Re: [PATCH 11/14] arm64: dts: Add initial device tree support for EXYNOS7

[Marc Zyngier <marc.zyngier@arm.com>]

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@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...