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Date:   Mon, 19 Oct 2020 11:37:14 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Ira Weiny <ira.weiny@intel.com>
Cc:     Dave Hansen <dave.hansen@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>,
        Fenghua Yu <fenghua.yu@intel.com>, x86@kernel.org,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH RFC V3 4/9] x86/pks: Preserve the PKRS MSR on context
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On Fri, Oct 16, 2020 at 10:14:10PM -0700, Ira Weiny wrote:
> > so it either needs to
> > explicitly do so, or have an assertion that preemption is indeed
> > disabled.
> 
> However, I don't think I understand clearly.  Doesn't [get|put]_cpu_ptr()
> handle the preempt_disable() for us? 

It does.

> Is it not sufficient to rely on that?

It is.

> Dave's comment seems to be the opposite where we need to eliminate preempt
> disable before calling write_pkrs().
> 
> FWIW I think I'm mistaken in my response to Dave regarding the
> preempt_disable() in pks_update_protection().

Dave's concern is that we're calling with with preemption already
disabled so disabling it again is superfluous.