From: Logan Gunthorpe <logang@deltatee.com>
To: Jerome Glisse <jglisse@redhat.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J . Wysocki" <rafael@kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
Christian Koenig <christian.koenig@amd.com>,
Felix Kuehling <Felix.Kuehling@amd.com>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>, Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Joerg Roedel <jroedel@suse.de>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>
Subject: Re: [RFC PATCH 3/5] mm/vma: add support for peer to peer to device vma
Date: Tue, 29 Jan 2019 18:17:43 -0700 [thread overview]
Message-ID: <655a335c-ab91-d1fc-1ed3-b5f0d37c6226@deltatee.com> (raw)
In-Reply-To: <20190129234752.GR3176@redhat.com>
On 2019-01-29 4:47 p.m., Jerome Glisse wrote:
> The whole point is to allow to use device memory for range of virtual
> address of a process when it does make sense to use device memory for
> that range. So they are multiple cases where it does make sense:
> [1] - Only the device is accessing the range and they are no CPU access
> For instance the program is executing/running a big function on
> the GPU and they are not concurrent CPU access, this is very
> common in all the existing GPGPU code. In fact AFAICT It is the
> most common pattern. So here you can use HMM private or public
> memory.
> [2] - Both device and CPU access a common range of virtul address
> concurrently. In that case if you are on a platform with cache
> coherent inter-connect like OpenCAPI or CCIX then you can use
> HMM public device memory and have both access the same memory.
> You can not use HMM private memory.
>
> So far on x86 we only have PCIE and thus so far on x86 we only have
> private HMM device memory that is not accessible by the CPU in any
> way.
I feel like you're just moving the rug out from under us... Before you
said ignore HMM and I was asking about the use case that wasn't using
HMM and how it works without HMM. In response, you just give me *way*
too much information describing HMM. And still, as best as I can see,
managing DMA mappings (which is different from the userspace mappings)
for GPU P2P should be handled by HMM and the userspace mappings should
*just* link VMAs to HMM pages using the standard infrastructure we
already have.
>> And what struct pages are actually going to be backing these VMAs if
>> it's not using HMM?
>
> When you have some range of virtual address migrated to HMM private
> memory then the CPU pte are special swap entry and they behave just
> as if the memory was swapped to disk. So CPU access to those will
> fault and trigger a migration back to main memory.
This isn't answering my question at all... I specifically asked what is
backing the VMA when we are *not* using HMM.
Logan
next prev parent reply other threads:[~2019-01-30 1:18 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-29 17:47 [RFC PATCH 0/5] Device peer to peer (p2p) through vma jglisse
2019-01-29 17:47 ` [RFC PATCH 1/5] pci/p2p: add a function to test peer to peer capability jglisse
2019-01-29 18:24 ` Logan Gunthorpe
2019-01-29 19:44 ` Greg Kroah-Hartman
2019-01-29 19:53 ` Jerome Glisse
2019-01-29 20:44 ` Logan Gunthorpe
2019-01-29 21:00 ` Jerome Glisse
2019-01-29 19:56 ` Alex Deucher
2019-01-29 20:00 ` Jerome Glisse
2019-01-29 20:24 ` Logan Gunthorpe
2019-01-29 21:28 ` Alex Deucher
2019-01-30 10:25 ` Christian König
2019-01-29 17:47 ` [RFC PATCH 2/5] drivers/base: " jglisse
2019-01-29 18:26 ` Logan Gunthorpe
2019-01-29 19:54 ` Jerome Glisse
2019-01-29 19:46 ` Greg Kroah-Hartman
2019-01-29 19:56 ` Jerome Glisse
2019-01-29 17:47 ` [RFC PATCH 3/5] mm/vma: add support for peer to peer to device vma jglisse
2019-01-29 18:36 ` Logan Gunthorpe
2019-01-29 19:11 ` Jerome Glisse
2019-01-29 19:24 ` Logan Gunthorpe
2019-01-29 19:44 ` Jerome Glisse
2019-01-29 20:43 ` Logan Gunthorpe
2019-01-30 7:52 ` Christoph Hellwig
2019-01-29 19:32 ` Jason Gunthorpe
2019-01-29 19:50 ` Jerome Glisse
2019-01-29 20:24 ` Jason Gunthorpe
2019-01-29 20:44 ` Jerome Glisse
2019-01-29 23:02 ` Jason Gunthorpe
2019-01-30 0:08 ` Jerome Glisse
2019-01-30 4:30 ` Jason Gunthorpe
2019-01-30 15:43 ` Jerome Glisse
2019-01-29 20:39 ` Logan Gunthorpe
2019-01-29 20:57 ` Jerome Glisse
2019-01-29 21:30 ` Logan Gunthorpe
2019-01-29 21:50 ` Jerome Glisse
2019-01-29 22:58 ` Logan Gunthorpe
2019-01-29 23:47 ` Jerome Glisse
2019-01-30 1:17 ` Logan Gunthorpe [this message]
2019-01-30 2:48 ` Jerome Glisse
2019-01-30 4:18 ` Jason Gunthorpe
2019-01-30 8:00 ` Christoph Hellwig
2019-01-30 15:49 ` Jerome Glisse
2019-01-30 19:06 ` Jason Gunthorpe
2019-01-30 19:45 ` Logan Gunthorpe
2019-01-30 19:59 ` Jason Gunthorpe
2019-01-30 21:01 ` Logan Gunthorpe
2019-01-30 21:50 ` Jason Gunthorpe
2019-01-30 22:52 ` Logan Gunthorpe
2019-01-30 23:30 ` Jason Gunthorpe
2019-01-31 8:13 ` Christoph Hellwig
2019-01-31 15:37 ` Jerome Glisse
2019-01-31 19:02 ` Jason Gunthorpe
2019-01-31 19:19 ` Logan Gunthorpe
2019-01-31 19:54 ` Jason Gunthorpe
2019-01-31 19:35 ` Jerome Glisse
2019-01-31 19:44 ` Logan Gunthorpe
2019-01-31 19:58 ` Jason Gunthorpe
2019-01-30 17:17 ` Logan Gunthorpe
2019-01-30 18:56 ` Jason Gunthorpe
2019-01-30 19:22 ` Jerome Glisse
2019-01-30 19:38 ` Jason Gunthorpe
2019-01-30 20:00 ` Logan Gunthorpe
2019-01-30 20:11 ` Jason Gunthorpe
2019-01-30 20:43 ` Jerome Glisse
2019-01-30 20:50 ` Jason Gunthorpe
2019-01-30 21:45 ` Jerome Glisse
2019-01-30 21:56 ` Jason Gunthorpe
2019-01-30 22:30 ` Jerome Glisse
2019-01-30 22:33 ` Jason Gunthorpe
2019-01-30 22:47 ` Jerome Glisse
2019-01-30 22:51 ` Jason Gunthorpe
2019-01-30 22:58 ` Jerome Glisse
2019-01-30 19:52 ` Logan Gunthorpe
2019-01-30 20:35 ` Jerome Glisse
2019-01-29 20:58 ` Jason Gunthorpe
2019-01-30 8:02 ` Christoph Hellwig
2019-01-30 10:33 ` Koenig, Christian
2019-01-30 15:55 ` Jerome Glisse
2019-01-30 17:26 ` Christoph Hellwig
2019-01-30 17:32 ` Logan Gunthorpe
2019-01-30 17:39 ` Jason Gunthorpe
2019-01-30 18:05 ` Jerome Glisse
2019-01-30 17:44 ` Jason Gunthorpe
2019-01-30 18:13 ` Logan Gunthorpe
2019-01-30 18:50 ` Jerome Glisse
2019-01-31 8:02 ` Christoph Hellwig
2019-01-31 15:03 ` Jerome Glisse
2019-01-30 19:19 ` Jason Gunthorpe
2019-01-30 19:48 ` Logan Gunthorpe
2019-01-30 20:44 ` Jason Gunthorpe
2019-01-31 8:05 ` Christoph Hellwig
2019-01-31 15:11 ` Jerome Glisse
2019-01-29 17:47 ` [RFC PATCH 4/5] mm/hmm: add support for peer to peer to HMM device memory jglisse
2019-01-29 17:47 ` [RFC PATCH 5/5] mm/hmm: add support for peer to peer to special device vma jglisse
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