[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20190130173859.GA17915@mellanox.com>
Date: Wed, 30 Jan 2019 17:39:07 +0000
From: Jason Gunthorpe <jgg@...lanox.com>
To: Christoph Hellwig <hch@....de>
CC: Jerome Glisse <jglisse@...hat.com>,
"Koenig, Christian" <Christian.Koenig@....com>,
Logan Gunthorpe <logang@...tatee.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J . Wysocki" <rafael@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
"Kuehling, Felix" <Felix.Kuehling@....com>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Robin Murphy <robin.murphy@....com>,
Joerg Roedel <jroedel@...e.de>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Subject: Re: [RFC PATCH 3/5] mm/vma: add support for peer to peer to device
vma
On Wed, Jan 30, 2019 at 06:26:53PM +0100, Christoph Hellwig wrote:
> On Wed, Jan 30, 2019 at 10:55:43AM -0500, Jerome Glisse wrote:
> > Even outside GPU driver, device driver like RDMA just want to share their
> > doorbell to other device and they do not want to see those doorbell page
> > use in direct I/O or anything similar AFAICT.
>
> At least Mellanox HCA support and inline data feature where you
> can copy data directly into the BAR. For something like a usrspace
> NVMe target it might be very useful to do direct I/O straight into
> the BAR for that.
It doesn't really work like that.
The PCI-E TLP sequence to trigger this feature is very precise, and
the data requires the right headers/etc. Mixing that with O_DIRECT
seems very unlikely.
Jason
Powered by blists - more mailing lists