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Mon, 6 Feb 2023 09:08:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=stgolabs.net; s=dreamhost; t=1675703304; bh=zIznFMDI6Lij7FER4Z78PRmQWP5O6fXpz/Om0xIe8N4=; h=Date:From:To:Cc:Subject:Content-Type; b=mXp8B55Ok+VGVQ3wv0CNCIijFteqatu7t72n1gJglNvPTOuL4d9ysY3cRFU1o+CDB dBTfkUddNW9DaaaEP8Hz8mkueG4EQLRNmk35aa9i1AvdaBmQbIgT/bN6Nfi7MruNsS w+3S3BqMeG9kySn/izBNQ7WiXacrbF5UwX/BBVUvVSto+n895E2CUlPdubePVhDW+U 6aBONJrcOsSt4iTjB4AYZvlwP7YNiEnlU2YUCwQoszAuCoIuvfWSheOQiKcqz4SsbH XzFYLo+3c4Lb9sX6PRWWwN5uBJfQOFi5MfflGJPeufCoEoABxWPObHmIEW8ilkbKvR Rk87VjBdNWyBA== Date: Mon, 6 Feb 2023 08:40:56 -0800 From: Davidlohr Bueso To: Gregory Price Cc: Dan Williams , linux-cxl@vger.kernel.org, David Hildenbrand , Kees Cook , stable@vger.kernel.org, Dave Hansen , Michal Hocko , linux-mm@kvack.org, linux-acpi@vger.kernel.org Subject: Re: [PATCH 00/18] CXL RAM and the 'Soft Reserved' => 'System RAM' default Message-ID: <20230206164056.a4ifv3k4juadlazl@offworld> Mail-Followup-To: Gregory Price , Dan Williams , linux-cxl@vger.kernel.org, David Hildenbrand , Kees Cook , stable@vger.kernel.org, Dave Hansen , Michal Hocko , linux-mm@kvack.org, linux-acpi@vger.kernel.org References: <167564534874.847146.5222419648551436750.stgit@dwillia2-xfh.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20220429 Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Mon, 06 Feb 2023, Gregory Price wrote: >On Sun, Feb 05, 2023 at 05:02:29PM -0800, Dan Williams wrote: >> Summary: >> -------- >> >> CXL RAM support allows for the dynamic provisioning of new CXL RAM >> regions, and more routinely, assembling a region from an existing >> configuration established by platform-firmware. The latter is motivated >> by CXL memory RAS (Reliability, Availability and Serviceability) >> support, that requires associating device events with System Physical >> Address ranges and vice versa. >> >> The 'Soft Reserved' policy rework arranges for performance >> differentiated memory like CXL attached DRAM, or high-bandwidth memory, >> to be designated for 'System RAM' by default, rather than the device-dax >> dedicated access mode. That current device-dax default is confusing and >> surprising for the Pareto of users that do not expect memory to be >> quarantined for dedicated access by default. Most users expect all >> 'System RAM'-capable memory to show up in FREE(1). > >Leverage the same QEMU branch, machine, and configuration as my prior >tests, i'm now experiencing a kernel panic on boot. Will debug a bit >in the morning, but here is the stack trace i'm seeing > >Saw this in both 1 and 2 root port configurations I also see it in "regular" pmem setups, and narrowed it down to this change in the last patch: -module_init(cxl_acpi_init); +/* load before dax_hmem sees 'Soft Reserved' CXL ranges */ +subsys_initcall(cxl_acpi_init);