Hi Eric,
On 6/17/25 10:22, Eric Auger wrote:
Hi Gustavo,
On 6/16/25 3:18 PM, Gustavo Romero wrote:
The comment about the mapping from SMMU to ITS is incorrect and it reads
"RC -> ITS". The code in question actually maps SMMU -> ITS, so the
mapping in question is not direct. The direct mapping, i.e., RC -> ITS,
is handled a bit further down in the code, in the else block, and we
take the opportunity to update that as well, adding "RC -> ITS" to the
text so it's easier to see it's the direct map to the ITS Group node.
Signed-off-by Gustavo Romero <gustavo.rom...@linaro.org>
---
hw/arm/virt-acpi-build.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index 9eee284c80..6990bce3bb 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -407,23 +407,27 @@ build_iort(GArray *table_data, BIOSLinker *linker,
VirtMachineState *vms)
if (vms->iommu == VIRT_IOMMU_SMMUV3) {
AcpiIortIdMapping *range;
- /* translated RIDs connect to SMMUv3 node: RC -> SMMUv3 -> ITS */
+ /* Map RIDs (input) from RC to SMMUv3 nodes: RC -> SMMUv3. */
yes this is what the code builds at this location.
for (i = 0; i < smmu_idmaps->len; i++) {
range = &g_array_index(smmu_idmaps, AcpiIortIdMapping, i);
- /* output IORT node is the smmuv3 node */
+ /* Output IORT node is the SMMUv3 node. */
build_iort_id_mapping(table_data, range->input_base,
range->id_count, smmu_offset);
}
- /* bypassed RIDs connect to ITS group node directly: RC -> ITS */
+ /* Map DeviceIDs (input) from SMMUv3 to ITS Group nodes: SMMU -> ITS.
*/
But here I am confused. To me the its_idmaps matches the idmap between
RC and ITS. I understand this is built from holes left by bypassed
buses. See the build_iort() implementation. The comment at
ah, thanks! I see. Indeed, it's mapping the RC -> ITS, not the SMMU -> ITS.
I'll fix it in v5.
One thing that confused me, which I think is actually ok, is that the
output ID range from SMMU 0x000-0xFFFF) overlaps the output ID range
from the RC (e.g. 0x100-0xFFFF) because the SMMU output range is defined as
always taking the whole 16-bit range in:
[...]
366 build_append_int_noprefix(table_data, irq + 1, 4); /* PRI */
367 build_append_int_noprefix(table_data, irq + 3, 4); /* GERR */
368 build_append_int_noprefix(table_data, irq + 2, 4); /* Sync */
369 build_append_int_noprefix(table_data, 0, 4); /* Proximity domain
*/
370 /* DeviceID mapping index (ignored since interrupts are GSIV
based) */
371 build_append_int_noprefix(table_data, 0, 4);
372
373 /* output IORT node is the ITS group node (the first node) */
374 build_iort_id_mapping(table_data, 0, 0x10000, IORT_NODE_OFFSET);
<=========== HERE
375 }
376
377 /* Table 17 Root Complex Node */
I think that's ok since ITS can disambiguate the Device IDs from SMMU and from
RC.
/*
* Split the whole RIDs by mapping from RC to SMMU,
* build the ID mapping from RC to ITS directly.
*/
for (i = 0; i < smmu_idmaps->len; i++) {
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;
g_array_append_val(its_idmaps, next_range);
}
next_range.input_base = idmap->input_base + idmap->id_count;
}
is not crystal clear but it looks like filling the holes into its_idmap.
k, I'll create a helper as you suggested in 7/8 to populate the its_idmaps.
> Besides there is another "Its group" instance to be replaced by ITS Group
Pardon, what do you mean? Another text to be replaced or it's just a comment
about the "else" block when smmu is off?
Thanks!
Cheers,
Gustavo
Eric
for (i = 0; i < its_idmaps->len; i++) {
range = &g_array_index(its_idmaps, AcpiIortIdMapping, i);
- /* output IORT node is the ITS group node (the first node) */
+ /* Output IORT node is the ITS Group node (the first node). */
build_iort_id_mapping(table_data, range->input_base,
range->id_count, IORT_NODE_OFFSET);
}
} else {
- /* output IORT node is the ITS group node (the first node) */
+ /*
+ * Map bypassed RIDs (input) (don't go through the SMMU) to ITS Group
+ * nodes: RC -> ITS.
+ * Output IORT node is the ITS Group node (the first node).
+ */
build_iort_id_mapping(table_data, 0, 0x10000, IORT_NODE_OFFSET);
}
