From: Nathan Lynch <nathanl@linux.ibm.com>
To: Leonardo Bras <leobras.c@gmail.com>
Cc: Leonardo Bras <leobras.c@gmail.com>,
"Gautham R. Shenoy" <ego@linux.vnet.ibm.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, Nicholas Piggin <npiggin@gmail.com>,
Paul Mackerras <paulus@samba.org>, Nadav Amit <namit@vmware.com>,
Thomas Gleixner <tglx@linutronix.de>,
linuxppc-dev@lists.ozlabs.org,
Allison Randal <allison@lohutok.net>
Subject: Re: [PATCH v3 2/2] powerpc/rtas: Implement reentrant rtas call
Date: Thu, 14 May 2020 13:58:18 -0500 [thread overview]
Message-ID: <878shu2vjp.fsf@linux.ibm.com> (raw)
In-Reply-To: <20200514011245.127174-3-leobras.c@gmail.com>
Hi,
Leonardo Bras <leobras.c@gmail.com> writes:
> +/**
> + * rtas_call_reentrant() - Used for reentrant rtas calls
> + * @token: Token for desired reentrant RTAS call
> + * @nargs: Number of Input Parameters
> + * @nret: Number of Output Parameters
> + * @outputs: Array of outputs
> + * @...: Inputs for desired RTAS call
> + *
> + * According to LoPAR documentation, only "ibm,int-on", "ibm,int-off",
> + * "ibm,get-xive" and "ibm,set-xive" are currently reentrant.
> + * Reentrant calls need their own rtas_args buffer, so not using rtas.args, but
> + * PACA one instead.
> + *
> + * Return: -1 on error,
> + * First output value of RTAS call if (nret > 0),
> + * 0 otherwise,
> + */
> +
> +int rtas_call_reentrant(int token, int nargs, int nret, int *outputs, ...)
> +{
> + va_list list;
> + struct rtas_args *args;
> + int i;
> +
> + if (!rtas.entry || token == RTAS_UNKNOWN_SERVICE)
> + return -1;
> +
> + /* We use the per-cpu (PACA) rtas args buffer */
> + args = &local_paca->reentrant_args;
> +
> + va_start(list, outputs);
> + va_rtas_call_unlocked(args, token, nargs, nret, list);
> + va_end(list);
> +
> + if (nret > 1 && outputs)
> + for (i = 0; i < nret - 1; ++i)
> + outputs[i] = be32_to_cpu(args->rets[i + 1]);
Doesn't this need to be more careful about preemption and exceptions?
I.e. the args structure in the paca needs to be protected from
concurrent use somehow, like any per-cpu data structure.
local_irq_save/restore while accessing local_paca->reentrant_args here
would be sufficient I think?
next prev parent reply other threads:[~2020-05-14 19:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-14 1:12 [PATCH v3 0/2] Implement reentrant rtas call Leonardo Bras
2020-05-14 1:12 ` [PATCH v3 1/2] powerpc/rtas: Move type/struct definitions from rtas.h into rtas-types.h Leonardo Bras
2020-05-14 1:12 ` [PATCH v3 2/2] powerpc/rtas: Implement reentrant rtas call Leonardo Bras
2020-05-14 18:58 ` Nathan Lynch [this message]
2020-05-14 23:28 ` Leonardo Bras
2020-05-15 0:00 ` Leonardo Bras
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