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From:   Sven Schnelle <svens@linux.ibm.com>
To:     Heiko Carstens <hca@linux.ibm.com>
Cc:     "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Jiri Kosina <jikos@kernel.org>,
        Joe Lawrence <joe.lawrence@redhat.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Miroslav Benes <mbenes@suse.cz>,
        Ingo Molnar <mingo@redhat.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "live-patching@vger.kernel.org" <live-patching@vger.kernel.org>
Subject: Re: [PATCH v2 09/13] powerpc/ftrace: Implement
 CONFIG_DYNAMIC_FTRACE_WITH_ARGS
References: <cover.1640017960.git.christophe.leroy@csgroup.eu>
        <5831f711a778fcd6eb51eb5898f1faae4378b35b.1640017960.git.christophe.leroy@csgroup.eu>
        <1644852011.qg7ud9elo2.naveen@linux.ibm.com>
        <1b28f52a-f8b7-6b5c-e726-feac4123517d@csgroup.eu>
        <875ypgo0f3.fsf@mpe.ellerman.id.au>
        <1644930705.g64na2kgvd.naveen@linux.ibm.com>
        <6dc50f09-4d14-afa2-d2a1-34b72b880edf@csgroup.eu>
        <5c7b5334-6071-f131-a509-9a49ca3d628c@csgroup.eu>
        <1644941712.lqdstzo09z.naveen@linux.ibm.com> <Ygz2Upu+5NiEAsDT@osiris>
Date:   Wed, 16 Feb 2022 14:27:09 +0100
In-Reply-To: <Ygz2Upu+5NiEAsDT@osiris> (Heiko Carstens's message of "Wed, 16
        Feb 2022 14:04:18 +0100")
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Heiko Carstens <hca@linux.ibm.com> writes:

> So, the in both variants s390 provides nearly identical data. The only
> difference is that for FL_SAVE_REGS the program status word mask is
> missing; therefore it is not possible to figure out the condition code
> or if interrupts were enabled/disabled.
>
> Vasily, Sven, I think we have two options here:
>
> - don't provide sane psw mask contents at all and say (again) that
>   ptregs contents are identical
>
> - provide (finally) a full psw mask contents using epsw, and indicate
>   validity with a flags bit in pt_regs
>
> I would vote for the second option, even though epsw is slow. But this
> is about the third or fourth time this came up in different
> contexts. So I'd guess we should go for the slow but complete
> solution. Opinions?

Given that this only affects ftrace_regs_caller, i would also vote for the
second option.