On Thu, Sep 12, 2024 at 05:01:57PM -0700, Dan Williams wrote: > Nirmal Patel wrote: > > On Thu, 12 Sep 2024 11:10:21 -0700 > > Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > > > > > Manivannan Sadhasivam wrote: > > > [..] > > > > I don't think the issue should be constrained to VMD only. Based on > > > > my conversation with Nirmal [1], I understood that it is SPDK that > > > > makes wrong assumption if the device's PCI_INTERRUPT_LINE is > > > > non-zero (and I assumed that other application could do the same). > > > > > > I am skeptical one can find an example of an application that gets > > > similarly confused. SPDK is not a typical consumer of PCI device > > > information. > > > > > > > In that case, how it can be classified as the "idiosyncracy" of > > > > VMD? > > > > > > If VMD were a typical PCIe switch, firmware would have already fixed > > > up these values. In fact this problem could likely also be fixed in > > > platform firmware, but the history of VMD is to leak workaround after > > > workaround into the kernel. > > > > This is not VMD leaking workaround in kernel, rather the patch is > > trying to keep fix limited to VMD driver. > > Oh, ok, I see that now, however... > > > I tried over 10 different NVMes and only 1 vendor has > > PCI_INTERRUPT_LINE register set to 0xFF. The platform firmware > > doesn't change that with or without VMD. > > ...SPDK is still asserting that it wants to be the NVME host driver in > userspace. As part of that it gets to keep all the pieces and must > realize that a device that has MSI/-X enabled is not using INTx > regardless of that register value. > > Do not force the kernel to abide by SPDK expectations when the PCI core > / Linux-NVME driver contract does not need the PCI_INTERRUPT_LINE > cleared. If SPDK is taking over NVME, it gets to take over *all* of it. In that case, we do not need a fix at all (even for VMD). My initial assumption was that, some other userspace applications may also behave the same way as SPDK. But I agree with you that unless we hear about them, it doesn't warrant a fix in the kernel. Thanks! - Mani -- மணிவண்ணன் சதாசிவம்
