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Re: [Qemu-devel] Re: [PATCH 1/5] Add target memory mapping API
From: |
Ian Jackson |
Subject: |
Re: [Qemu-devel] Re: [PATCH 1/5] Add target memory mapping API |
Date: |
Mon, 26 Jan 2009 12:23:57 +0000 |
Anthony Liguori writes ("Re: [Qemu-devel] Re: [PATCH 1/5] Add target memory
mapping API"):
> Ian Jackson wrote:
> > I think my most recently sketched-out proposal (where the caller
> > passes a DMA sg list to the mapping request function) doesn't have
> > these deadlocks ?
>
> But what do you do with a DMA request that cannot possibly be bounced
> but that can be split? In other words, a DMA request to 1G of MMIO
> memory that is disk access. We can absolutely split that into multiple
> requests.
You impose a maximum size for any DMA request; that is, a maximum size
that callers of the DMA API are allowed to request. Any larger
request is a bug. Callers who might want to try to map bigger blocks
need to be able to split.
Alternatively you can have the API return an `amount mapped' on the
callback, but state that this number will always be at least
DMA_MAP_SG_GUARANTEE_MIN if at least that amount was requested.
Ian.
- [Qemu-devel] Re: [PATCH 1/5] Add target memory mapping API, (continued)
[Qemu-devel] Re: [PATCH 1/5] Add target memory mapping API, Anthony Liguori, 2009/01/20
Re: [Qemu-devel] Re: [PATCH 1/5] Add target memory mapping API, Anthony Liguori, 2009/01/21
Re: [Qemu-devel] Re: [PATCH 1/5] Add target memory mapping API, Ian Jackson, 2009/01/22
Re: [Qemu-devel] Re: [PATCH 1/5] Add target memory mapping API, Anthony Liguori, 2009/01/22
Re: [Qemu-devel] Re: [PATCH 1/5] Add target memory mapping API,
Ian Jackson <=
Re: [Qemu-devel] Re: [PATCH 1/5] Add target memory mapping API, Anthony Liguori, 2009/01/26
[Qemu-devel] Re: Add target memory mapping API, Mike Day, 2009/01/21
[Qemu-devel] [PATCH 2/5] Add map client retry notification, Avi Kivity, 2009/01/18
Re: [Qemu-devel] [PATCH 0/5] Direct memory access for devices, Blue Swirl, 2009/01/19