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From: ebiederm@xmission.com (Eric W. Biederman)
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [RFC/PATCH 4/7] Powerpc MSI implementation
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Date: Tue, 07 Nov 2006 19:43:15 -0700
In-Reply-To: <1162951680.28571.627.camel@localhost.localdomain> (Benjamin
	Herrenschmidt's message of "Wed, 08 Nov 2006 13:08:00 +1100")
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Cc: Matthew Wilcox <matthew@wil.cx>, Greg Kroah-Hartman <greg@kroah.com>,
	Ingo Molnar <mingo@elte.hu>,
	Russell King <rmk-pci@arm.linux.org.uk>, linuxppc-dev@ozlabs.org,
	Thomas Gleixner <tglx@linutronix.de>, linux-pci@atrey.karlin.mff.cuni.cz,
	"David S.Miller" <davem@davemloft.net>
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Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:

> My initial idea was that the msi_info structure would have a variable
> lenght, that is, would end with msi_desc[0] and would be allocated to
> the the right size, but it might suck a bit :-)

That could work.  The whole array of interrupts thing allocated on
device probe, I question a little bit.  I can just about see allocating
another interrupt if you can when a network device start getting another
flow through it.  But it is working well enough at the moment it doesn't
appear time to run out and change the drivers.

>> Hopefully I can look at this a little more this evening and see what we
>> need to do to harmonize the two msi implementations.
>
> Thanks !

I'm still having a hard time wrapping my head around the sanity of not letting
the kernel touch the hardware in the presence of a hypervisor.  How do you cope
with hardware that follows a specification the hypervisor is not aware of?

This seems to be a violation of the principle that the driver knows the hardware
better than some generic layer.

Eric