From: Fred Griffoul <griffoul@gmail.com>
To: "Jason Gunthorpe" <jgg@ziepe.ca>,
"Christian König" <christian.koenig@amd.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Marc Zyngier <maz@kernel.org>, Oliver Upton <oupton@kernel.org>,
Sumit Semwal <sumit.semwal@linaro.org>,
Kevin Tian <kevin.tian@intel.com>,
David Woodhouse <dwmw2@infradead.org>,
Ackerley Tng <ackerleytng@google.com>,
Joey Gouly <joey.gouly@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>,
Steffen Eiden <seiden@linux.ibm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Thomas Gleixner <tglx@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H . Peter Anvin" <hpa@zytor.com>, Joerg Roedel <joro@8bytes.org>,
Robin Murphy <robin.murphy@arm.com>,
Alex Williamson <alex@shazbot.org>, Shuah Khan <shuah@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
iommu@lists.linux.dev, linux-media@vger.kernel.org,
dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org,
linux-kselftest@vger.kernel.org,
linux-trace-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [RFC PATCH 2/6] dma-buf: Add get_phys() to describe a physical run
Date: Mon, 12 Oct 2026 15:29:46 +0000 [thread overview]
Message-ID: <20261012152946.63489-1-griffoul@gmail.com> (raw)
In-Reply-To: <20261012144616.GF14213@ziepe.ca>
On Mon, Oct 12, 2026 at 11:46:16AM -0300, Jason Gunthorpe wrote:
> I don't want to keep expanding this hack in iommufd. If dmabuf is to
> be used then dmabuf needs to provide a pluggable way to fill the
> iommu_domain that many exporters can plug into. I don't want to
> hardwire every exporter into iommufd, that makes no sense.
>
> The existing arrangement is to motivate solving this problem
> generically, not something to be expanded on.
Agreed. The iommufd registry I mentioned above was never posted, and I
have dropped it.
The series I posted since takes another route, without dma-buf:
https://lore.kernel.org/all/20261006183235.16576-1-griffoul@gmail.com/
It adds a small interface in mm for drivers that own memory. Such a
driver hands out files, and for each page of a file it tells the caller
which frame backs it. iommufd maps the file with IOMMU_IOAS_MAP_FILE and
builds the iommu_domain itself, and the driver revokes a range when it
changes. So iommufd never knows which driver it is talking to, and there
is no symbol_get(). guest_memfd uses the same files for the guest. The
iommufd part is patch 5:
https://lore.kernel.org/all/20261006183235.16576-6-griffoul@gmail.com/
The iommufd part is mainly there to show the interface, and it needs
more work. Its revoke unmaps and then remaps, so a device can hit a
hole. I would rebuild it on the REPLACE operation David discussed with
you at LPC, with the scratch page as a quirk on the IOAS.
Is this the kind of generic interface you had in mind, or would you
rather have it hang off dma-buf?
Thanks,
Fred
next prev parent reply other threads:[~2026-10-12 15:29 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-20 11:03 [RFC PATCH v2 00/11] KVM: Allow alternative providers of guest_memfd backed by PFNMAP memory David Woodhouse
2026-07-20 11:03 ` [RFC PATCH v2 01/11] KVM: selftests: sev_smoke_test: Only run VM types the host offers David Woodhouse
2026-07-20 11:03 ` [RFC PATCH v2 02/11] KVM: selftests: sev_init2_tests: Derive SEV availability from KVM David Woodhouse
2026-07-20 11:03 ` [RFC PATCH v2 03/11] KVM: SEV: Remove struct page dependency from SNP gmem paths David Woodhouse
2026-07-20 11:03 ` [RFC PATCH v2 04/11] KVM: guest_memfd: Introduce guest memory ops and route native gmem through them David Woodhouse
2026-07-20 11:03 ` [RFC PATCH v2 05/11] iommufd: Look up private-interconnect phys via exporter symbols David Woodhouse
2026-07-20 11:03 ` [RFC PATCH v2 06/11] iommufd: Plumb dma-buf memory-type (RAM vs MMIO) through the phys map David Woodhouse
2026-07-20 11:03 ` [RFC PATCH v2 07/11] KVM: guest_memfd: Add ops-driven page revocation David Woodhouse
2026-07-20 11:03 ` [RFC PATCH v2 08/11] samples/kvm: Add guest_memfd backing sample David Woodhouse
2026-07-20 11:03 ` [RFC PATCH v2 09/11] selftests/kvm: gmem_provider KVM-only tests David Woodhouse
2026-07-20 11:03 ` [RFC PATCH v2 10/11] selftests/kvm: gmem_provider iommufd tests David Woodhouse
2026-07-20 11:03 ` [RFC PATCH v2 11/11] samples/kvm, selftests/kvm: Allow the gmem_provider NVMe DMA test on arm64 David Woodhouse
2026-07-20 15:11 ` [RFC PATCH v2 00/11] KVM: Allow alternative providers of guest_memfd backed by PFNMAP memory Paolo Bonzini
2026-07-20 16:39 ` David Woodhouse
2026-07-23 0:24 ` Ackerley Tng
2026-07-23 9:40 ` David Woodhouse
2026-07-23 16:01 ` Ackerley Tng
2026-10-05 9:55 ` [RFC PATCH 0/6] KVM: guest_memfd: back guest_memfd with an imported dma-buf Fred Griffoul
2026-10-05 9:55 ` [RFC PATCH 1/6] KVM: guest_memfd: Add a writable result to get_pfn() Fred Griffoul
2026-10-05 9:55 ` [RFC PATCH 2/6] dma-buf: Add get_phys() to describe a physical run Fred Griffoul
2026-10-05 10:07 ` Christian König
2026-10-05 13:20 ` Fred Griffoul
2026-10-05 14:53 ` Christian König
2026-10-12 14:46 ` Jason Gunthorpe
2026-10-12 15:29 ` Fred Griffoul [this message]
2026-10-05 9:55 ` [RFC PATCH 3/6] dma-buf: Add ranged mapping invalidation Fred Griffoul
2026-10-05 10:08 ` Christian König
2026-10-05 9:55 ` [RFC PATCH 4/6] dma-buf: Allow dynamic attach without a device Fred Griffoul
2026-10-05 9:55 ` [RFC PATCH 5/6] KVM: guest_memfd: Add dma-buf backing Fred Griffoul
2026-10-05 9:55 ` [RFC PATCH 6/6] samples/kvm, selftests/kvm: Exercise " Fred Griffoul
2026-10-06 18:32 ` [RFC PATCH 0/9] mm: Memory providers for guest_memfd and iommufd Fred Griffoul
2026-10-06 18:32 ` [PATCH 1/9] KVM: guest_memfd: Add a writable result to get_pfn() Fred Griffoul
2026-10-06 18:32 ` [PATCH 2/9] mm: Add memory providers Fred Griffoul
2026-10-06 18:32 ` [PATCH 3/9] KVM: guest_memfd: Add a memory provider backing Fred Griffoul
2026-10-06 18:32 ` [PATCH 4/9] iommufd: Track the domains of pages that are not pinned Fred Griffoul
2026-10-06 18:32 ` [PATCH 5/9] iommufd: Map memory provider files Fred Griffoul
2026-10-06 18:32 ` [PATCH 6/9] iommufd/selftest: Add mock-domain IOVA queries Fred Griffoul
2026-10-06 18:32 ` [PATCH 7/9] iommufd/selftest: Add a mock memory provider Fred Griffoul
2026-10-06 18:32 ` [PATCH 8/9] samples/kvm: Add a memory provider sample Fred Griffoul
2026-10-06 18:32 ` [PATCH 9/9] KVM: selftests: Test a memory provider shared by KVM and iommufd Fred Griffoul
2026-10-10 7:36 ` [RFC PATCH 0/9] mm: Memory providers for guest_memfd " Aneesh Kumar K.V
2026-10-12 9:58 ` Fred Griffoul
2026-10-12 10:07 ` David Woodhouse
2026-10-12 14:41 ` Ackerley Tng
2026-10-12 15:07 ` Fred Griffoul
2026-10-12 15:13 ` David Woodhouse
2026-10-12 15:48 ` Fred Griffoul
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