Re: [PATCH] lib/logic_pio: Fix overlap check for pio registery

[John Garry]

On 21/12/2020 03:24, Jiahui Cen wrote:
> Hi John,
>
> On 2020/12/18 18:40, John Garry wrote:
> > On 18/12/2020 06:23, Jiahui Cen wrote:
> > > Since the [start, end) is a half-open interval, a range with the end equal
> > > to the start of another range should not be considered as overlapped.
> > >
> > > Signed-off-by: Jiahui Cen<cenjiahui@xxxxxxxxxx>
> > > ---
> > >    lib/logic_pio.c | 2 +-
> > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/lib/logic_pio.c b/lib/logic_pio.c
> > > index f32fe481b492..445d611f1dc1 100644
> > > --- a/lib/logic_pio.c
> > > +++ b/lib/logic_pio.c
> > > @@ -57,7 +57,7 @@ int logic_pio_register_range(struct logic_pio_hwaddr *new_range)
> > >                new_range->flags == LOGIC_PIO_CPU_MMIO) {
> > >                /* for MMIO ranges we need to check for overlap */
> > >                if (start >= range->hw_start + range->size ||
> > > -                end < range->hw_start) {
> > > +                end <= range->hw_start) {
> > It looks like your change is correct, but should not really have an impact in practice since:
> > a: BIOSes generally list ascending IO port CPU addresses
> > b. there is space between IO port CPU address regions
> >
> > Have you seen a problem here?
> No serious problem. I found it just when I was working on adding support of
> pci expander bridge for Arm in QEMU. I found the IO window of some extended
> root bus could not be registered when I inserted the extended buses' _CRS
> info into DSDT table in the x86 way, which does not sort the buses.
>
> Though root buses should be sorted in QEMU, would it be better to accept
> those non-ascending IO windows?

ok, so it seems that you have seen a real problem, and this issue is not 
just detected by code analysis.

> BTW, for b, it seems to be no space between IO windows of different root buses
> generated by EDK2. Or maybe I missed something obvious.

I don't know about that. Anyway, your change looks ok.

Reviewed-by: John Garry <john.garry@xxxxxxxxxx>

BTW, for your virt env, will there be requirement to unregister PCI MMIO 
ranges? Currently we don't see that in non-virt world.

Thanks,
John