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Re: [Qemu-devel] [PATCH 2/6] s390: sclp base support
From: |
Christian Borntraeger |
Subject: |
Re: [Qemu-devel] [PATCH 2/6] s390: sclp base support |
Date: |
Mon, 16 Jul 2012 09:04:52 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux i686; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 |
On 14/07/12 10:48, Blue Swirl wrote:
>>>> + cpu_physical_memory_write(sccb, &work_sccb,
>>>> + be16_to_cpu(work_sccb.h.length));
>>>
>>> Perhaps the DMA helpers should be used instead.
>>>
>>
>> Is there any rule what to use under which circumstances.
>
> No, it's a recent addition. Devices (at least those which may be used
> in IOMMU environment) should use DMA helpers for their memory accesses
> in general but virtio may be an exception. I'm not sure which category
> this falls in.
Ok, I read this as, if we need to handle DMA into virtual addresses at some
point in time dma helpers are the way to go.
With SCLP we access real storage (no translation) so I think
cpu_physical_memory_write is fine here.
Christian
- [Qemu-devel] [PATCH 1/6] s390: Fix error handling and condition code of service call, (continued)
- [Qemu-devel] [PATCH 1/6] s390: Fix error handling and condition code of service call, Christian Borntraeger, 2012/07/13
- [Qemu-devel] [PATCH 6/6] s390: make sclp ascii console the default, Christian Borntraeger, 2012/07/13
- [Qemu-devel] [PATCH 5/6] s390: sclp ascii console support, Christian Borntraeger, 2012/07/13
- [Qemu-devel] [PATCH 3/6] s390: sclp event support, Christian Borntraeger, 2012/07/13
- [Qemu-devel] [PATCH 4/6] s390: sclp signal quiesce support, Christian Borntraeger, 2012/07/13
- [Qemu-devel] [PATCH 2/6] s390: sclp base support, Christian Borntraeger, 2012/07/13
- Re: [Qemu-devel] [PATCH 2/6] s390: sclp base support, Andreas Färber, 2012/07/20