From: Jason Gunthorpe <jgg@ziepe.ca>
To: Xu Yilun <yilun.xu@linux.intel.com>
Cc: Sean Christopherson <seanjc@google.com>,
Ackerley Tng <ackerleytng@google.com>,
Alexey Kardashevskiy <aik@amd.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Kevin Tian <kevin.tian@intel.com>, Joerg Roedel <joro@8bytes.org>,
Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Steve Sistare <steven.sistare@oracle.com>,
Nicolin Chen <nicolinc@nvidia.com>,
iommu@lists.linux.dev, linux-coco@lists.linux.dev,
Dan Williams <dan.j.williams@intel.com>,
Santosh Shukla <santosh.shukla@amd.com>,
"Pratik R . Sampat" <prsampat@amd.com>,
Fuad Tabba <tabba@google.com>,
"Aneesh Kumar K . V" <aneesh.kumar@kernel.org>,
michael.roth@amd.com, vannapurve@google.com
Subject: Re: [RFC PATCH kernel] iommufd: Allow mapping from KVM's guest_memfd
Date: Fri, 27 Feb 2026 09:18:15 -0400 [thread overview]
Message-ID: <20260227131815.GG44359@ziepe.ca> (raw)
In-Reply-To: <aaFzgGTpZI0eZWdD@yilunxu-OptiPlex-7050>
On Fri, Feb 27, 2026 at 06:35:44PM +0800, Xu Yilun wrote:
> Will cause host machine check and host restart, same as host CPU
> accessing encrypted memory. Intel TDX has no lower level privilege
> protection table so the wrong accessing will actually impact the
> memory encryption engine.
Blah, of course it does.
So Intel needs a two step synchronization to wipe the IOPTEs before
any shared private conversions and restore the right ones after.
AMD needs a nasty HW synchronization with RMP changes, but otherwise
wants to map the entire physical space.
ARM doesn't care much, I think it could safely do either approach?
These are very different behaviors so I would expect that userspace
needs to signal which of the two it wants.
It feels like we need a fairly complex dedicated synchronization logic
in iommufd coupled to the shared/private machinery in guestmemfd
Not really sure how to implement the Intel version right now, it is
sort of like a nasty version of SVA..
Jason
next prev parent reply other threads:[~2026-02-27 13:18 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-25 7:52 [RFC PATCH kernel] iommufd: Allow mapping from KVM's guest_memfd Alexey Kardashevskiy
2026-02-25 13:55 ` Sean Christopherson
2026-02-26 6:47 ` Alexey Kardashevskiy
2026-02-26 19:27 ` Jason Gunthorpe
2026-02-27 11:03 ` Xu Yilun
2026-02-26 8:19 ` Ackerley Tng
2026-02-26 19:07 ` Jason Gunthorpe
2026-02-26 22:40 ` Sean Christopherson
2026-02-27 0:21 ` Jason Gunthorpe
2026-02-27 0:28 ` Sean Christopherson
2026-02-27 1:09 ` Jason Gunthorpe
2026-02-27 10:35 ` Xu Yilun
2026-02-27 13:18 ` Jason Gunthorpe [this message]
2026-02-28 4:14 ` Xu Yilun
2026-02-28 18:29 ` 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=20260227131815.GG44359@ziepe.ca \
--to=jgg@ziepe.ca \
--cc=ackerleytng@google.com \
--cc=aik@amd.com \
--cc=aneesh.kumar@kernel.org \
--cc=dan.j.williams@intel.com \
--cc=iommu@lists.linux.dev \
--cc=joro@8bytes.org \
--cc=kevin.tian@intel.com \
--cc=kvm@vger.kernel.org \
--cc=linux-coco@lists.linux.dev \
--cc=linux-kernel@vger.kernel.org \
--cc=michael.roth@amd.com \
--cc=nicolinc@nvidia.com \
--cc=pbonzini@redhat.com \
--cc=prsampat@amd.com \
--cc=robin.murphy@arm.com \
--cc=santosh.shukla@amd.com \
--cc=seanjc@google.com \
--cc=steven.sistare@oracle.com \
--cc=tabba@google.com \
--cc=vannapurve@google.com \
--cc=will@kernel.org \
--cc=yilun.xu@linux.intel.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