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

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Message-ID: <577B0B2C.8010300@linux.intel.com>
Date:	Tue, 5 Jul 2016 09:19:40 +0800
From:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:	Neo Jia <cjia@...dia.com>
Cc:	Paolo Bonzini <pbonzini@...hat.com>, 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 07/04/2016 11:33 PM, Neo Jia wrote:

>>>
>>> Sorry, I think I misread the "allocation" as "mapping". We only delay the
>>> cpu mapping, not the allocation.
>>
>> So how to understand your statement:
>> "at that moment nobody has any knowledge about how the physical mmio gets virtualized"
>>
>> The resource, physical MMIO region, has been allocated, why we do not know the physical
>> address mapped to the VM?
>>
>
>>>From a device driver point of view, the physical mmio region never gets allocated until
> the corresponding resource is requested by clients and granted by the mediated device driver.

Hmm... but you told me that you did not delay the allocation. :(

So it returns to my original question: why not allocate the physical mmio region in mmap()?