linux-kernel - Re: [v2] powernv:idle: Fix bug due to labeling ambiguity in power_enter

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Date:   Wed,  8 Mar 2017 18:25:54 +1100 (AEDT)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Neuling <mikey@...ling.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        "Shreyas B. Prabhu" <shreyasbp@...il.com>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        Balbir Singh <bsingharora@...il.com>,
        Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>,
        Anton Blanchard <anton@...ba.org>
Cc:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [v2] powernv:idle: Fix bug due to labeling ambiguity in power_enter_stop

On Mon, 2017-02-27 at 05:40:07 UTC, "Gautham R. Shenoy" wrote:
> From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
> 
> Commit 09206b600c76 ("powernv: Pass PSSCR value and mask to
> power9_idle_stop") added additional code in power_enter_stop() to
> distinguish between stop requests whose PSSCR had ESL=EC=1 from those
> which did not. When ESL=EC=1, we do a forward-jump to a location
> labelled by "1", which had the code to handle the ESL=EC=1 case.
> 
> Unforunately just a couple of instructions before this label, is the
> macro IDLE_STATE_ENTER_SEQ() which also has a label "1" in its
> expansion.
> 
> As a result, the current code can result in directly executing stop
> instruction for deep stop requests with PSSCR ESL=EC=1, without saving
> the hypervisor state.
> 
> Fix this BUG by labeling the location that handles ESL=EC=1 case with
> a more descriptive label ".Lhandle_esl_ec_set" (local label suggestion
> a la .Lxx from Anton Blanchard).
> 
> While at it, rename the label "2" labelling the location of the code
> handling entry into deep stop states with ".Lhandle_deep_stop".
> 
> For a good measure, change the label in IDLE_STATE_ENTER_SEQ() macro
> to an not-so commonly used value in order to avoid similar mishaps in
> the future.
> 
> Fixes: 09206b600c76 ("powernv: Pass PSSCR value and mask to
> power9_idle_stop")
> 
> Cc: Michael Neuling <mikey@...ling.org>
> Cc: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/424f8acd328a111319ae30bf384e5d

cheers