From: Peter Xu <peterx@redhat.com>
To: Mattias Nissler <mnissler@rivosinc.com>,
Peter Maydell <peter.maydell@linaro.org>
Cc: stefanha@redhat.com, jag.raman@oracle.com, qemu-devel@nongnu.org,
"Philippe Mathieu-Daudé" <philmd@linaro.org>,
john.levon@nutanix.com, "David Hildenbrand" <david@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Marcel Apfelbaum" <marcel.apfelbaum@gmail.com>,
"Elena Ufimtseva" <elena.ufimtseva@oracle.com>
Subject: Re: [PATCH v8 0/5] Support message-based DMA in vfio-user server
Date: Mon, 4 Mar 2024 18:25:39 +0800 [thread overview]
Message-ID: <ZeWho6ZW41tg0rob@x1n> (raw)
In-Reply-To: <20240304100554.1143763-1-mnissler@rivosinc.com>
On Mon, Mar 04, 2024 at 02:05:49AM -0800, Mattias Nissler wrote:
> This series adds basic support for message-based DMA in qemu's vfio-user
> server. This is useful for cases where the client does not provide file
> descriptors for accessing system memory via memory mappings. My motivating use
> case is to hook up device models as PCIe endpoints to a hardware design. This
> works by bridging the PCIe transaction layer to vfio-user, and the endpoint
> does not access memory directly, but sends memory requests TLPs to the hardware
> design in order to perform DMA.
>
> Note that more work is needed to make message-based DMA work well: qemu
> currently breaks down DMA accesses into chunks of size 8 bytes at maximum, each
> of which will be handled in a separate vfio-user DMA request message. This is
> quite terrible for large DMA accesses, such as when nvme reads and writes
> page-sized blocks for example. Thus, I would like to improve qemu to be able to
> perform larger accesses, at least for indirect memory regions. I have something
> working locally, but since this will likely result in more involved surgery and
> discussion, I am leaving this to be addressed in a separate patch.
No objection from my side memory-wise. It'll be good to get some words
from Paolo if possible.
Copy Peter Maydell due to the other relevant discussion.
https://lore.kernel.org/qemu-devel/20240228125939.56925-1-heinrich.schuchardt@canonical.com/
--
Peter Xu
next prev parent reply other threads:[~2024-03-04 10:26 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-04 10:05 [PATCH v8 0/5] Support message-based DMA in vfio-user server Mattias Nissler
2024-03-04 10:05 ` [PATCH v8 1/5] softmmu: Per-AddressSpace bounce buffering Mattias Nissler
2024-03-04 10:05 ` [PATCH v8 2/5] softmmu: Support concurrent bounce buffers Mattias Nissler
2024-03-04 10:05 ` [PATCH v8 3/5] Update subprojects/libvfio-user Mattias Nissler
2024-03-04 10:05 ` [PATCH v8 4/5] vfio-user: Message-based DMA support Mattias Nissler
2024-03-04 10:05 ` [PATCH v8 5/5] vfio-user: Fix config space access byte order Mattias Nissler
2024-03-04 10:25 ` Peter Xu [this message]
2024-03-28 7:53 ` [PATCH v8 0/5] Support message-based DMA in vfio-user server Mattias Nissler
2024-05-06 14:44 ` Peter Xu
2024-05-06 21:07 ` Mattias Nissler
2024-05-07 9:43 ` Mattias Nissler
2024-05-07 12:52 ` Philippe Mathieu-Daudé
2024-05-07 12:59 ` Mattias Nissler
2024-05-06 15:01 ` Stefan Hajnoczi
2024-05-06 21:05 ` Mattias Nissler
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