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

[Marc Zyngier]

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:
>>> Hi Marc,
>>>
>>> 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@xxxxxxx>
>> 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@xxxxxxxxxx>
>> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
>> ---
> 
> 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@xxxxxxxxxx>
> Reviewed-by: Hanjun Guo <guohanjun@xxxxxxxxxx>

Thanks for giving it a go. Catalin, can you queue this via the arm64 tree?

Thanks,

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