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Date:   Fri, 28 Sep 2018 13:59:07 -0700
From:   Andi Kleen <ak@linux.intel.com>
To:     Jann Horn <jannh@google.com>
Cc:     Mark Rutland <mark.rutland@arm.com>,
        Thomas Gleixner <tglx@linutronix.de>, tursulin@ursulin.net,
        kernel list <linux-kernel@vger.kernel.org>,
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        the arch/x86 maintainers <x86@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>, acme@kernel.org,
        alexander.shishkin@linux.intel.com, jolsa@redhat.com,
        namhyung@kernel.org, maddy@linux.vnet.ibm.com,
        alexey.budankov@linux.intel.com, Kees Cook <keescook@chromium.org>
Subject: Re: [RFC 0/5] perf: Per PMU access controls (paranoid setting)
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> > This new file descriptor argument doesn't exist today so it would
> > need to create a new system call with more arguments
> 
> Is that true? The first argument is a pointer to a struct that
> contains its own size, so it can be expanded without an ABI break. I
> don't see any reason why you couldn't cram more stuff in there.

You're right we could put the fd into the perf_event, but the following is
still true:

> > Obviously we would need to keep the old system call around
> > for compability, so you would need to worry about this
> > interaction in any case!
> >
> > So tying it together doesn't make any sense, because
> > the problem has to be solved separately anyways.


-Andi