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

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@vger.kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
 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 ?

Regards,
Sudeep

On Tue, Jun 21, 2022 at 9:20 PM Sudeep Holla <sudeep.holla@arm.com> 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@vger.kernel.org
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  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@kernel.org>

> 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
>

Hi Sudeep,

On Tuesday 21 Jun 2022 at 20:20:15 (+0100), Sudeep Holla 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@vger.kernel.org
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  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 ?
> 
> Regards,
> Sudeep
> 
> 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
> 

I've run the set on Kunpeng920 where Dietmar noticed an issue [1] before
and it looks good to me.

Tested-by: Ionela Voinescu <ionela.voinescu@arm.com>

[1]
https://lore.kernel.org/lkml/0bf199a0-251d-323c-974a-bfd4e26f4cce@arm.com/

Thanks,
Ionela.