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[Qemu-devel] [PATCH 0/2 version 2] fw_cfg: Implement fast "DMA"-type ope
From: |
Richard W.M. Jones |
Subject: |
[Qemu-devel] [PATCH 0/2 version 2] fw_cfg: Implement fast "DMA"-type operation for rapidly copying in kernel, initrd [etc] into the guest |
Date: |
Mon, 19 Jul 2010 11:15:04 +0100 |
User-agent: |
Mutt/1.5.18 (2008-05-17) |
This is the second version of the patch.
We don't use the word "blit" any more, instead this is replaced with
"DMA", even though it's not quite like a DMA operation on physical
hardware.
The guest writes the physical address and size to two 32 bit fw_cfg
variables. Then when the guest issues an ordinary read operation with
the extra FW_CFG_DMA flag set, instead of returning a single byte,
qemu "DMA"s the requested data into the guest memory.
The guest shouldn't be able to request a dma_size larger than the
amount of data in the entry. The patch checks this and adjusts
dma_size.
The guest might select a dma_addr which does not correspond to
physical memory (or dma_addr + dma_size). Reading the code it seems
to be that cpu_physical_memory_write catches this case and will
abort() (so the guest is only harming itself). However I'd quite like
an expert opinion on this ...
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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- [Qemu-devel] [PATCH 0/2] fw_cfg: Implement fast "blit" operation for rapidly copying in kernel, initrd [etc] into the guest, Richard W.M. Jones, 2010/07/17
- [Qemu-devel] [PATCH 1/2] Don't call fw_cfg e->callback if e->callback is NULL., Richard W.M. Jones, 2010/07/17
- [Qemu-devel] [PATCH 2/2] fw_cfg: Add blit operation for copying kernel, initrd, .., Richard W.M. Jones, 2010/07/17
- Re: [Qemu-devel] [PATCH 2/2] fw_cfg: Add blit operation for copying kernel, initrd, .., Aurelien Jarno, 2010/07/18
[Qemu-devel] [PATCH 0/2 version 2] fw_cfg: Implement fast "DMA"-type operation for rapidly copying in kernel, initrd [etc] into the guest,
Richard W.M. Jones <=
[Qemu-devel] [PATCH 2/2 version 3] fw_cfg: Implement fast "DMA"-type operation for rapidly copying in kernel, initrd [etc] into the guest, Richard W.M. Jones, 2010/07/19