linux-kernel - Re: [PATCHv12 7/9] asm-generic/io: Add logging support for MMIO accessors

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Message-ID: <da3c667c-cec3-58d8-b06f-b4e79796a07b@quicinc.com>
Date:   Thu, 28 Apr 2022 17:59:25 +0530
From:   Sai Prakash Ranjan <quic_saipraka@...cinc.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     <arnd@...db.de>, <catalin.marinas@....com>, <rostedt@...dmis.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <maz@...nel.org>, <quic_psodagud@...cinc.com>,
        <quic_tsoni@...cinc.com>, <will@...nel.org>
Subject: Re: [PATCHv12 7/9] asm-generic/io: Add logging support for MMIO
 accessors

On 4/28/2022 5:32 PM, Greg KH wrote:
> On Thu, Apr 28, 2022 at 04:51:49PM +0530, Sai Prakash Ranjan wrote:
>> On 4/28/2022 4:21 PM, Greg KH wrote:
>>> On Thu, Apr 28, 2022 at 03:25:30PM +0530, Sai Prakash Ranjan wrote:
>>>> Add logging support for MMIO high level accessors such as read{b,w,l,q}
>>>> and their relaxed versions to aid in debugging unexpected crashes/hangs
>>>> caused by the corresponding MMIO operation.
>>>>
>>>> Signed-off-by: Sai Prakash Ranjan <quic_saipraka@...cinc.com>
>>>> ---
>>>>    include/asm-generic/io.h | 82 ++++++++++++++++++++++++++++++++++++++--
>>>>    1 file changed, 78 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
>>>> index 7ce93aaf69f8..99090722cb4b 100644
>>>> --- a/include/asm-generic/io.h
>>>> +++ b/include/asm-generic/io.h
>>>> @@ -10,6 +10,7 @@
>>>>    #include <asm/page.h> /* I/O is all done through memory accesses */
>>>>    #include <linux/string.h> /* for memset() and memcpy() */
>>>>    #include <linux/types.h>
>>>> +#include <linux/instruction_pointer.h>
>>>>    #ifdef CONFIG_GENERIC_IOMAP
>>>>    #include <asm-generic/iomap.h>
>>>> @@ -61,6 +62,35 @@
>>>>    #define __io_par(v)     __io_ar(v)
>>>>    #endif
>>>> +#if IS_ENABLED(CONFIG_TRACE_MMIO_ACCESS) && !(defined(__DISABLE_TRACE_MMIO__))
>>> Shouldn't you document __DISABLE_TRACE_MMIO__ somewhere?  It's not even
>>> in the changelog.  Put a big comment above this for what is is for and
>>> how to use it.  Otherwise you will forget all about this in 6 months :)
>>>
>>> thanks,
>>>
>>> greg k-h
>> Didn't you ask me to split the patch to the one actually adding the flag and the one using it.
> Yes, and isn't this the commit that adds the flag?  Or was that on an
> earlier one that I missed?
>
> Ah, it's in patch 6/9
>
> But you should also document it here in the .h file, otherwise the only
> place it is described is in some random kvm Makefile that no one will
> ever notice :)
>
>

Sure it makes sense, will add it.

Thanks,
Sai