Re: [PATCH v4 01/20] ACPI: PPTT: Use table offset as fw_token instead of virtual address

[Rafael J. Wysocki]

On Tue, Jun 21, 2022 at 9:20 PM Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
>
> 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.
>
> Cc: linux-acpi@xxxxxxxxxxxxxxx
> Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
> ---
>  drivers/acpi/pptt.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> Hi Rafael,
>
> If you are happy with this change, can you provide Ack, so that it can be
> merged together with other changes ?

No objections:

Acked-by: Rafael J. Wysocki <rafael@xxxxxxxxxx>

> 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
>