From c87759ce876a7a0b17c2bf4f0b964bd51f0ee871 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Tue, 14 May 2019 14:14:41 -0600 Subject: q35: Revert to kernel irqchip Commit b2fc91db8447 ("q35: set split kernel irqchip as default") changed the default for the pc-q35-4.0 machine type to use split irqchip, which turned out to have disasterous effects on vfio-pci INTx support. KVM resampling irqfds are registered for handling these interrupts, but these are non-functional in split irqchip mode. We can't simply test for split irqchip in QEMU as userspace handling of this interrupt is a significant performance regression versus KVM handling (GeForce GPUs assigned to Windows VMs are non-functional without forcing MSI mode or re-enabling kernel irqchip). The resolution is to revert the change in default irqchip mode in the pc-q35-4.1 machine and create a pc-q35-4.0.1 machine for the 4.0-stable branch. The qemu-q35-4.0 machine type should not be used in vfio-pci configurations for devices requiring legacy INTx support without explicitly modifying the VM configuration to use kernel irqchip. Link: https://bugs.launchpad.net/qemu/+bug/1826422 Fixes: b2fc91db8447 ("q35: set split kernel irqchip as default") Signed-off-by: Alex Williamson Reviewed-by: Peter Xu Message-Id: <155786484688.13873.6037015630912983760.stgit@gimli.home> Signed-off-by: Paolo Bonzini --- hw/core/machine.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'hw/core/machine.c') diff --git a/hw/core/machine.c b/hw/core/machine.c index 16ba667434..f1a0f45f9c 100644 --- a/hw/core/machine.c +++ b/hw/core/machine.c @@ -24,6 +24,9 @@ #include "hw/pci/pci.h" #include "hw/mem/nvdimm.h" +GlobalProperty hw_compat_4_0_1[] = {}; +const size_t hw_compat_4_0_1_len = G_N_ELEMENTS(hw_compat_4_0_1); + GlobalProperty hw_compat_4_0[] = {}; const size_t hw_compat_4_0_len = G_N_ELEMENTS(hw_compat_4_0); -- cgit v1.2.3-55-g7522