From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: PCI MSI questions Date: Thu, 24 Jul 2008 08:20:48 +0100 Message-ID: References: <4888452A.76E4.0078.0@novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4888452A.76E4.0078.0@novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jan Beulich , xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On 24/7/08 08:02, "Jan Beulich" wrote: > 1) There currently seems to be a hidden requirement of NR_PIRQS in the > kernel needing to be no smaller than NR_IRQS in the hypervisor. > Otherwise, the pirq returned from PHYSDEVOP_map_pirq may collide > with the dynamic IRQs in the kernel or even be out of range altogether. > Therefore I think that NR_PIRQS has to become a variable defaulting > to 256 but getting initialized from a hypervisor reported value (perhaps > in start_info, or else from a new (sub-)hypercall). Or have the kernel remap the return value of map_pirq into its own PIRQ namespace, and maintain appropriate translation info? Although, it'd be nice to have dynamic NR_IRQS sizing anyway -- people who want to run lots of domUs currently may have to recompile dom0 with more DYNIRQS. > 4) The hypervisor option "msi_irq_enable" seems to be named pretty > oddly - both the "irq" and the "enable" in the name are more or less > redundant. So unless there's a reason for this long a name for an > option that generally I would expect most people want to set (at > least on bigger systems), I'd like to change it into "msi" or, if that's > considered prone for ambiguity, "pci-msi". Also, are there any plans > when to make have default be on rather than off? Renaming sounds sensible. I admit I forgot it was turned off by default. I guess at this point we should turn it on by default immediately after 3.3 has branched. -- Keir