linux-kernel - Re: [PATCH v2] ACPI / extlog: Handle multiple records

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Date:   Thu, 13 Oct 2022 20:44:51 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Tony Luck <tony.luck@...el.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, Borislav Petkov <bp@...en8.de>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev
Subject: Re: [PATCH v2] ACPI / extlog: Handle multiple records

On Mon, Oct 10, 2022 at 10:34 PM Tony Luck <tony.luck@...el.com> wrote:
>
> If there is no user space consumer of extlog_mem trace records, then
> Linux properly handles multiple error records in an ELOG block
>
>         extlog_print()
>           print_extlog_rcd()
>             __print_extlog_rcd()
>               cper_estatus_print()
>                 apei_estatus_for_each_section()
>
> But the other code path hard codes looking for a single record to
> output a trace record.
>
> Fix by using the same apei_estatus_for_each_section() iterator
> to step over all records.
>
> Fixes: 2dfb7d51a61d ("trace, RAS: Add eMCA trace event interface")
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> ---
>
> Changes since v1: Oops. Cut & pasted the apei_estatus_for_each_section()
> line, but forgot to change the argument from "estatus" to "tmp". Need to
> walk the *copy* that was made, not the original because BIOS is allowed to
> stomp on it as soon as it sees block_status has been cleared.
>
>  drivers/acpi/acpi_extlog.c | 33 ++++++++++++++++++++-------------
>  1 file changed, 20 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/acpi/acpi_extlog.c b/drivers/acpi/acpi_extlog.c
> index 72f1fb77abcd..e648158368a7 100644
> --- a/drivers/acpi/acpi_extlog.c
> +++ b/drivers/acpi/acpi_extlog.c
> @@ -12,6 +12,7 @@
>  #include <linux/ratelimit.h>
>  #include <linux/edac.h>
>  #include <linux/ras.h>
> +#include <acpi/ghes.h>
>  #include <asm/cpu.h>
>  #include <asm/mce.h>
>
> @@ -138,8 +139,8 @@ static int extlog_print(struct notifier_block *nb, unsigned long val,
>         int     cpu = mce->extcpu;
>         struct acpi_hest_generic_status *estatus, *tmp;
>         struct acpi_hest_generic_data *gdata;
> -       const guid_t *fru_id = &guid_null;
> -       char *fru_text = "";
> +       const guid_t *fru_id;
> +       char *fru_text;
>         guid_t *sec_type;
>         static u32 err_seq;
>
> @@ -160,17 +161,23 @@ static int extlog_print(struct notifier_block *nb, unsigned long val,
>
>         /* log event via trace */
>         err_seq++;
> -       gdata = (struct acpi_hest_generic_data *)(tmp + 1);
> -       if (gdata->validation_bits & CPER_SEC_VALID_FRU_ID)
> -               fru_id = (guid_t *)gdata->fru_id;
> -       if (gdata->validation_bits & CPER_SEC_VALID_FRU_TEXT)
> -               fru_text = gdata->fru_text;
> -       sec_type = (guid_t *)gdata->section_type;
> -       if (guid_equal(sec_type, &CPER_SEC_PLATFORM_MEM)) {
> -               struct cper_sec_mem_err *mem = (void *)(gdata + 1);
> -               if (gdata->error_data_length >= sizeof(*mem))
> -                       trace_extlog_mem_event(mem, err_seq, fru_id, fru_text,
> -                                              (u8)gdata->error_severity);
> +       apei_estatus_for_each_section(tmp, gdata) {
> +               if (gdata->validation_bits & CPER_SEC_VALID_FRU_ID)
> +                       fru_id = (guid_t *)gdata->fru_id;
> +               else
> +                       fru_id = &guid_null;
> +               if (gdata->validation_bits & CPER_SEC_VALID_FRU_TEXT)
> +                       fru_text = gdata->fru_text;
> +               else
> +                       fru_text = "";
> +               sec_type = (guid_t *)gdata->section_type;
> +               if (guid_equal(sec_type, &CPER_SEC_PLATFORM_MEM)) {
> +                       struct cper_sec_mem_err *mem = (void *)(gdata + 1);
> +
> +                       if (gdata->error_data_length >= sizeof(*mem))
> +                               trace_extlog_mem_event(mem, err_seq, fru_id, fru_text,
> +                                                      (u8)gdata->error_severity);
> +               }
>         }
>
>  out:
> --

Applied as 6.1-rc material, thanks!