From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Alex Williamson <alex.williamson@redhat.com>,
Jason Gunthorpe <jgg@nvidia.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Marc Zyngier <maz@kernel.org>,
ankita@nvidia.com, naoya.horiguchi@nec.com,
oliver.upton@linux.dev, aniketa@nvidia.com, cjia@nvidia.com,
kwankhede@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com,
acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com,
danw@nvidia.com, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
Lorenzo Pieralisi <lpieralisi@kernel.org>,
Clint Sbisa <csbisa@amazon.com>,
osamaabb@amazon.com
Subject: Re: [PATCH v3 1/6] kvm: determine memory type from VMA
Date: Tue, 25 Jul 2023 16:18:48 +1000 [thread overview]
Message-ID: <0101c83334721e28b603211c427941e8d31ea9d8.camel@kernel.crashing.org> (raw)
In-Reply-To: <20230717123524.0cefedd0.alex.williamson@redhat.com>
On Mon, 2023-07-17 at 12:35 -0600, Alex Williamson wrote:
> On Sun, 16 Jul 2023 19:30:23 -0300
> Jason Gunthorpe <jgg@nvidia.com> wrote:
>
> > On Sun, Jul 16, 2023 at 08:09:02AM -0700, Catalin Marinas wrote:
> >
> > > In terms of security for arm64 at least, Device vs Normal NC (or nc vs
> > > wc in Linux terminology) doesn't make much difference with the former
> > > occasionally being worse. The kernel would probably trust the DPDK code
> > > if it allows direct device access.
> >
> > RDMA and DRM already allow device drivers to map WC to userspace on
> > demand, we expect the platform to support this.
> >
> > > > So the userspace component needs to be responsible for selecting the
> > > > mapping, the same way using the PCI sysfs resource files today allows
> > > > to do that by selecting the _wc variant.
> > >
> > > I guess the sysfs interface is just trying to work around the VFIO
> > > limitations.
> >
> > I think just nobody has ever asked for VFIO WC support. The main
> > non-VM user is DPDK and none of the NIC drivers have wanted this (DPDK
> > applications areis more of throughput than latency focused typically)
>
> Yes, QEMU can't know whether the device or driver want a WC BAR
> mapping, so we've left it for KVM manipulation relative to VM use
> cases. Nobody has followed through with a complete proposal to enable
> it otherwise for direct userspace driver access, but I don't think
> there's opposition to providing such a thing. Thanks,
Ok, this is really backburner work for me but I'll try to cook up a POC
patch in the near (hopefully) future along the lines of the subregions
I proposed and we can discuss from there.
Cheers,
Ben.
next prev parent reply other threads:[~2023-07-25 6:25 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-05 18:01 [PATCH v3 0/6] Expose GPU memory as coherently CPU accessible ankita
2023-04-05 18:01 ` [PATCH v3 1/6] kvm: determine memory type from VMA ankita
2023-04-12 12:43 ` Marc Zyngier
2023-04-12 13:01 ` Jason Gunthorpe
2023-05-31 11:35 ` Catalin Marinas
2023-06-14 12:44 ` Jason Gunthorpe
2023-07-14 8:10 ` Benjamin Herrenschmidt
2023-07-16 15:09 ` Catalin Marinas
2023-07-16 22:30 ` Jason Gunthorpe
2023-07-17 18:35 ` Alex Williamson
2023-07-25 6:18 ` Benjamin Herrenschmidt [this message]
2023-04-05 18:01 ` [PATCH v3 2/6] vfio/nvgpu: expose GPU device memory as BAR1 ankita
2023-04-05 21:07 ` kernel test robot
2023-04-05 18:01 ` [PATCH v3 3/6] mm: handle poisoning of pfn without struct pages ankita
2023-04-05 21:07 ` kernel test robot
2023-05-09 9:51 ` HORIGUCHI NAOYA(堀口 直也)
2023-05-15 11:18 ` Ankit Agrawal
2023-05-23 5:43 ` HORIGUCHI NAOYA(堀口 直也)
2023-04-05 18:01 ` [PATCH v3 4/6] mm: Add poison error check in fixup_user_fault() for mapped PFN ankita
2023-04-05 18:01 ` [PATCH v3 5/6] mm: Change ghes code to allow poison of non-struct PFN ankita
2023-04-05 18:01 ` [PATCH v3 6/6] vfio/nvgpu: register device memory for poison handling ankita
2023-04-05 20:24 ` Zhi Wang
2023-04-05 21:50 ` kernel test robot
2023-05-24 9:53 ` Dan Carpenter
2023-04-06 12:07 ` [PATCH v3 0/6] Expose GPU memory as coherently CPU accessible David Hildenbrand
2023-04-12 8:43 ` Ankit Agrawal
2023-04-12 9:48 ` Marc Zyngier
2023-04-12 12:28 ` Marc Zyngier
2023-04-12 12:53 ` Jason Gunthorpe
2023-04-13 9:52 ` Marc Zyngier
2023-04-13 13:19 ` Jason Gunthorpe
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=0101c83334721e28b603211c427941e8d31ea9d8.camel@kernel.crashing.org \
--to=benh@kernel.crashing.org \
--cc=acurrid@nvidia.com \
--cc=alex.williamson@redhat.com \
--cc=aniketa@nvidia.com \
--cc=ankita@nvidia.com \
--cc=apopple@nvidia.com \
--cc=catalin.marinas@arm.com \
--cc=cjia@nvidia.com \
--cc=csbisa@amazon.com \
--cc=danw@nvidia.com \
--cc=jgg@nvidia.com \
--cc=jhubbard@nvidia.com \
--cc=kvm@vger.kernel.org \
--cc=kwankhede@nvidia.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lpieralisi@kernel.org \
--cc=maz@kernel.org \
--cc=naoya.horiguchi@nec.com \
--cc=oliver.upton@linux.dev \
--cc=osamaabb@amazon.com \
--cc=targupta@nvidia.com \
--cc=vsethi@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).