From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yang Zhang <yang.zhang.wz@gmail.com>
Subject: Re: VFIO based vGPU(was Re: [Announcement] 2015-Q3 release of XenGT -
 a Mediated ...)
Date: Wed, 27 Jan 2016 09:34:46 +0800
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Cc: Alex Williamson <alex.williamson@redhat.com>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"Lv, Zhiyuan" <zhiyuan.lv@intel.com>,
	"Ruan, Shuai" <shuai.ruan@intel.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	qemu-devel <qemu-devel@nongnu.org>,
	"igvt-g@lists.01.org" <igvt-g@ml01.01.org>,
	Neo Jia <cjia@nvidia.com>
To: Jike Song <jike.song@intel.com>
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On 2016/1/27 8:06, Jike Song wrote:
> On 01/26/2016 10:05 PM, Yang Zhang wrote:
>> On 2016/1/26 15:41, Jike Song wrote:
>>
>>> We will need to extend:
>>>
>>> 	- VFIO_DEVICE_GET_REGION_INFO
>>>
>>>
>>> a) adding a flag: DONT_MAP. For example, the MMIO of vgpu
>>> should be trapped instead of being mmap-ed.
>>
>> I may not in the context, but i am curious how to handle the DONT_MAP in
>> vfio driver? Since there are no real MMIO maps into the region and i
>> suppose the access to the region should be handled by vgpu in i915
>> driver, but currently most of the mmio accesses are handled by Qemu.
>>
>
> Hi Yang,
>
> MMIO accesses are supposed to be handled in kernel, without vm-exiting
> to QEMU, similar to in-kernel irqchip :)

The question is current vfio doesn't support it. The long discussion 
between Alex and Kevin is what i am to understand how KVMGT works under 
vfio framework.


-- 
best regards
yang