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由 Alex Williamson 提交于
Backport of QEMU v4.1 commit for stable v4.0.1 release commit c87759ce Author: Alex Williamson <alex.williamson@redhat.com> Date: Tue May 14 14:14:41 2019 -0600 q35: Revert to kernel irqchip Commit b2fc91db ("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: b2fc91db ("q35: set split kernel irqchip as default") Cc: qemu-stable@nongnu.org Reviewed-by: NPeter Xu <peterx@redhat.com> Signed-off-by: NAlex Williamson <alex.williamson@redhat.com> (upstream commit c87759ce) Reviewed-by: NMichael S. Tsirkin <mst@redhat.com> *add comments regarding AML mismatch warnings from tests/bios-tables-test.c Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>
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