Re: [PATCH v2] hw/arm/virt-acpi-build: Fix IORT id_count

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jun 18, 2024 at 12:04:20PM -0700, Nicolin Chen wrote:
> On Tue, Jun 18, 2024 at 05:49:58AM -0400, Michael S. Tsirkin wrote:
> > On Mon, Jun 17, 2024 at 03:39:45PM -0700, Nicolin Chen wrote:
> > > The IORT doc defines "Number of IDs" ("id_count" in the virt-acpi-build)
> > > to be "the number of IDs in the range minus one". Otherwise, Linux kernel
> > > reports "conflicting mapping for input ID" FW_BUG at the overlapped ID.
> > >
> > > Fixes: 42e0f050e3a5 ("hw/arm/virt-acpi-build: Add IORT support to bypass SMMUv3")
> > > Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> > > ---
> > > Changelog
> > > v2:
> > >  * Moved "-1" to the same line of id_count calculation
> > >  * Added "+1" to the next_range.input_base calculation
> > > v1:
> > >  https://lore.kernel.org/all/20240613234802.828265-1-nicolinc@nvidia.com/
> > >
> > >  hw/arm/virt-acpi-build.c | 9 ++++++---
> > >  1 file changed, 6 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> > > index c3ccfef026..631f2c6d04 100644
> > > --- a/hw/arm/virt-acpi-build.c
> > > +++ b/hw/arm/virt-acpi-build.c
> > > @@ -243,7 +243,8 @@ iort_host_bridges(Object *obj, void *opaque)
> > >
> > >              AcpiIortIdMapping idmap = {
> > >                  .input_base = min_bus << 8,
> > > -                .id_count = (max_bus - min_bus + 1) << 8,
> > > +                /* id_count is the number of IDs in the range minus one */
> > > +                .id_count = ((max_bus - min_bus + 1) << 8) - 1,
> > >              };
> > >              g_array_append_val(idmap_blob, idmap);
> > >          }
> > > @@ -298,11 +299,13 @@ build_iort(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > >              idmap = &g_array_index(smmu_idmaps, AcpiIortIdMapping, i);
> > >
> > >              if (next_range.input_base < idmap->input_base) {
> > > -                next_range.id_count = idmap->input_base - next_range.input_base;
> > > +                /* id_count is the number of IDs in the range minus one */
> > > +                next_range.id_count = idmap->input_base -
> > > +                                      next_range.input_base - 1;
> > >                  g_array_append_val(its_idmaps, next_range);
> > 
> > 
> > What about other places where id_count is set?
> 
> There are only three places where id_count could be set:
> hw/arm/virt-acpi-build.c:296:                .id_count = ((max_bus - min_bus + 1) << 8) - 1,
> hw/arm/virt-acpi-build.c:422:                next_range.id_count = idmap->input_base -
> hw/arm/virt-acpi-build.c:435:            next_range.id_count = 0xFFFF - next_range.input_base;
> 
> This patch fixes two, while the last one is correct using 0xFFFF.
> 
> > >              }
> > >
> > > -            next_range.input_base = idmap->input_base + idmap->id_count;
> > > +            next_range.input_base = idmap->input_base + idmap->id_count + 1;
> > >          }
> > >
> > 
> > Given this was different previously, did you actually test with multiple ranges?
> 
> Tested by creating 5 buses: input_base increases by 0x400 while
> id_count=0x2ff (0x300 - 1). ITS results look correct to me:
> --------------build_iort: smmu_idmaps
> DEBUG: build_iort_id_mapping: input_base=0xec00, id_count=0x2ff, out_ref=0x48, flags=0
> DEBUG: build_iort_id_mapping: input_base=0xf000, id_count=0x2ff, out_ref=0xa0, flags=0
> DEBUG: build_iort_id_mapping: input_base=0xf400, id_count=0x2ff, out_ref=0xf8, flags=0
> DEBUG: build_iort_id_mapping: input_base=0xf800, id_count=0x2ff, out_ref=0x150, flags=0
> DEBUG: build_iort_id_mapping: input_base=0xfc00, id_count=0x2ff, out_ref=0x1a8, flags=0
> --------------build_iort: its_idmaps
> DEBUG: build_iort_id_mapping: input_base=0x0, id_count=0xebff, out_ref=0x30, flags=0
> DEBUG: build_iort_id_mapping: input_base=0xef00, id_count=0xff, out_ref=0x30, flags=0
> DEBUG: build_iort_id_mapping: input_base=0xf300, id_count=0xff, out_ref=0x30, flags=0
> DEBUG: build_iort_id_mapping: input_base=0xf700, id_count=0xff, out_ref=0x30, flags=0
> DEBUG: build_iort_id_mapping: input_base=0xfb00, id_count=0xff, out_ref=0x30, flags=0
> DEBUG: build_iort_id_mapping: input_base=0xff00, id_count=0xff, out_ref=0x30, flags=0
> 
> Thanks
> Nicolin

Okay. Is it the case that none of these effect the IORT in
./tests/data/acpi/virt/IORT then?

-- 
MST