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Re: [PATCH 10/18] KVM/MIPS32-VZ: Add API for VZ-ASE Capability

To: David Daney <ddaney.cavm@gmail.com>
Subject: Re: [PATCH 10/18] KVM/MIPS32-VZ: Add API for VZ-ASE Capability
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu, 30 May 2013 19:51:15 +0200
Cc: Sanjay Lal <sanjayl@kymasys.com>, kvm@vger.kernel.org, linux-mips@linux-mips.org, Ralf Baechle <ralf@linux-mips.org>, Gleb Natapov <gleb@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>
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Il 30/05/2013 19:07, David Daney ha scritto:
> On 05/28/2013 09:34 AM, Paolo Bonzini wrote:
>> Il 19/05/2013 07:47, Sanjay Lal ha scritto:
>>> - Add API to allow clients (QEMU etc.) to check whether the H/W
>>>    supports the MIPS VZ-ASE.
>>
>> Why does this matter to userspace?  Do the userspace have some way to
>> detect if the kernel is unmodified or minimally-modified?
>>
> 
> There are (will be) two types of VM presented by MIPS KVM:
> 
> 1) That provided by the initial patch where a faux-MIPS is emulated and
> all kernel code must be in the USEG address space.
> 
> 2) Real MIPS, addressing works as per the architecture specification.
> 
> Presumably the user-space client would like to know which of these are
> supported, as well as be able to select the desired model.

Understood.  It's really two different machine types.

> I don't know the best way to do this, but I agree that
> KVM_CAP_MIPS_VZ_ASE is probably not the best name for it.
> 
> My idea was to have the arg of the KVM_CREATE_VM ioctl specify the
> desired style

Ok.  How complex is it?  Do you plan to do this when the patches are
"really ready" for Linus' tree?

Paolo

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