Re: [virtio-dev] Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver

[Paolo Bonzini]

On 18/11/2016 05:07, Michael S. Tsirkin wrote:
> On Fri, Nov 18, 2016 at 12:32:06PM +0900, Namhyung Kim wrote:
>> Btw I prefer using the kvmtool for my kernel work since it's much more
>> simpler..
> 
> Up to you but then you should extend that to support 1.0 spec.
> I strongly object to adding to the list of legacy interfaces
> we need to maintain.

I object to adding paravirtualization unless there is a good reason why
the usual mechanisms for physical machines cannot be used.  The cost of
maintaining a spec, two device implementations (kvmtool+qemu) and a
driver is not small, plus it will not work on older kernels.

Paolo
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Re: [PATCH 1/3] virtio: Basic implementation of virtio pstore driver

[Paolo Bonzini]

On 18/11/2016 04:32, Namhyung Kim wrote:
>> In addition, the firmware will need to reserve a few KB of RAM for the error 
>> log
>> address range (I checked a real system and it reserves 8KB).  The first eight
>> bytes are needed for the record identifier interface, because there's no such
>> thing as 64-bit I/O ports, and the rest can be used for the actual buffer.
> 
> Is there a limit on the size?  It'd be great if it can use a few MB..

Yes, you can make it customizable.

>>> Also I need to control pstore driver like using bigger buffer,
>>> enabling specific message types and so on if ERST supports.  Is it
>>> possible for ERST to provide such information?
>>
>> It's the normal pstore driver, same as on a real server.  What exactly do you
>> need?
> 
> Well, I don't want to send additional pstore messages to the device if
> it cannot handle them properly - for example, ftrace message should not
> overwrite kmsg dump.  It'd be great if device somehow could expose
> acceptable message types to the driver IMHO.

This is something that you have to do in the usual kernel pstore
infrastructure.  It should not be specific to virtualization.

Paolo

> Btw I prefer using the kvmtool for my kernel work since it's much more
> simpler..

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