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

[Wei Liu <wl@xxxxxxx>]

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]".

Wei.


> Jan

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