On Mon, Jun 17, 2024 at 06:41:55AM -0400, Michael S. Tsirkin wrote:
> On Thu, Jun 13, 2024 at 04:48:02PM -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 <nicol...@nvidia.com>
> > ---
> > hw/arm/virt-acpi-build.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> > index c3ccfef026..b9343dde0f 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);
> > }
> > @@ -298,7 +299,9 @@ 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) {
> > + /* id_count is the number of IDs in the range minus one */
> > next_range.id_count = idmap->input_base -
> > next_range.input_base;
> > + next_range.id_count -= 1;
>
> I would just add - 1 on the previous line, instead of making it
> incorrect then correcting it.
OK. Let's do this then:
- 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);
> > }
>
>
> But the value is used later:
>
> next_range.input_base = idmap->input_base + idmap->id_count;
>
> Wouldn't that make next_range incorrect?
Ah, missed that. Thanks!
- next_range.input_base = idmap->input_base + idmap->id_count;
+ next_range.input_base = idmap->input_base + idmap->id_count + 1;
>
> I also note that
>
> static void build_iort_id_mapping(GArray *table_data, uint32_t input_base,
> uint32_t id_count, uint32_t out_ref)
> {
> /* Table 4 ID mapping format */
> build_append_int_noprefix(table_data, input_base, 4); /* Input base */
> build_append_int_noprefix(table_data, id_count, 4); /* Number of IDs */
> build_append_int_noprefix(table_data, input_base, 4); /* Output base */
> build_append_int_noprefix(table_data, out_ref, 4); /* Output Reference */
> /* Flags */
> build_append_int_noprefix(table_data, 0 /* Single mapping (disabled) */,
> 4);
> }
>
>
> That comment
> /* Table 4 ID mapping format */
>
> really should be before the function and it should mention the spec
> it's from - specifically the earliest spec including the relevant table.
Well, it's an inline-like function called by build_iort() only,
where there is a function header mentioning the doc.
Should this function have to repeat?
Anyway, that would be a different patch. I'll submit a v2 first.
Thank you
Nicolin
