Hi Bjorn, On 18/06/2021 14:13, Bjorn Helgaas wrote: > [+to Jon, +cc Thierry] > > On Fri, Jun 18, 2021 at 06:34:20PM +0800, kernel test robot wrote: >> tree/branch: https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git for-linus >> branch HEAD: 15ac366c3d20ce1e08173f1de393a8ce95a1facf PCI: aardvark: Fix kernel panic during PIO transfer >> >> possible Warning in current branch: >> >> drivers/pci/controller/dwc/pcie-tegra194.c:1829:23: warning: Shifting signed 32-bit value by 31 bits is undefined behaviour. See condition at line 1826. [shiftTooManyBitsSigned] > > This looks like a legit warning, but I think the only commit that > could be related is this one: > > https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/commit/?h=for-linus&id=99ab5996278379a02d5a84c4a7ac33a2ebfdb29e > > which doesn't touch that code. > > It does *move* some code, so maybe this was an existing warning that > moved enough that the robot thought it was new? I guessing that this is now happening because we are now compiling the bulk of the code in the driver. However, yes looks like it has been there for a while. I wonder if the '(1 << irq)' is being treated as a signed type. > How can we reproduce this to make sure we fix it? I was able to reproduce it by ... $ cppcheck --force --enable=all drivers/pci/controller/dwc/pcie-tegra194.c Checking drivers/pci/controller/dwc/pcie-tegra194.c ... drivers/pci/controller/dwc/pcie-tegra194.c:1829:23: portability: Shifting signed 32-bit value by 31 bits is implementation-defined behaviour. See condition at line 1826. [shiftTooManyBitsSigned] appl_writel(pcie, (1 << irq), APPL_MSI_CTRL_1); ^ drivers/pci/controller/dwc/pcie-tegra194.c:1826:19: note: Assuming that condition 'irq>31' is not redundant if (unlikely(irq > 31)) ^ drivers/pci/controller/dwc/pcie-tegra194.c:1829:23: note: Shift appl_writel(pcie, (1 << irq), APPL_MSI_CTRL_1); I was able to fix this by ... diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c index 8fc08336f76e..05d6a8da190b 100644 --- a/drivers/pci/controller/dwc/pcie-tegra194.c +++ b/drivers/pci/controller/dwc/pcie-tegra194.c @@ -1826,7 +1826,7 @@ static int tegra_pcie_ep_raise_msi_irq(struct tegra_pcie_dw *pcie, u16 irq) if (unlikely(irq > 31)) return -EINVAL; - appl_writel(pcie, (1 << irq), APPL_MSI_CTRL_1); + appl_writel(pcie, (BIT(1) << irq), APPL_MSI_CTRL_1); return 0; } I can send this as a patch. Cheers Jon -- nvpublic
