Re: [Xen-devel] [PATCH] trace: Fix incorrect number of pages used for trace metadata

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 30/09/16 17:04, Igor Druzhinin wrote:
> On 30/09/16 15:46, George Dunlap wrote:
>> On 29/09/16 14:53, Igor Druzhinin wrote:
>>> As long as t_info_first_offset is calculated in uint32_t offsets we
>>> need to
>>> multiply it by sizeof(uint32_t) in order to get the right number of
>>> pages
>>> for trace metadata. Not doing that makes it impossible to read the trace
>>> buffer correctly from userspace for some corner cases.
>>>
>>> Signed-off-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
>>
>> Hmm, looks like we actually want to revert this c/s fbf96e6, "xentrace:
>> correct formula to calculate t_info_pages".  But that one was presumably
>> written (and Acked by me) because the variable name there,
>> t_info_first_offset, is confusing.
>>
>> The other mistake in fbf96e6 is that before t_info_words was actually
>> denominated in words; but after it's denominated in bytes (which is
>> again confusing).
>>
>> What about something like the attached instead?  This should fix your
>> problem while making the code clearer.
>>
>>  -George
>>
>>
> 
> Reviewed-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>

Thanks.  Any chance I could get a Tested-by as well? :-)

 -George


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