linux-kernel - Re: [PATCH v3 1/1] ppc/crash: Reset spinlocks during crash

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Message-ID: <f967cab2b473406ee6427f40109c85d46b438271.camel@gmail.com>
Date:   Tue, 12 May 2020 00:48:28 -0300
From:   Leonardo Bras <leobras.c@...il.com>
To:     Paul Mackerras <paulus@...abs.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     peterz@...radead.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, Nicholas Piggin <npiggin@...il.com>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Enrico Weigelt <info@...ux.net>
Subject: Re: [PATCH v3 1/1] ppc/crash: Reset spinlocks during crash

Hello Paul, thanks for the reply!

On Thu, 2020-04-09 at 10:27 +1000, Paul Mackerras wrote:
> On Wed, Apr 08, 2020 at 10:21:29PM +1000, Michael Ellerman wrote:
> > We should be able to just allocate the rtas_args on the stack, it's only
> > ~80 odd bytes. And then we can use rtas_call_unlocked() which doesn't
> > take the global lock.
> 
> Do we instantiate a 64-bit RTAS these days, or is it still 32-bit?

According to LoPAR, we can use instantiate-rtas or instantiate-rtas-64. 
It looks like we do instantiate-rtas today (grep pointed only to
prom_instantiate_rtas()).

> In the old days we had to make sure the RTAS argument buffer was
> below the 4GB point.  If that's still necessary then perhaps putting
> rtas_args inside the PACA would be the way to go.

Yes, we still need to make sure of this. I will study more about PACA
and try to implement that way.

Best regards,
Leonardo Bras

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