On 02/28/2018 02:55 PM, Bjorn Helgaas wrote:
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 <garsilva@xxxxxxxxxxxxxx>
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 <garsilva@xxxxxxxxxxxxxx>
[bhelgaas: changelog]
Signed-off-by: Bjorn Helgaas <helgaas@xxxxxxxxxx>
Thanks, Bjorn.
--
Gustavo
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
---
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
