From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sasha Levin <levinsasha928@gmail.com>
Subject: Re: [PATCH] MMIO: Make coalesced mmio use a device per zone
Date: Tue, 19 Jul 2011 12:53:02 +0300
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Cc: kvm@vger.kernel.org, Marcelo Tosatti <mtosatti@redhat.com>
To: Avi Kivity <avi@redhat.com>
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On Tue, 2011-07-19 at 11:48 +0300, Avi Kivity wrote:
> On 07/19/2011 11:10 AM, Sasha Levin wrote:
> > This patch changes coalesced mmio to create one mmio device per
> > zone instead of handling all zones in one device.
> >
> > Doing so enables us to take advantage of existing locking and prevents
> > a race condition between coalesced mmio registration/unregistration
> > and lookups.
> >
> >
> >
> >   #include "coalesced_mmio.h"
> >
> > +static spinlock_t lock;
> > +static LIST_HEAD(head);
> 
> Make these per-guest instead of global.  The lock may be contended, and 
> the list shouldn't hold items from different guests (why is it needed, 
> anyway?)
> 

We only need the list for removal, since we only have the range we want
to remove, and we want to find all devices which contain this range.

> The coalesced mmio devices will now contend with other io devices for 
> NR_IOBUS_DEVS, so need to increase that (by KVM_COALESCED_MMIO_ZONE_MAX).
> 

-- 

Sasha.