Re: [PATCH v3 15/18] arm64: arch_timer: Enable CNTVCT_EL0 trap if workaround is enabled

From: Catalin Marinas <catalin.marinas@arm.com>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: Hanjun Guo <guohanjun@huawei.com>,
	"Lixiaoping (Timmy)" <lixiaoping3@huawei.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	dann frazier <dann.frazier@canonical.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Will Deacon <will.deacon@arm.com>, Scott Wood <oss@buserror.net>,
	Hanjun Guo <hanjun.guo@linaro.org>,
	Dingtianhong <dingtianhong@huawei.com>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v3 15/18] arm64: arch_timer: Enable CNTVCT_EL0 trap if workaround is enabled
Date: Mon, 24 Apr 2017 12:26:38 +0100	[thread overview]
Message-ID: <20170424112638.GA25449@e104818-lin.cambridge.arm.com> (raw)
In-Reply-To: <d7c03009-3b21-0bce-74f5-b11dd359eb97@arm.com>

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@arm.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@huawei.com>
> >> Signed-off-by: Marc Zyngier <marc.zyngier@arm.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@huawei.com>
> > Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
> 
> Thanks for giving it a go. Catalin, can you queue this via the arm64 tree?

Done. Thanks for the quick fix.

-- 
Catalin