From: Jason Gunthorpe <jgg@nvidia.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Nicolin Chen <nicolinc@nvidia.com>,
Alex Williamson <alex.williamson@redhat.com>,
"Tian, Kevin" <kevin.tian@intel.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>
Subject: Re: RMRR device on non-Intel platform
Date: Wed, 26 Apr 2023 11:17:45 -0300 [thread overview]
Message-ID: <ZEkyicpaAJJ+pIXg@nvidia.com> (raw)
In-Reply-To: <5ff0d72b-a7b8-c8a9-60e5-396e7a1ef363@arm.com>
On Wed, Apr 26, 2023 at 02:53:53PM +0100, Robin Murphy wrote:
> Give QEMU a way to tell IOMMUFD to associate that 0x08080000 address with a
> given device as an MSI target. IOMMUFD then ensures that the S2 mapping
> exists from that IPA to the device's real ITS (I vaguely remember Eric had a
> patch to pre-populate an MSI cookie with specific pages, which may have been
> heading along those lines).
This isn't the main problem - already for most cases iommufd makes it
so the ITS page is at 0x8000000. We can fix qemu to also use
0x8000000 in the ACPI - it already hardwires this for the RMRR part.
We can even make the kernel return the value so it isn't hardwired,
easy stuff..
> QEMU will presumably also need a way to pass the VA down to IOMMUFD when it
> sees the guest programming the MSI (possibly it could pass the IPA at the
> same time so we don't need a distinct step to set up S2 beforehand?) - once
> the underlying physical MSI configuration comes back from the PCI layer,
> that VA just needs to be dropped in to replace the original msi_msg address.
This is the main problem. What ioctl passes the VA, and how does it plumb
down into the irq_chip..
This is where everyone gets scared, I think. There is a thick mass of
IRQ plumbing and locking between those two points
And then it only solves MSI, not the bigger picture..
> TBH at that point it may be easier to just not have a cookie in the S2
> domain at all when nesting is enabled, and just let IOMMUFD make the ITS
> mappings directly for itself.
Yes, I'd like to get there so replace can work.
Jason
next prev parent reply other threads:[~2023-04-26 14:17 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-20 6:52 RMRR device on non-Intel platform Tian, Kevin
2023-04-20 14:15 ` Alex Williamson
2023-04-20 14:19 ` Robin Murphy
2023-04-20 14:49 ` Alex Williamson
2023-04-20 16:55 ` Robin Murphy
2023-04-20 21:49 ` Alex Williamson
2023-04-21 4:10 ` Tian, Kevin
2023-04-21 11:33 ` Jason Gunthorpe
2023-04-21 11:34 ` Robin Murphy
2023-04-23 8:23 ` Tian, Kevin
2023-04-21 12:04 ` Jason Gunthorpe
2023-04-21 12:29 ` Robin Murphy
2023-04-21 12:45 ` Jason Gunthorpe
2023-04-21 17:22 ` Robin Murphy
2023-04-21 17:58 ` Jason Gunthorpe
2023-04-25 14:48 ` Robin Murphy
2023-04-25 15:58 ` Jason Gunthorpe
2023-04-26 8:39 ` Tian, Kevin
2023-04-26 12:24 ` Robin Murphy
2023-04-26 12:58 ` Jason Gunthorpe
2023-04-25 16:37 ` Nicolin Chen
2023-04-26 11:57 ` Jason Gunthorpe
2023-04-26 13:53 ` Robin Murphy
2023-04-26 14:17 ` Jason Gunthorpe [this message]
2023-04-21 13:21 ` Baolu Lu
2023-04-21 13:33 ` Jason Gunthorpe
2023-04-23 8:24 ` Tian, Kevin
2023-04-24 2:50 ` Baolu Lu
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=ZEkyicpaAJJ+pIXg@nvidia.com \
--to=jgg@nvidia.com \
--cc=alex.williamson@redhat.com \
--cc=iommu@lists.linux.dev \
--cc=kevin.tian@intel.com \
--cc=kvm@vger.kernel.org \
--cc=nicolinc@nvidia.com \
--cc=robin.murphy@arm.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).