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Date:   Sat, 17 Jul 2021 14:54:06 -0500
From:   "Sierra Guiza, Alejandro (Alex)" <>
To:     Felix Kuehling <>,
        "Theodore Y. Ts'o" <>
Subject: Re: [PATCH v3 0/8] Support DEVICE_GENERIC memory in migrate_vma_*

On 7/16/2021 5:14 PM, Felix Kuehling wrote:
> Am 2021-07-16 um 11:07 a.m. schrieb Theodore Y. Ts'o:
>> On Wed, Jun 23, 2021 at 05:49:55PM -0400, Felix Kuehling wrote:
>>> I can think of two ways to test the changes for MEMORY_DEVICE_GENERIC in
>>> this patch series in a way that is reproducible without special hardware and
>>> firmware:
>>> For the reference counting changes we could use the dax driver with hmem and
>>> use efi_fake_mem on the kernel command line to create some DEVICE_GENERIC
>>> pages. I'm open to suggestions for good user mode tests to exercise dax
>>> functionality on this type of memory.
>> Sorry for the thread necromancy, but now that the merge window is
>> past....
> No worries. Alejandro should have a new version of this series in a few
> days, with updates to hmm_test and some fixes.

V4 patch series have been sent for review.

Alex Sierra

>> Today I test ext4's dax support, without having any $$$ DAX hardware,
>> by using the kernel command line "memmap=4G!9G:memmap=9G!14G" which
>> reserves memory so that creates two pmem device and then I run
>> xfstests with DAX enabled using qemu or using a Google Compute Engine
>> VM, using TEST_DEV=/dev/pmem0 and SCRATCH_DEV=/dev/pmem1.
>> If you can give me a recipe for what kernel configs I should enable,
>> and what magic kernel command line arguments to use, then I'd be able
>> to test your patch set with ext4.
> That would be great!
> Regarding kernel config options, it should be the same as what you're
> using for DAX testing today. We're not changing or adding any Kconfig
> options. But let me take a stab:
> DEVICE_PRIVATE (maybe not needed for your test)
> I'm not sure what you're looking for in terms of kernel command line,
> other than the memmap options you already found. There are some more
> options to run hmm_test with fake SPM (DEVICE_GENERIC) memory, but we're
> already running that ourselves. That will also be in the next revision
> of this patch series.

In order to run hmm test with generic device type enabled, set the 

kernel config:

Kernel parameters to fake SP memory. The addresses set here are based on 
my system's usable memory enumerated by BIOS-e820 at boot. The test 
requires two SP devices of at least 256MB.

To run the hmm_test in generic device type pass the SP addresses to the 
sh script.
sudo ./ smoke 0x100000000 0x140000000

> If you can run your xfstests with DAX on top of this patch series, that
> would be very helpful. That's to make sure the ZONE_DEVICE page refcount
> changes don't break DAX.
> Regards,
>    Felix
>> Cheers,
>> 						- Ted

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