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From: Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: [PATCH 0/6] MSI portability cleanups
Date: Tue, 30 Jan 2007 20:32:19 +0100
To: Paul Mackerras <paulus@samba.org>
Cc: tony.luck@intel.com, grundler@parisc-linux.org, jeff@garzik.org,
	mingo@elte.hu, linux-kernel@vger.kernel.org,
	kyle@parisc-linux.org, linuxppc-dev@ozlabs.org,
	"Eric W. Biederman" <ebiederm@xmission.com>, greg@kroah.com,
	shaohua.li@intel.com, linux-pci@atrey.karlin.mff.cuni.cz,
	David Miller <davem@davemloft.net>, brice@myri.com
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> I just got an answer from the hypervisor architects.  It turns out
> that the hardware _does_ prevent the device from sending MSI messages
> to another partition.  The OS _can_ write whatever it likes to the MSI
> address and data registers.  It can potentially lose interrupts (or, I
> expect, get the device isolated by EEH) but it can't disrupt another
> partition.

The OS however has to write the values the HV wants to
the device, or things won't work -- so the HV can just
as well do it itself.  Also, pulling all the work into
the HV makes for a cleaner, more generic design (who
knows what hardware will show up within the next few
years, the HV interface had better be prepared).


Segher