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Date:   Thu, 22 Jul 2021 14:26:48 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     "Sierra Guiza, Alejandro (Alex)" <alex.sierra@amd.com>
Cc:     akpm@linux-foundation.org, Felix.Kuehling@amd.com,
        linux-mm@kvack.org, rcampbell@nvidia.com,
        linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
        amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        hch@lst.de, jglisse@redhat.com
Subject: Re: [PATCH v4 10/13] lib: test_hmm add module param for zone device
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On Thu, Jul 22, 2021 at 11:59:17AM -0500, Sierra Guiza, Alejandro (Alex) wrote:
> 
> On 7/22/2021 7:23 AM, Jason Gunthorpe wrote:
> > On Sat, Jul 17, 2021 at 02:21:32PM -0500, Alex Sierra wrote:
> > > In order to configure device generic in test_hmm, two
> > > module parameters should be passed, which correspon to the
> > > SP start address of each device (2) spm_addr_dev0 &
> > > spm_addr_dev1. If no parameters are passed, private device
> > > type is configured.
> > I don't think tests should need configuration like this, is it really
> > necessary? How can people with normal HW run this test?
> Hi Jason,
> The idea was to add an easy way to validate the codepaths touched by this
> patch series, which make modifications to the migration helpers for device
> generic type pages. We're using CONFIG_EFI_FAKE_MEMMAP to create fake SPM
> devices inside system memory. No special HW needed. And passing the kernel
> parameter efi_fake_mem. Ex. efi_fake_mem=1G@0x100000000:0x40000. I should
> probably need to include a small example of how to set this in the
> test_hmm.sh
> usage().

I don't think anything about hmm is sensitive to how the pages are
acquired - you can't create device generic pages without relying on
FAKE_MEMMAP?

Jason