From: Paolo Bonzini <pbonzini@redhat.com>
To: "Philippe Mathieu-Daudé" <philmd@redhat.com>,
"Peter Maydell" <peter.maydell@linaro.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>,
QEMU Developers <qemu-devel@nongnu.org>,
Bug 1880355 <1880355@bugs.launchpad.net>,
Gerd Hoffmann <kraxel@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Laszlo Ersek <lersek@redhat.com>
Subject: Re: [Bug 1880355] [NEW] Length restrictions for fw_cfg_dma_transfer?
Date: Mon, 25 May 2020 15:59:00 +0200 [thread overview]
Message-ID: <36adab2a-bfb4-c60b-9a5b-5fe741d01325@redhat.com> (raw)
In-Reply-To: <c8326e26-c529-18c1-4bd2-63a5aec071fb@redhat.com>
On 24/05/20 16:27, Philippe Mathieu-Daudé wrote:
>> In an ideal world all our DMA devices would use some kind of common
>> framework or design pattern so they didn't hog all the CPU
>> and/or spend minutes with the BQL held if the guest requests
>> an enormous-sized DMA. In practice many of them just have
>> a simple "loop until the DMA transfer is complete" implementation...
> Is this framework already implemented in the hidden dma-helpers.c?
>
> Apparently this file was written for BlockBackend, but the code seems
> rather generic.
The code is generic, see dma_buf_rw, but the asynchronous code is
currently used only for block devices. Above a certain limit it would
make sense to reuse them to perform dma_buf_rw in the thread pool.
Paolo
next prev parent reply other threads:[~2020-05-25 14:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-24 4:12 [Bug 1880355] [NEW] Length restrictions for fw_cfg_dma_transfer? Alexander Bulekov
2020-05-24 10:30 ` Philippe Mathieu-Daudé
2020-05-24 10:30 ` Philippe Mathieu-Daudé
2020-05-24 13:40 ` Peter Maydell
2020-05-24 13:40 ` Peter Maydell
2020-05-24 14:27 ` Philippe Mathieu-Daudé
2020-05-24 14:27 ` Philippe Mathieu-Daudé
2020-05-25 13:59 ` Paolo Bonzini [this message]
2020-05-25 9:14 ` Mark Cave-Ayland
2020-05-25 9:14 ` Mark Cave-Ayland
2021-06-10 15:50 ` [Bug 1880355] " Thomas Huth
2021-06-14 23:35 ` Alexander Bulekov
2021-06-15 18:17 ` Thomas Huth
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