Re: [PATCH v3] ACPI/IORT: Remove erroneous id_count check in iort_node_get_rmr_info()

[Hanjun Guo]

On 2023/7/18 16:56, Shameerali Kolothum Thodi wrote:
> > [+Catalin, Will, Shameer]
> >
> > On Mon, Jul 17, 2023 at 07:33:45PM +0800, Guanghui Feng wrote:
> > > According to the ARM IORT specifications DEN 0049 issue E,
> > > the "Number of IDs" field in the ID mapping format reports
> > > the number of IDs in the mapping range minus one.
> > >
> > > In iort_node_get_rmr_info(), we erroneously skip ID mappings
> > > whose "Number of IDs" equal to 0, resulting in valid mapping
> > > nodes with a single ID to map being skipped, which is wrong.
> > >
> > > Fix iort_node_get_rmr_info() by removing the bogus id_count
> > > check.
> > >
> > > Fixes: 491cf4a6735a ("ACPI/IORT: Add support to retrieve IORT RMR
> > reserved regions")
> > > Signed-off-by: Guanghui Feng<guanghuifeng@xxxxxxxxxxxxxxxxx>
> > > ---
> > >   drivers/acpi/arm64/iort.c | 3 ---
> > >   1 file changed, 3 deletions(-)
> > >
> > > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> > > index 3631230..56d8873 100644
> > > --- a/drivers/acpi/arm64/iort.c
> > > +++ b/drivers/acpi/arm64/iort.c
> > > @@ -1007,9 +1007,6 @@ static void iort_node_get_rmr_info(struct
> > acpi_iort_node *node,
> > >   	for (i = 0; i < node->mapping_count; i++, map++) {
> > >   		struct acpi_iort_node *parent;
> > >
> > > -		if (!map->id_count)
> > > -			continue;
> > > -
> > >   		parent = ACPI_ADD_PTR(struct acpi_iort_node, iort_table,
> > >   				      map->output_reference);
> > >   		if (parent != iommu)
> > Shameer, I know this may look like overkill since the hunk we are
> > removing is buggy but can you please test this patch on platforms
> > with RMR to make sure we are not triggering regressions by removing
> > it (by the specs that's what should be done but current firmware
> > is always something to reckon with) ?
> Yes, that is a valid fix. Unlikely it will be a problem. Anyway, I have requested
> Hanjun to help with the testing as I don't have a test setup with me now.

Valid fix for me as well, we had a firmware bug which reported the
numbers of ID as 1 when we only have one ID mapping, so remove the
check is fine for the old firmware, but to make it sure, we need some
test before give it a pass.

> Hanjun, please help.

I need some time to get it properly tested on two versions of firmware,
and get the test machine properly setup, please allow me give the
feedback next week.

Thanks
Hanjun