From: Jason Gunthorpe <jgg@nvidia.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Manoj Vishwanathan <manojvishy@google.com>,
Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Joerg Roedel <joro@8bytes.org>,
linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
iommu@lists.linux.dev, linux-kernel@vger.kernel.org,
David Dillow <dillow@google.com>
Subject: Re: [PATCH v1 0/4] vfio/iommu: Flag to allow userspace to set DMA buffers system cacheable
Date: Mon, 26 Aug 2024 20:17:49 -0300 [thread overview]
Message-ID: <20240826231749.GM3773488@nvidia.com> (raw)
In-Reply-To: <20240826110447.6522e0a7.alex.williamson@redhat.com>
On Mon, Aug 26, 2024 at 11:04:47AM -0600, Alex Williamson wrote:
> On Mon, 26 Aug 2024 07:16:37 +0000
> Manoj Vishwanathan <manojvishy@google.com> wrote:
>
> > Hi maintainers,
> >
> > This RFC patch introduces the ability for userspace to control whether
> > device (DMA) buffers are marked as cacheable, enabling them to utilize
> > the system-level cache.
> >
> > The specific changes made in this patch are:
> >
> > * Introduce a new flag in `include/linux/iommu.h`:
> > * `IOMMU_SYS_CACHE` - Indicates if the associated page should be cached in the system's cache hierarchy.
> > * Add `VFIO_DMA_MAP_FLAG_SYS_CACHE` to `include/uapi/linux/vfio.h`:
You'll need a much better description of what this is supposed to do
when you resend it.
IOMMU_CACHE already largely means that pages should be cached.
So I don't know what ARM's "INC_OCACHE" actually is doing. Causing
writes to land in a cache somewhere in hierarchy? Something platform
specific? I have no idea. By your description it sounds similar to the
x86 data placement stuff, whatever that was called, and the more
modern TPH approach.
Jason
next prev parent reply other threads:[~2024-08-26 23:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-26 7:16 [PATCH v1 0/4] vfio/iommu: Flag to allow userspace to set DMA buffers system cacheable Manoj Vishwanathan
2024-08-26 7:16 ` [PATCH v1 1/4] iommu: Add IOMMU_SYS_CACHE flag for system cache control Manoj Vishwanathan
2024-08-26 7:16 ` [PATCH v1 2/4] iommu/io-pgtable-arm: Force outer cache for page-level MAIR via user flag Manoj Vishwanathan
2024-08-26 7:16 ` [PATCH v1 3/4] vfio: Add VFIO_DMA_MAP_FLAG_SYS_CACHE to control device access to system cache Manoj Vishwanathan
2024-08-26 7:16 ` [PATCH v1 4/4] vfio/type1: Add support for VFIO_DMA_MAP_FLAG_SYS_CACHE Manoj Vishwanathan
2024-08-26 17:04 ` [PATCH v1 0/4] vfio/iommu: Flag to allow userspace to set DMA buffers system cacheable Alex Williamson
2024-08-26 17:36 ` Manoj Vishwanathan
2024-08-26 23:17 ` Jason Gunthorpe [this message]
2024-08-27 17:31 ` Robin Murphy
2024-08-28 2:55 ` Manoj Vishwanathan
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