From: Jason Gunthorpe <jgg@ziepe.ca>
To: Will Deacon <will@kernel.org>
Cc: Shyam Saini <shyamsaini@linux.microsoft.com>,
thierry.reding@gmail.com, robin.murphy@arm.com, robh@kernel.org,
joro@8bytes.org, iommu@lists.linux.dev,
linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
virtualization@lists.linux.dev, jacob.pan@linux.microsoft.com,
eric.auger@redhat.com, code@tyhicks.com,
eahariha@linux.microsoft.com, vijayb@linux.microsoft.com,
bboscaccy@linux.microsoft.com, saravanak@google.com,
krzk+dt@kernel.org, conor+dt@kernel.org, lizhi.hou@amd.com,
clement.leger@bootlin.com
Subject: Re: [PATCH v4 3/4] arm-smmu: select suitable MSI IOVA
Date: Fri, 19 Sep 2025 09:08:39 -0300 [thread overview]
Message-ID: <20250919120839.GV1326709@ziepe.ca> (raw)
In-Reply-To: <aM0HQ51DelZW_Rt8@willie-the-truck>
On Fri, Sep 19, 2025 at 08:33:23AM +0100, Will Deacon wrote:
> pieces and will need to work on the userspace side. It's not like
> MSI_IOVA2 is magically going to work (and I bet it won't be tested).
It could, if someone checks the default memory map a second constant
could be selected that works.
> > Nicolin has some patches on the iommufd side to let userspace select
> > the MSI address instead, but they are not done yet.
>
> Maybe we should just wait for that? Carrying a temporary hack with ABI
> implications to support broken hardware isn't particularly compelling
> to me.
This patch would still be needed for kernel users.
Arguably the kernel users should just be using the iova allocator from
dma-iommu.c. This whole hard coded constant/sneaky uapi is just a hack
to make vfio work..
So maybe if the single constant doesn't work we could set some
indication that the caller must allocate the MSI iova, the kernel can
use the dma-iommu allocator and VFIO can just refuse to use the device
for now.
Jason
next prev parent reply other threads:[~2025-09-19 12:08 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-09 15:45 [PATCH v4 0/4] arm-smmu: select suitable MSI IOVA Shyam Saini
2025-09-09 15:45 ` [PATCH v4 1/4] arm-smmu: move MSI_IOVA macro definitions Shyam Saini
2025-09-09 15:45 ` [PATCH v4 2/4] iommu/of: fix device tree configuration for PCI devices Shyam Saini
2025-09-24 17:44 ` Robin Murphy
2025-09-09 15:45 ` [PATCH v4 3/4] arm-smmu: select suitable MSI IOVA Shyam Saini
2025-09-18 16:49 ` Will Deacon
2025-09-18 22:43 ` Jason Gunthorpe
2025-09-19 7:33 ` Will Deacon
2025-09-19 12:08 ` Jason Gunthorpe [this message]
2025-09-23 15:56 ` Shyam Saini
2025-09-23 16:19 ` Jason Gunthorpe
2025-09-24 18:59 ` Robin Murphy
2025-09-09 15:46 ` [PATCH v4 4/4] drivers: iommu: refactor arm_smmu_get_resv_regions Shyam Saini
2025-09-09 15:58 ` Jason Gunthorpe
2025-09-15 16:28 ` Shyam Saini
2025-09-15 22:59 ` Jason Gunthorpe
2025-09-13 0:23 ` kernel test robot
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