linux-ext4 - Re: [PATCH v3 0/8] Support DEVICE_GENERIC memory in migrate_vma

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Date:   Fri, 23 Jul 2021 17:46:30 -0500
From:   "Sierra Guiza, Alejandro (Alex)" <alex.sierra@....com>
To:     Felix Kuehling <felix.kuehling@....com>,
        "Theodore Y. Ts'o" <tytso@....edu>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        rcampbell@...dia.com, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, hch@....de, jgg@...dia.com,
        jglisse@...hat.com
Subject: Re: [PATCH v3 0/8] Support DEVICE_GENERIC memory in migrate_vma_*


On 7/17/2021 2:54 PM, Sierra Guiza, Alejandro (Alex) wrote:
>
> 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.
> https://marc.info/?l=dri-devel&m=162654971618911&w=2
>
> Regards,
> 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:
>>
>> ZONE_DEVICE
>> HMM_MIRROR
>> MMU_NOTIFIER
>> DEVICE_PRIVATE (maybe not needed for your test)
>> FS_DAX
Hi Theodore,
I wonder if you had chance to set the kernel configs from Felix to 
enable DAX in xfstests.

I've been trying to test FS DAX on my side using virtio-fs + QEMU. 
Unfortunately, Im having some problems setting up the environment with 
the guest kernel. Could you share your VM (QEMU or GCE) setup to run it 
with xfstests?

Regards,
Alex S.

>>
>> 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 
> following:
>
> kernel config:
> EFI_FAKE_MEMMAP
> RUNTIME_TESTING_MENU
> TEST_HMM=m
>
> 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.
> efi_fake_mem=1G@...00000000:0x40000,1G@...40000000:0x40000
>
> To run the hmm_test in generic device type pass the SP addresses to 
> the sh script.
> sudo ./test_hmm.sh 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