[PATCH 11/14] arm64: dts: Add initial device tree support for EXYNOS7
mark.rutland at arm.com
Thu Aug 28 10:45:03 PDT 2014
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 at arm.com>
> >>> 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.
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