,DR.
>
> To fix this, after returning from cur_cpu_spec->cpu_restore() in the
> idle exit path, set LPCR_UPRT if we are running in Radix mode.
>
> Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
> ---
>  arch/powerpc/kernel/idle_book3s.S | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
> index 6a9bd28..39a9b63 100644
> --- a/arch/powerpc/kernel/idle_book3s.S
> +++ b/arch/powerpc/kernel/idle_book3s.S
> @@ -804,6 +804,19 @@ no_segments:
>  #endif
>  	mtctr	r12
>  	bctrl
> +/*
> + * cur_cpu_spec->cpu_restore would restore LPCR to a
> + * sane value that is set at early boot time,
> + * thereby clearing LPCR_UPRT.
> + * LPCR_UPRT is required if we are running in Radix mode.
> + * Set it here if that be the case.
> + */
> +BEGIN_MMU_FTR_SECTION
> +	mfspr	r3, SPRN_LPCR
> +	LOAD_REG_IMMEDIATE(r4, LPCR_UPRT)
> +	or	r3, r3, r4
> +	mtspr	SPRN_LPCR, r3
> +END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_RADIX)

What about LPCR_HR ?

>  
>  hypervisor_state_restored:
>  
> -- 
> 1.9.4

-aneesh