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Diffstat (limited to 'gitlab/issues_text/target_missing/host_missing/accel_missing/2705')
| -rw-r--r-- | gitlab/issues_text/target_missing/host_missing/accel_missing/2705 | 17 |
1 files changed, 0 insertions, 17 deletions
diff --git a/gitlab/issues_text/target_missing/host_missing/accel_missing/2705 b/gitlab/issues_text/target_missing/host_missing/accel_missing/2705 deleted file mode 100644 index 2d2b7cb70..000000000 --- a/gitlab/issues_text/target_missing/host_missing/accel_missing/2705 +++ /dev/null @@ -1,17 +0,0 @@ -USB event delivery does not work correctly for macOS guests with XHCI controller without MSI(-X) -Steps to reproduce: -1. Get a macOS VM working. Either on x86-64 with a Q35 machine type, AppleSMC device, and OpenCore bootloader, or on aarch64 using the patch set and instructions linked above. -2. On x86-64, switch to a NEC XHCI controller with MSI and MSI-X support forcibly disabled: `-device nec-usb-xhci,id=xhci,msi=off,msix=off` -3. Boot macOS. - -USB events are now extremely laggy. A USB keyboard or mouse becomes almost unusable. - - -While narrowing down the problem, I established the following facts by experimentation, tracing, and code inspection: - - * Although the vmapple platform uses an emulated XHCI PCI device for connecting virtual USB devices, it does not support message-signalled interrupts, in either the MSI or MSI-X persuasion. (This is true in Apple's implementation as well, but the macOS guest's XHCI driver unsurprisingly does work with Apple's PCI/XHCI implementation.) - * macOS guests (and the iBoot bootloader) appear to refuse to drive XHCI controllers with `numintrs < 4`, for both aarch64 and x86-64 architectures. They will generally set up event rings 0, 1, and 2. - * QEMU's PCI XHCI implementation does not appear to implement (as of 9.2.0-rc2) any mitigations for when the controller is used in pin-based IRQ mode. It will happily attempt to use event rings >0 in this case, but interrupts are dropped. - * Linux and FreeBSD guests appear to use only interrupter 0 anyway, so these are not useful references. - -It's not entirely clear to me what component is ultimately responsible for the failure here - I suspect there might be some not-quite-right behaviour in both macOS's XHCI driver and Qemu's XHCI implementation, and that these conspire to a non-functional setup. |