linux-kernel - Re: [PATCH 0/2] KVM: MMU: support VMAs that got remap_pfn

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Date:	Wed, 6 Jul 2016 10:00:46 +0800
From:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:	Paolo Bonzini <pbonzini@...hat.com>, Neo Jia <cjia@...dia.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Kirti Wankhede <kwankhede@...dia.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH 0/2] KVM: MMU: support VMAs that got remap_pfn_range-ed



On 07/05/2016 08:18 PM, Paolo Bonzini wrote:
>
>
> On 05/07/2016 07:41, Neo Jia wrote:
>> On Thu, Jun 30, 2016 at 03:01:49PM +0200, Paolo Bonzini wrote:
>>> The vGPU folks would like to trap the first access to a BAR by setting
>>> vm_ops on the VMAs produced by mmap-ing a VFIO device.  The fault handler
>>> then can use remap_pfn_range to place some non-reserved pages in the VMA.
>>>
>>> KVM lacks support for this kind of non-linear VM_PFNMAP mapping, and these
>>> patches should fix this.
>>
>> Hi Paolo,
>>
>> I have tested your patches with the mediated passthru patchset that is being
>> reviewed in KVM and QEMU mailing list.
>>
>> The fault handler gets called successfully and the previously mapped memory gets
>> unmmaped correctly via unmap_mapping_range.
>
> Great, then I'll include them in 4.8.

Code is okay, but i still suspect if this implementation, fetch mmio pages in fault
handler, is needed. We'd better include these patches after the design of vfio
framework is decided.