From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 00/16] arm/arm64: Workaround misprogrammed CNTFRQ
Date: Mon, 24 Jul 2017 13:19:59 +0100 [thread overview]
Message-ID: <20170724121958.GC29919@arm.com> (raw)
In-Reply-To: <20170721171542.27639-1-marc.zyngier@arm.com>
On Fri, Jul 21, 2017 at 06:15:26PM +0100, Marc Zyngier wrote:
> It is an unfortunate situation that CNTFRQ{,_EL0} is often
> misprogrammed from the firmware side, leaving it up to the kernel to
> work around it. This is usually done by providing an alternative
> frequency in the Device Tree.
>
> Unfortunately, CNTFRQ is accessible from EL0, giving userspace the
> wrong frequency, and potentially a different frequency per CPU, which
> is definitely not what you want. A possible workaround is to trap this
> into the kernel and to emulate it (together with the VDSO being
> disabled), and this is what this series is achieving.
Which userspace is actually affected by a broken CNTFRQ register? I suspect
most users will be more upset at losing their (perfectly functional) vDSO
acceleration than they are about having a broken CNTFRQ value that is hardly
ever used, especially since this affects quite a few systems.
Will
next prev parent reply other threads:[~2017-07-24 12:19 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-21 17:15 [PATCH 00/16] arm/arm64: Workaround misprogrammed CNTFRQ Marc Zyngier
2017-07-21 17:15 ` [PATCH 01/16] arm64: Use arch_timer_get_rate when trapping CNTFRQ_EL0 Marc Zyngier
2017-07-21 17:15 ` [PATCH 02/16] arm64: Add decoding macros for CP15_32 and CP15_64 traps Marc Zyngier
2017-07-21 17:15 ` [PATCH 03/16] arm64: compat: Add separate CP15 trapping hook Marc Zyngier
2017-07-21 17:15 ` [PATCH 04/16] arm64: compat: Add condition code checks and IT advance Marc Zyngier
2017-07-21 17:15 ` [PATCH 05/16] arm64: compat: Add cp15_32 and cp15_64 handler arrays Marc Zyngier
2017-07-21 17:15 ` [PATCH 06/16] arm64: compat: Add CNTVCT trap handler Marc Zyngier
2017-07-21 17:15 ` [PATCH 07/16] arm64: compat: Add CNTFRQ " Marc Zyngier
2017-07-21 17:15 ` [PATCH 08/16] ARM: Let arm_check_condition work with Thumb Marc Zyngier
2017-07-21 17:15 ` [PATCH 09/16] ARM: Check condition code before trying to handle an UNDEF Marc Zyngier
2017-07-21 17:15 ` [PATCH 10/16] ARM: Add arm_advance_itstate helper Marc Zyngier
2017-07-21 17:15 ` [PATCH 11/16] ARM: Advance the IT state on successful emulation of an UNDEF Marc Zyngier
2017-07-21 17:15 ` [PATCH 12/16] ARM: Simplify condition checks in swp_handler Marc Zyngier
2017-07-21 17:15 ` [PATCH 13/16] ARM: Handle trapping of CNTVCT from userspace Marc Zyngier
2017-07-21 17:15 ` [PATCH 14/16] ARM: Handle trapping of CNTFRQ " Marc Zyngier
2017-07-21 17:15 ` [PATCH 15/16] clocksource/arm_arch_timer: Add helper to disable VDSO fastpath Marc Zyngier
2017-07-21 17:15 ` [PATCH 16/16] clocksource/arm_arch_timer: Trap user access to CNT{VCT, FRQ} if CNTFRQ is invalid Marc Zyngier
2017-07-24 12:19 ` Will Deacon [this message]
2017-07-24 12:48 ` [PATCH 00/16] arm/arm64: Workaround misprogrammed CNTFRQ Marc Zyngier
2017-07-24 13:12 ` Will Deacon
2017-07-24 13:35 ` Marc Zyngier
2017-07-25 11:46 ` Will Deacon
-- strict thread matches above, loose matches on Subject: below --
2017-07-21 17:14 Marc Zyngier
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