[+cc Alex] On Fri, Apr 09, 2021 at 11:26:33AM +0200, Ingmar Klein wrote: > Edit: Retry, as I did not consider, that my mail-client would make this > party html. > > Dear maintainers, > I recently encountered an issue on my Proxmox server system, that > includes a Qualcomm QCA6174 m.2 PCIe wifi module. > https://deviwiki.com/wiki/AIRETOS_AFX-QCA6174-NX > > On system boot and subsequent virtual machine start (with passed-through > QCA6174), the VM would just freeze/hang, at the point where the ath10k > driver loads. > Quick search in the proxmox related topics, brought me to the following > discussion, which suggested a PCI quirk entry for the QCA6174 in the kernel: > https://forum.proxmox.com/threads/pcie-passthrough-freezes-proxmox.27513/ > > I then went ahead, got the Proxmox kernel source (v5.4.106) and applied > the attached patch. > Effect was as hoped, that the VM hangs are now gone. System boots and > runs as intended. > > Judging by the existing quirk entries for Atheros, I would think, that > my proposed "fix" could be included in the vanilla kernel. > As far as I saw, there is no entry yet, even in the latest kernel sources. This would need a signed-off-by; see https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?id=v5.11#n361 This is an old issue, and likely we'll end up just applying this as yet another quirk. But looking at c3e59ee4e766 ("PCI: Mark Atheros AR93xx to avoid bus reset"), where it started, it seems to be connected to 425c1b223dac ("PCI: Add Virtual Channel to save/restore support"). I'd like to dig into that a bit more to see if there are any clues. AFAIK Linux itself still doesn't use VC at all, and 425c1b223dac added a fair bit of code. I wonder if we're restoring something out of order or making some simple mistake in the way to restore VC config. > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c > index 706f27a86a8e..ecfe80ec5b9c 100644 > --- a/drivers/pci/quirks.c > +++ b/drivers/pci/quirks.c > @@ -3584,6 +3584,7 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0032, quirk_no_bus_reset); > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x003c, quirk_no_bus_reset); > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0033, quirk_no_bus_reset); > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0034, quirk_no_bus_reset); > +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x003e, quirk_no_bus_reset); > > /* > * Root port on some Cavium CN8xxx chips do not successfully complete a bus
