From mboxrd@z Thu Jan  1 00:00:00 1970
From: Anthony Liguori <anthony@codemonkey.ws>
Subject: Re: [PATCH] Handle vma regions with no backing page	(v2)
Date: Wed, 30 Apr 2008 10:37:24 -0500
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Cc: Carsten Otte <cotte@de.ibm.com>,
	Hollis Blanchard <hollisb@us.ibm.com>,
	kvm-devel@lists.sourceforge.net, Avi Kivity <avi@qumranet.com>,
	Ben-Ami Yassour <benami@il.ibm.com>,
	"Zhang,  Xiantao" <xiantao.zhang@intel.com>
To: Andrea Arcangeli <andrea@qumranet.com>
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Andrea Arcangeli wrote:
> On Tue, Apr 29, 2008 at 06:12:51PM -0500, Anthony Liguori wrote:
>   
>> IIUC PPC correctly, all IO pages have corresponding struct pages.  This 
>> means that get_user_pages() would succeed and you can reference count them? 
>>  In this case, we would never take the VM_PFNMAP path.
>>     
>
> get_user_pages only works on vmas where only pfn with struct page can
> be mapped, but if a struct page exists it doesn't mean get_user_pages
> will succeed. All mmio regions should be marked VM_IO as reading on
> them affects hardware somehow and that prevents get_user_pages to work
> on them regardless if a struct page exists.
>   

Ah, thanks for the clarification.

Regards,

Anthony Liguori

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