From: Ralph Campbell <rcampbell@nvidia.com>
To: Jason Gunthorpe <jgg@mellanox.com>
Cc: Jerome Glisse <jglisse@redhat.com>,
John Hubbard <jhubbard@nvidia.com>,
Christoph Hellwig <hch@lst.de>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 3/3] mm/hmm/test: add self tests for HMM
Date: Thu, 31 Oct 2019 10:28:12 -0700 [thread overview]
Message-ID: <a6b49a4e-a194-ce0b-685f-5e597072aeee@nvidia.com> (raw)
In-Reply-To: <20191031124200.GJ22766@mellanox.com>
On 10/31/19 5:42 AM, Jason Gunthorpe wrote:
> On Wed, Oct 30, 2019 at 05:14:30PM -0700, Ralph Campbell wrote:
>
>>> Well, that is good, is it also under drivers/char? It kind feels like
>>> it should not be there...
>>
>> I think most of the test modules live in lib/ but I wasn't sure that
>> was the right place for the HMM test driver.
>> If you think that is better, I can easily move it.
>
> It would be good to get the various test people involved in this, I
> really don't know.
OK.
>>>>> It seems especially over-complicated to use a full page table layout
>>>>> for this, wouldn't something simple like an xarray be good enough for
>>>>> test purposes?
>>>>
>>>> Possibly. A page table is really just a lookup table from virtual address
>>>> to pfn/page. Part of the rationale was to mimic what a real device
>>>> might do.
>>>
>>> Well, but the details of the page table layout don't see really
>>> important to this testing, IMHO.
>>
>> One problem with XArray is that on 32-bit machines the value would
>> need to be u64 to hold a pfn which won't fit in a ULONG_MAX.
>> I guess we could make the driver 64-bit only.
>
> Why would a 32 bit machine need a 64 bit pfn?
>
> Jason
>
On x86, Physical Address Extension (PAE) uses a 64 bit PTE.
See arch/x86/include/asm/pgtable_32_types.h which includes
arch/x86/include/asm/pgtable-3level_types.h.
next prev parent reply other threads:[~2019-10-31 17:28 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-23 19:55 [PATCH v3 0/3] HMM tests and minor fixes Ralph Campbell
2019-10-23 19:55 ` [PATCH v3 1/3] mm/hmm: make full use of walk_page_range() Ralph Campbell
2019-10-29 17:40 ` Jason Gunthorpe
2019-10-23 19:55 ` [PATCH v3 2/3] mm/hmm: allow snapshot of the special zero page Ralph Campbell
2019-10-23 20:27 ` Jerome Glisse
2019-10-24 9:27 ` David Hildenbrand
2019-10-29 17:27 ` Jason Gunthorpe
2019-10-23 19:55 ` [PATCH v3 3/3] mm/hmm/test: add self tests for HMM Ralph Campbell
2019-10-23 20:28 ` Jerome Glisse
2019-10-23 21:55 ` Ralph Campbell
2019-10-29 17:58 ` Jason Gunthorpe
2019-10-29 21:16 ` Ralph Campbell
2019-10-29 23:12 ` Jason Gunthorpe
2019-10-31 0:14 ` Ralph Campbell
2019-10-31 12:42 ` Jason Gunthorpe
2019-10-31 17:28 ` Ralph Campbell [this message]
2019-10-31 17:34 ` Jason Gunthorpe
2019-10-31 17:48 ` Ralph Campbell
2019-10-30 18:34 ` Qian Cai
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