On Thu, Aug 28, 2014 at 06:37:19PM +0100, Marc Zyngier wrote: > On 28/08/14 18:30, Mark Rutland wrote: > > On Thu, Aug 28, 2014 at 06:27:04PM +0100, Marc Zyngier wrote: > >> On 28/08/14 18:03, Mark Rutland wrote: > >> > >>> From 67104ad5a56e4c18f9c41f06af028b7561740afd Mon Sep 17 00:00:00 2001 > >>> From: Mark Rutland <mark.rutland@xxxxxxx> > >>> Date: Thu, 28 Aug 2014 17:41:03 +0100 > >>> Subject: [PATCH] Doc: dt: arch_timer: discourage clock-frequency use > >>> > >>> The ARM Generic Timer (AKA the architected timer, arm_arch_timer) > >>> features a CPU register (CNTFRQ) which firmware is intended to > >>> initialize, and non-secure software can read to determine the frequency > >>> of the timer. On CPUs with secure state, this register cannot be written > >>> from non-secure states. > >>> > >>> The firmware of early SoCs featuring the timer did not correctly > >>> initialize CNTFRQ correctly on all CPUs, requiring the frequency to be > >>> described in DT as a workaround. This workaround is not complete however > >>> as CNTFRQ is exposed to all software in a privileged non-secure mode, > >>> including KVM guests. The firmware and DTs for recent SoCs have followed > >> > >> I believe Xen is also affected by this. > > > > True. > > > > s/KVM/KVM\/Xen/, then? > > Yup. Or "including guests running under a hypervisor" Ah, that sounds better. I'll use that for the next posting. > I expect this to be such a fundamental problem that all hypervisors > will trip over on that one (Jailhouse definitely does). Yeah, this is a generic problem. Mark. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
