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Date: Tue, 26 Mar 2013 15:46:49 +0000 From: Arnd Bergmann <arnd@...db.de> To: Will Deacon <will.deacon@....com> Cc: Stefano Stabellini <stefano.stabellini@...citrix.com>, "xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "konrad.wilk@...cle.com" <konrad.wilk@...cle.com>, Ian Campbell <Ian.Campbell@...rix.com>, Marc Zyngier <Marc.Zyngier@....com>, "linux@....linux.org.uk" <linux@....linux.org.uk>, "nico@...aro.org" <nico@...aro.org> Subject: Re: [PATCH v2 6/6] [RFC] arm: use PSCI if available On Tuesday 26 March 2013, Will Deacon wrote: > > They can even base the implementation of their smp_ops on the current > > psci code, in order to facilitate that I could get rid of psci_ops > > (which initialization is based on device tree) and export the psci_cpu_* > > functions instead, so that they can be called directly by other smp_ops. > > Again, I think this destroys the layering. The whole point is that the PSCI > functions are called from within something that understands precisely how to > talk to the firmware and what it is capable of. Right, we probably the psci smp ops to be separate from the rest of the psci code, but I also think that Stefano is right that we should let any platform use the psci smp ops if possible, rather than having to implement their own. > > > If this can indeed work for the virtual platforms (Xen and KVM), then I > > > think it would be better expressed using `virt' smp_ops, which map directly > > > to PSCI, rather than putting them here. Even then, it's tying KVM and Xen > > > together on the firmware side of things... > > > > Keep in mind that dom0 on Xen boots as a native machine (versatile > > express or exynos5 for example) with a Xen hypervisor node on it. We > > would need to find a way to override the default machine smp_ops with > > a set of xen_smp_ops early at boot. > > I don't like this option very much, I think is fragile. > > Why can't dom0 use whatever smp ops the native machine would use? The part that I'm most interested in is making it possible for a platform to kill off its native smp ops in the kernel by implementing the psci ops. I think it's a good strategy to use psci by default if both platform and psci implementations are available. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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