Re: [Xen-devel] [PATCH 1/9] Xen Share: Simplified I/O Mechanism

[Harry Butterworth <harry@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>]

On Wed, 2006-06-07 at 12:35 +1000, Rusty Russell wrote:
> On Tue, 2006-06-06 at 15:47 +0100, Harry Butterworth wrote:
> > On Tue, 2006-06-06 at 15:35 +1000, Rusty Russell wrote:
> > > This introduces a page "share" mechanism to xen: an alternative to
> > > both cross-domain binding of event channels, and grant tables.
> > 
> > Why do you think an alternative to event channels and grant tables is
> > needed?

<big snip>

> If the
> frontend or backend dies, there is no restriction on cleaning up its
> memory.

This is a good answer.  In my use of grant-tables for the USB driver, I
ended up with the possibility of one side having to poll indefinitely
for the other side to free up its memory with no guarantee of this ever
happening.  The memory couldn't be reused until it was freed because the
other side had a writeable mapping (reusing even just a readable mapping
would have been a security hole).

I think a fix for this problem is a significant win for your approach
over grant-tables.

> Hope that clarifies!

Yes thanks.

Harry.


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