linux-kernel - Re: [RFC v2 2/5] acpi: HMAT support in acpi_parse_entries

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Message-ID: <CAJZ5v0gUA4d+NFqEdsXPVktXf+2AX9MurEQAiCFGxU_eaoYE5A@mail.gmail.com>
Date:   Fri, 7 Jul 2017 00:13:54 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Anaczkowski, Lukasz" <lukasz.anaczkowski@...el.com>,
        "Box, David E" <david.e.box@...el.com>,
        "Kogut, Jaroslaw" <Jaroslaw.Kogut@...el.com>,
        "Lahtinen, Joonas" <joonas.lahtinen@...el.com>,
        "Moore, Robert" <robert.moore@...el.com>,
        "Nachimuthu, Murugasamy" <murugasamy.nachimuthu@...el.com>,
        "Odzioba, Lukasz" <lukasz.odzioba@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "Schmauss, Erik" <erik.schmauss@...el.com>,
        "Verma, Vishal L" <vishal.l.verma@...el.com>,
        "Zheng, Lv" <lv.zheng@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jerome Glisse <jglisse@...hat.com>,
        Len Brown <lenb@...nel.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "devel@...ica.org" <devel@...ica.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
Subject: Re: [RFC v2 2/5] acpi: HMAT support in acpi_parse_entries_array()

On Thu, Jul 6, 2017 at 11:52 PM, Ross Zwisler
<ross.zwisler@...ux.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@...ux.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