Re: [Qemu-devel] [PATCH V3 WIP 3/3] disable vhost_verify_ring_mappings check

[Paolo Bonzini]

Il 29/03/2013 03:53, Nicholas A. Bellinger ha scritto:
> On Thu, 2013-03-28 at 06:13 -0400, Paolo Bonzini wrote:
>>> I think it's the right thing to do, but maybe not the right place
>>> to do this, need to reset after all IO is done, before
>>> ring memory is write protected.
>>
>> Our emails are crossing each other unfortunately, but I want to
>> reinforce this: ring memory is not write protected.
> 
> Understood.  However, AFAICT the act of write protecting these ranges
> for ROM generates the offending callbacks to vhost_set_memory().
> 
> The part that I'm missing is if ring memory is not being write protected
> by make_bios_readonly_intel(), why are the vhost_set_memory() calls
> being invoked..?

Because mappings change for the region that contains the ring.  vhost
doesn't know yet that the changes do not affect ring memory,
vhost_set_memory() is called exactly to ascertain that.

Paolo

> 
>> Remember that
>> SeaBIOS can even provide virtio-scsi access to DOS, so you must
>> not reset the device.  It must remain functional all the time,
>> and the OS's own driver will reset it when it's started.
>>
> 
> Mmmm, so a vp_reset() is out of the question then..
> 
> --nab
> 
> 
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