Re: [RFC v2 2/5] acpi: HMAT support in acpi_parse_entries_array()

Rafael J. Wysocki
2017-07-06T22:13:57Z

On Thu, Jul 6, 2017 at 11:52 PM, Ross Zwisler
<ross.zwisler@linux.intel.com> wrote:
> The current implementation of acpi_parse_entries_array() assumes that each
> subtable has a standard ACPI subtable entry of type struct
> acpi_sutbable_header. This standard subtable header has a one byte length
> followed by a one byte type.
>
> The HMAT subtables have to allow for a longer length so they have subtable
> headers of type struct acpi_hmat_structure which has a 2 byte type and a 4
> byte length.
>
> Enhance the subtable parsing in acpi_parse_entries_array() so that it can
> handle these new HMAT subtables.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ---
> drivers/acpi/numa.c | 2 +-
> drivers/acpi/tables.c | 52 ++++++++++++++++++++++++++++++++++++++++-----------
> 2 files changed, 42 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/acpi/numa.c b/drivers/acpi/numa.c
> index edb0c79..917f1cc 100644
> --- a/drivers/acpi/numa.c
> +++ b/drivers/acpi/numa.c
> @@ -443,7 +443,7 @@ int __init acpi_numa_init(void)
> * So go over all cpu entries in SRAT to get apicid to node mapping.
> */
>
> - /* SRAT: Static Resource Affinity Table */
> + /* SRAT: System Resource Affinity Table */
> if (!acpi_table_parse(ACPI_SIG_SRAT, acpi_parse_srat)) {
> struct acpi_subtable_proc srat_proc[3];
>

This change is unrelated to the rest of the patch.

Maybe send it separately?

> diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
> index ff42539..7979171 100644
> --- a/drivers/acpi/tables.c
> +++ b/drivers/acpi/tables.c
> @@ -218,6 +218,33 @@ void acpi_table_print_madt_entry(struct acpi_subtable_header *header)
> }
> }
>
> +static unsigned long __init
> +acpi_get_entry_type(char *id, void *entry)
> +{
> + if (!strncmp(id, ACPI_SIG_HMAT, 4))
> + return ((struct acpi_hmat_structure *)entry)->type;
> + else
> + return ((struct acpi_subtable_header *)entry)->type;
> +}

I slightly prefer to use ? : in similar situations.

> +
> +static unsigned long __init
> +acpi_get_entry_length(char *id, void *entry)
> +{
> + if (!strncmp(id, ACPI_SIG_HMAT, 4))
> + return ((struct acpi_hmat_structure *)entry)->length;
> + else
> + return ((struct acpi_subtable_header *)entry)->length;
> +}
> +
> +static unsigned long __init
> +acpi_get_subtable_header_length(char *id)
> +{
> + if (!strncmp(id, ACPI_SIG_HMAT, 4))
> + return sizeof(struct acpi_hmat_structure);
> + else
> + return sizeof(struct acpi_subtable_header);
> +}
> +
> /**
> * acpi_parse_entries_array - for each proc_num find a suitable subtable
> *
> @@ -242,10 +269,10 @@ acpi_parse_entries_array(char *id, unsigned long table_size,
> struct acpi_subtable_proc *proc, int proc_num,
> unsigned int max_entries)
> {
> - struct acpi_subtable_header *entry;
> - unsigned long table_end;
> + unsigned long table_end, subtable_header_length;
> int count = 0;
> int errs = 0;
> + void *entry;
> int i;
>
> if (acpi_disabled)
> @@ -263,19 +290,23 @@ acpi_parse_entries_array(char *id, unsigned long table_size,
> }
>
> table_end = (unsigned long)table_header + table_header->length;
> + subtable_header_length = acpi_get_subtable_header_length(id);
>
> /* Parse all entries looking for a match. */
>
> - entry = (struct acpi_subtable_header *)
> - ((unsigned long)table_header + table_size);
> + entry = (void *)table_header + table_size;
> +
> + while (((unsigned long)entry) + subtable_header_length < table_end) {
> + unsigned long entry_type, entry_length;
>
> - while (((unsigned long)entry) + sizeof(struct acpi_subtable_header) <
> - table_end) {
> if (max_entries && count >= max_entries)
> break;
>
> + entry_type = acpi_get_entry_type(id, entry);
> + entry_length = acpi_get_entry_length(id, entry);
> +
> for (i = 0; i < proc_num; i++) {
> - if (entry->type != proc[i].id)
> + if (entry_type != proc[i].id)
> continue;
> if (!proc[i].handler ||
> (!errs && proc[i].handler(entry, table_end))) {
> @@ -290,16 +321,15 @@ acpi_parse_entries_array(char *id, unsigned long table_size,
> count++;
>
> /*
> - * If entry->length is 0, break from this loop to avoid
> + * If entry_length is 0, break from this loop to avoid
> * infinite loop.
> */
> - if (entry->length == 0) {
> + if (entry_length == 0) {
> pr_err("[%4.4s:0x%02x] Invalid zero length\n", id, proc->id);
> return -EINVAL;
> }
>
> - entry = (struct acpi_subtable_header *)
> - ((unsigned long)entry + entry->length);
> + entry += entry_length;
> }
>
> if (max_entries && count > max_entries) {
> --

The rest is fine by me.

Thanks,
Rafael