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Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework |
Date: |
Wed, 29 Aug 2007 22:18:46 +0100 |
User-agent: |
KMail/1.9.7 |
> If this is the case, it means we don't need anything complicated. Devices
> map themselves straight into the system address space at the appropriate
> slot address (no plug-n-play to worry about), and device "DMA" goes via the
> IOMMU.
Further searching by google suggests I may be wrong.
The alternative is that the controller maps the 32-bit VA onto a device
select+28-bit address, using some as-yet undiscovered mechanism.
There are then a couple of different options for how the CPU/memory bus is
accessed:
a) The IOMMU is one or more slave devices, than feed the 28-bit address
possibly plus a few other bits from the device ID into the translation table.
This effectively allows you to map a proportion of the SBus 32-bit master VA
space onto CPU address space via the IOMMU, and map the remainder onto
devices on the same bus. For a system with <=8 slots per bus a fixed mapping
using the first 2G as 256Mb for each slot and the top 2G for IOMMU is
entirely feasible.
b) The 32-bit SBus VA is looked up directly into the IOMMU. Each IOMMU entry
can refer to either a CPU address, or a device+28-bit address on the local
SBUS.
Paul
- [Qemu-devel] Re: PATCH, RFC: Generic DMA framework, (continued)
- [Qemu-devel] Re: PATCH, RFC: Generic DMA framework, Blue Swirl, 2007/08/24
- Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework, Paul Brook, 2007/08/24
- Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework, Fabrice Bellard, 2007/08/24
- Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework, Paul Brook, 2007/08/24
- Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework, Fabrice Bellard, 2007/08/26
- Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework, Blue Swirl, 2007/08/26
- Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework, Blue Swirl, 2007/08/28
- Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework, Paul Brook, 2007/08/28
- Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework, Blue Swirl, 2007/08/29
- Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework, Paul Brook, 2007/08/29
- Re: [Qemu-devel] Re: PATCH, RFC: Generic DMA framework,
Paul Brook <=