Re: the P2M/VP patch merge plan (was Re: [Xen-ia64-devel] [PATCH][RFC][TAKE5] the P2M/VP patches)

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Mon, Apr 24, 2006 at 04:21:27PM +0200, Tristan Gingold wrote:

> just a question: is P2M/VP SMP-h/g safe ?
> Please do the merge even if not yet SMP ready.  I will work to re-enable SMP.

Unfortunately no for both SMP-h/g.
It doesn't boot without nosmp xen boot option because the P2M table
is not protected at least.
A lock sould be introduced to protect it.
Please define a wrapper function, something like p2m_lock()/p2m_unlock().
Prehaps read/write spin lock might be better for performance,
but it can be tuned later. We should use simple spin lock as a first step.

I'm guessing that there may be a race between TLB/vhpt fulsh and
p2m conversion, but I'm not sure.
Carefull code analysis is required.

-- 
yamahata

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