Re: [Qemu-devel] [big lock] Discussion about the convention of device's DMA each other after breaking down biglock

[Avi Kivity]

On 09/30/2012 10:48 AM, liu ping fan wrote:
> On Sun, Sep 30, 2012 at 4:13 PM, Avi Kivity <address@hidden> wrote:
>> On 09/29/2012 11:20 AM, liu ping fan wrote:
>>>
>>> Do we have iommus in qemu now,
>>
>> We do, but they're hacked into the scsi layer, see hw/sun4m_iommu.c.  I
>> don't know if it's a standalone iommu on real hardware or whether it is
>> part of the HBA.
>>
>>> since there are no separate phys_maps
>>> for real address and dev's virt address, and I think the iommu is only
>>> needed by host, not guest, so need not emulated by qemu.
>>
>> Eventually we will emulate iommus for x86 too, so we need to consider them.
>>
> For nested guest?  The address translation is like nested mmu?

Yes.


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