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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Mon, 15 Jun 2020 12:06:11 -0700
Message-ID: <CAPcyv4iA+21rrwfZ9SdV903TiTo9sA7KfrKVQfLOO-612uanpQ@mail.gmail.com>
Subject: Re: [RFT][PATCH 2/3] ACPICA: Remove unused memory mappings on
 interpreter exit
To:     "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc:     "Kaneda, Erik" <erik.kaneda@intel.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        "Wysocki, Rafael J" <rafael.j.wysocki@intel.com>,
        Len Brown <lenb@kernel.org>, Borislav Petkov <bp@alien8.de>,
        "Weiny, Ira" <ira.weiny@intel.com>,
        James Morse <james.morse@arm.com>,
        Myron Stowe <myron.stowe@redhat.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
        "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
        "Moore, Robert" <robert.moore@intel.com>
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On Sat, Jun 13, 2020 at 12:29 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
[,,]
> > While I agree that this is still somewhat suboptimal, improving this
> > would require more changes in the OSL code.
>
> After writing the above I started to think about the extra changes needed
> to improve that and I realized that it would take making the OS layer
> support deferred memory unmapping, such that the unused mappings would be
> queued up for later removal and then released in one go at a suitable time.
>
> However, that would be sufficient to address the issue addressed by this
> series, because the deferred unmapping could be used in
> acpi_ev_system_memory_region_setup() right away and that would be a much
> simpler change than the one made in patch [1/3].
>
> So I went ahead and implemented this and the result is there in the
> acpica-osl branch in my tree, but it hasn't been built yet, so caveat
> emptor.  Anyway, please feel free to have a look at it still.

I'll have a look. However, I was just about to build a test kernel for
the original reporter of this problem with this patch set. Do you want
test feedback on that branch, or this set as is?