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

[Wei Liu <wl@xxxxxxx>]

On Thu, Feb 06, 2020 at 12:38:37PM +0100, Jan Beulich wrote:
> On 06.02.2020 12:34, Wei Liu wrote:
> > On Wed, Feb 05, 2020 at 11:45:39AM +0000, Wei Liu wrote:
> >> On Wed, Feb 05, 2020 at 09:12:50AM +0100, Jan Beulich wrote:
> >>> 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.
> >>
> >> OK. I can certainly change the subject line to
> >>
> >>   x86: subtract 1 when printing e820 ranges
> > 
> > If I hear no further objections I will commit this patch with the above
> > subject line today.
> 
> And with the presentation changed to [,]?

Fine by me too. I will post a new patch shortly.

Wei.

> 
> Jan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel