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Re: [Qemu-devel] [PATCH 2/6] PCI DMA API
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH 2/6] PCI DMA API |
Date: |
Sun, 30 Mar 2008 10:18:14 +0000 |
User-agent: |
KMail/1.9.9 |
On Saturday 29 March 2008, Anthony Liguori wrote:
> This patch introduces a PCI DMA API and some generic code to support other
> DMA APIs. Two types are introduced: PhysIOVector and IOVector. A DMA API
> maps a PhysIOVector, which is composed of target_phys_addr_t, into an
> IOVector, which is composed of void *.
Devices should not be using IOVector. They should either use the DMA copy
routines to copy from a PhysIOVector into a local buffer, or they should pass
a PhysIOVector to a block/network read/write routine. The DMA API should
allow devices to be agnostic about how DMA is implemented. They should not be
trying to manually implement zero copy.
> This enables zero-copy IO to be preformed without introducing assumptions
> of phys_ram_base. This API is at the PCI device level to enable support of
> per-device IOMMU remapping.
By my reading it *requires* bridges be zero-copy. For big-endian targets we
need to ability to byteswap accesses.
Some description (in the form of source comments) of how it's meant to be used
would also be helpful.
Paul
- [Qemu-devel] [PATCH 3/6] virtio for QEMU, (continued)
Re: [Qemu-devel] [PATCH 2/6] PCI DMA API,
Paul Brook <=
[Qemu-devel] Re: [kvm-devel] [PATCH 2/6] PCI DMA API, Avi Kivity, 2008/03/30
[Qemu-devel] [PATCH 4/6] virtio network driver, Anthony Liguori, 2008/03/29