Re: [PATCH RFC] xen/pci: detect when BARs overlap RAM

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Jan 28, 2022 at 07:48:44AM +0100, Jan Beulich wrote:
> On 26.01.2022 16:45, Roger Pau Monné wrote:
> > On Wed, Jan 26, 2022 at 03:08:28PM +0100, Jan Beulich wrote:
> >> On 26.01.2022 13:26, Roger Pau Monne wrote:
> >>> --- a/xen/arch/x86/mm.c
> >>> +++ b/xen/arch/x86/mm.c
> >>> @@ -479,6 +479,26 @@ unsigned int page_get_ram_type(mfn_t mfn)
> >>>      return type ?: RAM_TYPE_UNKNOWN;
> >>>  }
> >>>  
> >>> +bool is_iomem_range(uint64_t start, uint64_t size)
> >>
> >> Might be nice to have this sit next it is_iomem_page(). And wouldn't
> >> at least "start" better be paddr_t?
> > 
> > (paddr_t, size_t) would be better, but AFAICT size_t can be an
> > unsigned long and on Arm32 that won't be suitable for holding a 64bit
> > BAR size.
> 
> Talking of representing the range - a BAR occupying one part of a
> page overlapping an E820 entry covering another part of that same
> page is going to be equally bad, I think. The range may therefore
> want expressing in page granularity. This may then be easier as
> [start,end], at least on the calling side (can use PFN_DOWN()
> twice then).

Yes, indeed, would likely be better. Then I can make both parameters
unsigned long.

I also think is_memory_hole would be a suitable name given the new
implementation?

Thanks, Roger.