[PATCH v5 01/19] ACPI: PPTT: Use table offset as fw_token instead of virtual address

[Sudeep Holla]

There is need to use the cache sharing information quite early during
the boot before the secondary cores are up and running. The permanent
memory map for all the ACPI tables(via acpi_permanent_mmap) is turned
on in acpi_early_init() which is quite late for the above requirement.

As a result there is possibility that the ACPI PPTT gets mapped to
different virtual addresses. In such scenarios, using virtual address as
fw_token before the acpi_permanent_mmap is enabled results in different
fw_token for the same cache entity and hence wrong cache sharing
information will be deduced based on the same.

Instead of using virtual address, just use the table offset as the
unique firmware token for the caches. The same offset is used as
ACPI identifiers if the firmware has not set a valid one for other
entries in the ACPI PPTT.

Link: https://lore.kernel.org/r/20220621192034.3332546-2-sudeep.holla@xxxxxxx
Cc: linux-acpi@xxxxxxxxxxxxxxx
Tested-by: Ionela Voinescu <ionela.voinescu@xxxxxxx>
Acked-by: Rafael J. Wysocki <rafael@xxxxxxxxxx>
Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
---
 drivers/acpi/pptt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index 701f61c01359..763f021d45e6 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -437,7 +437,8 @@ static void cache_setup_acpi_cpu(struct acpi_table_header *table,
 		pr_debug("found = %p %p\n", found_cache, cpu_node);
 		if (found_cache)
 			update_cache_properties(this_leaf, found_cache,
-			                        cpu_node, table->revision);
+						ACPI_TO_POINTER(ACPI_PTR_DIFF(cpu_node, table)),
+						table->revision);
 
 		index++;
 	}
-- 
2.36.1