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From:   Jeff Moyer <jmoyer@redhat.com>
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     linux-nvdimm <linux-nvdimm@lists.01.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/3] libnvdimm/security: Tighten scope of nvdimm->busy vs security operations
References: <156583201347.2815870.4687949334637966672.stgit@dwillia2-desk3.amr.corp.intel.com>
        <156583202386.2815870.16611751329252858110.stgit@dwillia2-desk3.amr.corp.intel.com>
        <x49zhk8bzuh.fsf@segfault.boston.devel.redhat.com>
        <CAPcyv4iPBO9atdr_LdHNt=tCgjh-j_HyKXaCdUkWxb_J7OCcxg@mail.gmail.com>
Date:   Mon, 19 Aug 2019 10:32:22 -0400
In-Reply-To: <CAPcyv4iPBO9atdr_LdHNt=tCgjh-j_HyKXaCdUkWxb_J7OCcxg@mail.gmail.com>
        (Dan Williams's message of "Fri, 16 Aug 2019 14:02:19 -0700")
Message-ID: <x49d0h1usy1.fsf@segfault.boston.devel.redhat.com>
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Dan Williams <dan.j.williams@intel.com> writes:

> On Fri, Aug 16, 2019 at 1:49 PM Jeff Moyer <jmoyer@redhat.com> wrote:
>>
>> Dan Williams <dan.j.williams@intel.com> writes:
>>
>> > The blanket blocking of all security operations while the DIMM is in
>> > active use in a region is too restrictive. The only security operations
>> > that need to be aware of the ->busy state are those that mutate the
>> > state of data, i.e. erase and overwrite.
>> >
>> > Refactor the ->busy checks to be applied at the entry common entry point
>> > in __security_store() rather than each of the helper routines.
>>
>> I'm not sure this buys you much.  Did you test this on actual hardware
>> to make sure your assumptions are correct?  I guess the worst case is we
>> get an "invalid security state" error back from the firmware....
>>
>> Still, what's the motivation for this?
>
> The motivation was when I went to test setting the frozen state and
> found that it complained about the DIMM being active. There's nothing
> wrong with freezing security while the DIMM is mapped. ...but then I
> somehow managed to write this generalized commit message that left out
> the explicit failure I was worried about. Yes, moved too fast, but the
> motivation is "allow freeze while active" and centralize the ->busy
> check so it's just one function to review that common constraint.

OK, thanks for the info.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>