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.
> 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?
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.
>
> --
> 2.43.0
