RE: [Intel-wired-lan] [PATCH] i40e: reduce stack usage in i40e_set_fc

[Bowers, AndrewX]

> -----Original Message-----
> From: Intel-wired-lan [mailto:intel-wired-lan-bounces@xxxxxxxxxx] On
> Behalf Of Arnd Bergmann
> Sent: Monday, July 15, 2019 5:35 AM
> To: Kirsher, Jeffrey T <jeffrey.t.kirsher@xxxxxxxxx>; David S. Miller
> <davem@xxxxxxxxxxxxx>
> Cc: Catherine Sullivan <catherine.sullivan@xxxxxxxxx>; Dziggel, Douglas A
> <douglas.a.dziggel@xxxxxxxxx>; Arnd Bergmann <arnd@xxxxxxxx>;
> netdev@xxxxxxxxxxxxxxx; Patryk Małek <patryk.malek@xxxxxxxxx>; linux-
> kernel@xxxxxxxxxxxxxxx; Azarewicz, Piotr <piotr.azarewicz@xxxxxxxxx>;
> Loktionov, Aleksandr <aleksandr.loktionov@xxxxxxxxx>; clang-built-
> linux@xxxxxxxxxxxxxxxx; intel-wired-lan@xxxxxxxxxxxxxxxx; Marczak, Piotr
> <piotr.marczak@xxxxxxxxx>
> Subject: [Intel-wired-lan] [PATCH] i40e: reduce stack usage in i40e_set_fc
> 
> The functions i40e_aq_get_phy_abilities_resp() and i40e_set_fc() both have
> giant structure on the stack, which makes each one use stack frames larger
> than 500 bytes.
> 
> As clang decides one function into the other, we get a warning for exceeding
> the frame size limit on 32-bit architectures:
> 
> drivers/net/ethernet/intel/i40e/i40e_common.c:1654:23: error: stack frame
> size of 1116 bytes in function 'i40e_set_fc' [-Werror,-Wframe-larger-than=]
> 
> When building with gcc, the inlining does not happen, but i40e_set_fc() calls
> i40e_aq_get_phy_abilities_resp() anyway, so they add up on the kernel
> stack just as much.
> 
> The parts that actually use large stacks don't overlap, so make sure each one
> is a separate function, and mark them as noinline_for_stack to prevent the
> compilers from combining them again.
> 
> Fixes: 0a862b43acc6 ("i40e/i40evf: Add module_types and
> update_link_info")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_common.c | 91 +++++++++++--------
>  1 file changed, 51 insertions(+), 40 deletions(-)

Tested-by: Andrew Bowers <andrewx.bowers@xxxxxxxxx>