Re: [PATCH v6 15/18] ACPI / APEI: Only use queued estatus entry during _in_nmi_notify_one()

Borislav Petkov
2018-10-12T17:34:35Z

On Fri, Sep 21, 2018 at 11:17:02PM +0100, James Morse wrote:
> Each struct ghes has an worst-case sized buffer for storing the
> estatus. If an error is being processed by ghes_proc() in process
> context this buffer will be in use. If the error source then triggers
> an NMI-like notification, the same buffer will be used by
> _in_nmi_notify_one() to stage the estatus data, before
> __process_error() copys it into a queued estatus entry.
>
> Merge __process_error()s work into _in_nmi_notify_one() so that
> the queued estatus entry is used from the beginning. Use the
> ghes_peek_estatus() so we know how much memory to allocate from
> the ghes_estatus_pool before we read the records.
>
> Reported-by: Borislav Petkov <bp@suse.de>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> drivers/acpi/apei/ghes.c | 45 ++++++++++++++++++++--------------------
> 1 file changed, 22 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index 055176ed68ac..a0c10b60ad44 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -722,40 +722,32 @@ static void ghes_print_queued_estatus(void)
> }
> }
>
> -/* Save estatus for further processing in IRQ context */
> -static void __process_error(struct ghes *ghes,
> - struct acpi_hest_generic_status *ghes_estatus)
> +static int _in_nmi_notify_one(struct ghes *ghes, int fixmap_idx)
> {
> + u64 buf_paddr;
> + int sev, rc = 0;
> u32 len, node_len;
> struct ghes_estatus_node *estatus_node;
> struct acpi_hest_generic_status *estatus;

Please sort function local variables declaration in a reverse christmas
tree order:

<type> longest_variable_name;
<type> shorter_var_name;
<type> even_shorter;
<type> i;

>
> - if (ghes_estatus_cached(ghes_estatus))
> - return;
> + rc = ghes_peek_estatus(ghes, fixmap_idx, &buf_paddr, &len);

Oh ok, maybe not prefix it with "__" - we're using it somewhere else.

> + if (rc)
> + return rc;
>
> - len = cper_estatus_len(ghes_estatus);
> node_len = GHES_ESTATUS_NODE_LEN(len);
>
> estatus_node = (void *)gen_pool_alloc(ghes_estatus_pool, node_len);
> if (!estatus_node)
> - return;
> + return -ENOMEM;
>
> estatus_node->ghes = ghes;
> estatus_node->generic = ghes->generic;
> estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
> - memcpy(estatus, ghes_estatus, len);
> - llist_add(&estatus_node->llnode, &ghes_estatus_llist);
> -}
> -
> -static int _in_nmi_notify_one(struct ghes *ghes, int fixmap_idx)
> -{
> - int sev;
> - u64 buf_paddr;
> - struct acpi_hest_generic_status *estatus = ghes->estatus;
>
> - if (ghes_read_estatus(ghes, estatus, &buf_paddr, fixmap_idx)) {
> + if (__ghes_read_estatus(estatus, buf_paddr, len, fixmap_idx)) {
> ghes_clear_estatus(estatus, buf_paddr, fixmap_idx);
> - return -ENOENT;
> + rc = -ENOENT;
> + goto no_work;
> }
>
> sev = ghes_severity(estatus->error_severity);
> @@ -764,13 +756,20 @@ static int _in_nmi_notify_one(struct ghes *ghes, int fixmap_idx)
> __ghes_panic(ghes, estatus);
> }
>
> - if (!buf_paddr)
> - return 0;
> -
> - __process_error(ghes, estatus);
> ghes_clear_estatus(estatus, buf_paddr, fixmap_idx);
>
> - return 0;
> + if (!buf_paddr || ghes_estatus_cached(estatus))
> + goto no_work;
> +
> + llist_add(&estatus_node->llnode, &ghes_estatus_llist);
> +
> + return rc;
> +
> +no_work:
> + gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node,
> + node_len);

Yeah, let it stick out.

--
Regards/Gruss,
Boris.

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