linux-kernel - Re: [PATCH v3 15/18] arm64: arch_timer: Enable CNTVCT

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Date:   Mon, 24 Apr 2017 12:26:38 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Hanjun Guo <guohanjun@...wei.com>,
        "Lixiaoping (Timmy)" <lixiaoping3@...wei.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        dann frazier <dann.frazier@...onical.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Scott Wood <oss@...error.net>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        Dingtianhong <dingtianhong@...wei.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v3 15/18] arm64: arch_timer: Enable CNTVCT_EL0 trap if
 workaround is enabled

On Mon, Apr 24, 2017 at 10:33:29AM +0100, Marc Zyngier wrote:
> On 24/04/17 10:14, Hanjun Guo wrote:
> > On 2017/4/24 16:40, Marc Zyngier wrote:
> >> On 24/04/17 09:25, Lixiaoping (Timmy) wrote:
> >>> Sorry about previous email's confidential info. Please forget it.
> >>>
> >>> +#define ESR_ELx_SYS64_ISS_SYS_CNTFRQ	(ESR_ELx_SYS64_ISS_SYS_VAL(3, 3, 14, 0, 0) | \
> >>> +					 ESR_ELx_SYS64_ISS_DIR_READ)
> >>>
> >>> I think (3, 3, 14, 0, 0) should be (3, 3, 0, 14, 0)?
> >> Thanks for spotting this. I assumed that the sys_reg() and
> >> SR_ELx_SYS64_ISS_SYS_VAL() macros took their arguments in the same 
> >> order. That would have been too easy... ;-)
> >>
> >> Amended patch below, please let me know if it works for you.
> >>
> >> Thanks,
> >>
> >> 	M.
> >>
> >> >From 4444c86a97c1a487e12c319fdc197c88631d72b5 Mon Sep 17 00:00:00 2001
> >> From: Marc Zyngier <marc.zyngier@....com>
> >> Date: Mon, 24 Apr 2017 09:04:03 +0100
> >> Subject: [PATCH] arm64: Add CNTFRQ_EL0 trap handler
> >>
> >> We now trap accesses to CNTVCT_EL0 when the counter is broken
> >> enough to require the kernel to mediate the access. But it
> >> turns out that some existing userspace (such as OpenMPI) do
> >> probe for the counter frequency, leading to an UNDEF exception
> >> as CNTVCT_EL0 and CNTFRQ_EL0 share the same control bit.
> >>
> >> The fix is to handle the exception the same way we do for CNTVCT_EL0.
> >>
> >> Fixes: a86bd139f2ae ("arm64: arch_timer: Enable CNTVCT_EL0 trap if workaround is enabled")
> >> Reported-by: Hanjun Guo <guohanjun@...wei.com>
> >> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> >> ---
> > 
> > I tested this patch and the undefined instruction error is gone, I can
> > get the FREQ in the user space now, thank you very much for the quick
> > response.
> > 
> > Tested-by: Hanjun Guo <guohanjun@...wei.com>
> > Reviewed-by: Hanjun Guo <guohanjun@...wei.com>
> 
> Thanks for giving it a go. Catalin, can you queue this via the arm64 tree?

Done. Thanks for the quick fix.

-- 
Catalin