Re: [Xen-devel] [PATCH] x86: fix off-by-one error when printing memory ranges

[Jan Beulich <jbeulich@xxxxxxxx>]

On 04.02.2020 18:19, Wei Liu wrote:
> On Tue, Feb 04, 2020 at 06:07:00PM +0100, Jan Beulich wrote:
>> On 04.02.2020 17:55, Wei Liu wrote:
>>> Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>
>>> ---
>>>  xen/arch/x86/e820.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/xen/arch/x86/e820.c b/xen/arch/x86/e820.c
>>> index b9f589cac3..d67387f137 100644
>>> --- a/xen/arch/x86/e820.c
>>> +++ b/xen/arch/x86/e820.c
>>> @@ -94,7 +94,7 @@ static void __init print_e820_memory_map(struct e820entry 
>>> *map, unsigned int ent
>>>      for (i = 0; i < entries; i++) {
>>>          printk(" %016Lx - %016Lx ",
>>>                 (unsigned long long)(map[i].addr),
>>> -               (unsigned long long)(map[i].addr + map[i].size));
>>> +               (unsigned long long)(map[i].addr + map[i].size) - 1);
>>
>> Why was this an error? If we used [,] like Linux does - sure.
>> But we don't. The presentation, without looking at the source,
>> simply leaves open whether this was meant to be [,] or [,).
>> And it continues to be left open with the adjustment made.
>>
> 
> Well, Linux's representation is not what is normally done in math
> either.
> 
> It is like
> 
>   Xen: [mem 0x0000000000000000-0x000000000009efff] usable
> 
> Note it is using '-', not ','. And there is "mem" at the beginning.
> 
> I have always interpreted the [] pair as something to enclose the range,
> not of mathematically meaning.
> 
> If you want, I can change Xen's format string to "[%016Lx, %016Lx]".

I think this would make things less ambiguous, yes. But my primary
request here is to have neither "fix" nor "error" nor anything
alike in the title or description.

Jan

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