From: Dave Jiang Subject: Re: Help trying to use /dev/pmem for dax debugging? Date: Tue, 31 Jul 2018 13:27:15 -0700 Message-ID: <30247efc-88f8-3e0b-fcd8-83801be5f041@intel.com> References: <20180730235312.GA5089@thunk.org> <20180731193642.GA3473@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Cc: linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Matthew Wilcox , linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org To: Ross Zwisler , "Theodore Y. Ts'o" Return-path: In-Reply-To: <20180731193642.GA3473-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" List-Id: linux-ext4.vger.kernel.org On 7/31/2018 12:36 PM, Ross Zwisler wrote: > On Mon, Jul 30, 2018 at 07:53:12PM -0400, Theodore Y. Ts'o wrote: >> In newer kernels, it looks like you can't use /dev/pmem0 for DAX >> unless it's marked as being DAX capable. This appears to require >> CONFIG_NVDIMM_PFN. But when I tried to build a kernel with that >> configured, I get the following BUG: >> >> [ 0.000000] Linux version 4.18.0-rc4-xfstests-00031-g7c2d77aa7d80 (tytso@cwcc) (gcc version 7.3.0 (Debian 7.3.0-27)) #460 SMP Mon Jul 30 19:38:44 EDT 2018 >> [ 0.000000] Command line: systemd.show_status=auto systemd.log_level=crit root=/dev/vda console=ttyS0,115200 cmd=maint fstesttz=America/New_York fstesttyp=ext4 fstestapi=1.4 memmap=4G!9G memmap=9G!14G > Hey Ted, > > You're using the memmap kernel command line parameter to reserve normal > memory to be treated as normal memory, but you've also got kernel address > randomization turned on in your kernel config: > > CONFIG_RANDOMIZE_BASE=y > CONFIG_RANDOMIZE_MEMORY=y > > You need to turn these off for the memmap kernel command line parameter, else > the memory we're using could overlap with addresses used for other things. I believe this issue was fixed a while back. Although we probably can see if that is the issue or something else. > > Once that is off you probably want to double check that the addresses you're > reserving are marked as 'usable' in the e820 table. Gory details here, sorry > for the huge link: > > https://nvdimm.wiki.kernel.org/how_to_choose_the_correct_memmap_kernel_parameter_for_pmem_on_your_system > > - Ross > _______________________________________________ > Linux-nvdimm mailing list > Linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org > https://lists.01.org/mailman/listinfo/linux-nvdimm