On 28/08/14 18:30, Mark Rutland wrote:

On Thu, Aug 28, 2014 at 06:27:04PM +0100, Marc Zyngier wrote:

quoted

On 28/08/14 18:03, Mark Rutland wrote:

quoted

From 67104ad5a56e4c18f9c41f06af028b7561740afd Mon Sep 17 00:00:00 2001
From: Mark Rutland <mark.rutland@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", I expect this to
be such a fundamental problem that all hypervisors will trip over on
that one (Jailhouse definitely does).

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...