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

[Borislav Petkov <bp@alien8.de>]

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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