Message-ID: <4C062928.8040003@redhat.com>
Date: Wed, 02 Jun 2010 12:49:28 +0300
From: Avi Kivity <avi@redhat.com>
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To: Joerg Roedel <joro@8bytes.org>
CC: "Michael S. Tsirkin" <mst@redhat.com>, Tom Lyon <pugs@cisco.com>,
       linux-kernel@vger.kernel.org, kvm@vger.kernel.org, chrisw@sous-sol.org,
       hjk@linutronix.de, gregkh@suse.de, aafabbri@cisco.com,
       scofeldm@cisco.com
Subject: Re: [PATCH] VFIO driver: Non-privileged user level PCI drivers
References: <20100530130332.GM27611@redhat.com> <4C026497.8070901@redhat.com> <20100530145309.GO27611@redhat.com> <4C03A285.7060902@redhat.com> <20100531171007.GA6516@redhat.com> <4C04C085.1030107@redhat.com> <20100601095532.GA9178@redhat.com> <4C04E0E0.3070006@redhat.com> <20100601104651.GA9415@redhat.com> <4C050013.2020701@redhat.com> <20100602094527.GD964@8bytes.org>
In-Reply-To: <20100602094527.GD964@8bytes.org>
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On 06/02/2010 12:45 PM, Joerg Roedel wrote:
> On Tue, Jun 01, 2010 at 03:41:55PM +0300, Avi Kivity wrote:
>    
>> On 06/01/2010 01:46 PM, Michael S. Tsirkin wrote:
>>      
>    
>>> Main difference is that vhost works fine with unlocked
>>> memory, paging it in on demand. iommu needs to unmap
>>> memory when it is swapped out or relocated.
>>>
>>>        
>> So you'd just take the memory map and not pin anything.  This way you
>> can reuse the memory map.
>>
>> But no, it doesn't handle the dirty bitmap, so no go.
>>      
> IOMMU mapped memory can not be swapped out because we can't do demand
> paging on io-page-faults with current devices. We have to pin _all_
> userspace memory that is mapped into an IOMMU domain.
>    

vhost doesn't pin memory.

What I proposed is to describe the memory map using an object (fd), and 
pass it around to clients that use it: kvm, vhost, vfio.  That way you 
maintain the memory map in a central location and broadcast changes to 
clients.  Only a vfio client would result in memory being pinned.

It can still work, but the interface needs to be extended to include 
dirty bitmap logging.

-- 
error compiling committee.c: too many arguments to function

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