linux-kernel - Re: [Alacrityvm-devel] [PATCH v2 2/4] KVM: introduce "xinterface" API for external interaction with guests

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Message-ID: <20091007051047.GA24176@amit-x200.redhat.com>
Date:	Wed, 7 Oct 2009 10:40:47 +0530
From:	Amit Shah <amit.shah@...hat.com>
To:	"Ira W. Snyder" <iws@...o.caltech.edu>
Cc:	Gregory Haskins <gregory.haskins@...il.com>,
	Avi Kivity <avi@...hat.com>,
	David Howells <dhowells@...hat.com>,
	Gregory Haskins <ghaskins@...ell.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	"alacrityvm-devel@...ts.sourceforge.net" 
	<alacrityvm-devel@...ts.sourceforge.net>
Subject: Re: [Alacrityvm-devel] [PATCH v2 2/4] KVM: introduce "xinterface"
	API for external interaction with guests

On (Tue) Oct 06 2009 [11:18:59], Ira W. Snyder wrote:
> 
> The limitation I have is that memory made available from the host system
> (PCI card) as PCI BAR1 must not be migrated around in memory. I can only
> change the address decoding to hit a specific physical address. AFAIK,
> this means it cannot be userspace memory (since the underlying physical
> page could change, or it could be in swap), and must be allocated with
> something like __get_free_pages() or dma_alloc_coherent().

If the dma area is just one page in size, that page can be pinned by the
host (via a hypercall by the guest). If it's more, there is a
reserve-ram patch by Andrea. That'll reserve some RAM area for the guest
that's 1-1 mapped in the host address space. There was a patch posted on
the list sometime back.

		Amit
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