On Tue, Feb 27, 2018 at 05:19:52PM -0600, Gustavo A. R. Silva wrote:
> It seems that the expression threshold_us * 1000 will never exceed the
> 32-bit limits [1]. So changing the type of threshold_ns from u64 to u32
> seems sensible [2].
>
> [1] https://marc.info/?l=linux-kernel&m=151855021100725&w=2
> [2] https://marc.info/?l=linux-kernel&m=151976318924615&w=2
>
> Addresses-Coverity-ID: 1462501
> Signed-off-by: Gustavo A. R. Silva <garsi...@embeddedor.com>
Applied with Andy's Reviewed-by to pci/aspm for v4.17, thanks!
I included a more detailed analysis in the changelog:
PCI/ASPM: Declare threshold_ns as u32, not u64
aspm_calc_l1ss_info() computes l1_2_threshold in microseconds as:
l1_2_threshold = 2 + 4 + t_common_mode + t_power_on;
where t_common_mode is at most 255us:
PCI_L1SS_CAP_CM_RESTORE_TIME 0x0000ff00 <-- 8 bits; <256us
and t_power_on is at most 31 * 100us = 3100us:
PCI_L1SS_CAP_P_PWR_ON_VALUE 0x00f80000 <-- 5 bits; <32
PCI_L1SS_CAP_P_PWR_ON_SCALE 0x00030000 <-- *2us, *10us, or *100us
So l1_2_threshold is at most 2 + 4 + 255 + 3100 = 3361, which means
threshold_ns is at most 3361 * 1000 = 3361000, which easily fits in a
u32.
Declare threshold_ns as u32, not u64. This fixes a Coverity warning.
Addresses-Coverity-ID: 1462501
Signed-off-by: Gustavo A. R. Silva <garsi...@embeddedor.com>
[bhelgaas: changelog]
Signed-off-by: Bjorn Helgaas <helg...@kernel.org>
Reviewed-by: Andy Shevchenko <andy.shevche...@gmail.com>
> ---
> drivers/pci/pcie/aspm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 57feef2..8633fc4 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -322,7 +322,7 @@ static u32 calc_l1ss_pwron(struct pci_dev *pdev, u32
> scale, u32 val)
>
> static void encode_l12_threshold(u32 threshold_us, u32 *scale, u32 *value)
> {
> - u64 threshold_ns = threshold_us * 1000;
> + u32 threshold_ns = threshold_us * 1000;
>
> /* See PCIe r3.1, sec 7.33.3 and sec 6.18 */
> if (threshold_ns < 32) {
> --
> 2.7.4
>
