This is a suggestion that would really help anyone using trying to use
xhci passthrough on a platform without streams.
** Changed in: qemu
Status: Incomplete => New
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https://bugs.launchpad.net/bugs/1843711
Title:
qemu-xhci device should detect if libusb host supports streams
Status in QEMU:
New
Bug description:
When using USBÂ passthrough with the qemu-xhci (and nec-usb-xhci),
streams are enabled by default, but if the host xHCI controller
doesn't support them, it will trigger hard-to-debug UAS guest errors.
This should be possible to detect since the kernel returns ENOSYS (errno 38)
when xhci host controller does not support streams:
libusb: error [do_streams_ioctl] streams-ioctl failed error -1
errno 38
qemu: libusb_alloc_streams: -99 [OTHER]
Maybe libusb should return a dedicated error instead of
LIBUSB_ERROR_OTHER in this case, but qemu does not handle any other
error code anyway.
Just trying to enable streams before enabling them in qemu should do
it. I don't know if it should be done in hcd-xhci.c, host-libusb.c or
elsewhere, but this would be detectable at launch instead of a static
option true/false, maybe a ternary with auto would be better.
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