linux-kernel - Re: [Y2038] [PATCH v2 2/2] ppdev: add support for compat ioctl

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Date:	Wed, 6 Jan 2016 20:56:28 +0800
From:	Bamvor Jian Zhang <bamvor.zhangjian@...aro.org>
To:	Sudip Mukherjee <sudipm.mukherjee@...il.com>,
	Arnd Bergmann <arnd@...db.de>
Cc:	y2038@...ts.linaro.org, gregkh@...uxfoundation.org,
	broonie@...nel.org, linux-kernel@...r.kernel.org,
	Bamvor Zhang Jian <bamvor.zhangjian@...aro.org>
Subject: Re: [Y2038] [PATCH v2 2/2] ppdev: add support for compat ioctl

Hi, Sudip

On 01/04/2016 09:14 PM, Sudip Mukherjee wrote:
> On Sat, Jan 02, 2016 at 11:40:51PM +0100, Arnd Bergmann wrote:
>> On Saturday 02 January 2016 11:59:29 Sudip Mukherjee wrote:
>>>>
>>>> Just to be sure we are talking about the same thing: you mean running a 64-bit
>>>> kernel in a kvm guest with a 32-bit file system, right? Running a 32-bit
>>>> kvm guest on a 64-bit host would not be interesting of course.
>>>
>>> The kvm (actually qemu, started from virt-manager with -enable-kvm) that
>>> I just configured shows the following:
>>>
>>> lscpu shows:
>>>
>>> Architecture:          i686
>>> CPU op-mode(s):        32-bit, 64-bit
>>> Byte Order:            Little Endian
>>> CPU(s):                1
>>> On-line CPU(s) list:   0
>>> Thread(s) per core:    1
>>> Core(s) per socket:    1
>>> Socket(s):             1
>>> Vendor ID:             GenuineIntel
>>> CPU family:            6
>>> Model:                 6
>>> Stepping:              3
>>> CPU MHz:               2993.200
>>> BogoMIPS:              5986.40
>>> Virtualization:        VT-x
>>> Hypervisor vendor:     KVM
>>> Virtualization type:   full
>>> L1d cache:             32K
>>> L1i cache:             32K
>>> L2 cache:              4096K
>>>
>>> uname -i shows:
>>> i686
>>>
>>>
>>> Will it be ok to test in this one?
>>
>>
>> If 'uname -i' reports i686, that usually means you have configured the
>> kernel for 32-bit. Try rebuilding the kernel with 'CONFIG_64BIT' and
>> 'CONFIG_IA32_EMULATION' enabled to test that the 32-bit user space now
>> also works under a 64-bit kernel.
> 
> done... tested with CONFIG_64BIT and CONFIG_IA32_EMULATION. The original
> ppdev code failed with my userspace test code. After applying patch 1/2
> of v3 it still failed, but after applying 2/2 of v3 it worked.
> will you take v3 through your y2038 tree? or I can keep them for,
> ummmmm, 4.6 merge window.
> 
>>
>> That reminds me, we should now remove the code from fs/compat_ioctl.c
>> that was handling emulating the other ioctl commands, the new .compat_ioctl
>> callback in ppdev takes care of that along with the PPGETTIME/PPSETTIME
>> calls, see below
> 
> Bamvor, care to send a patch for these also...
Sure. Should I send this patch with previous two patches in v4 or send this
single patch to Alexander Viro and linux-fsdevel@...r.kernel.org?

Regards

Bamvor
> 
> regards
> sudip
> 
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