[Qemu-devel] [PATCH v2 7/7] intel-iommu: keep buggy EIM enabled in 2.7 machine type

["Radim Krčmář" <rkrcmar@redhat.com>]

QEMU 2.7 allowed EIM even in configurations that were forbidden in the
last patch because they were not working, like old KVM or userspace
APIC.  In order to keep backward compatibility, we again allow guests to
misbehave in non-obvious ways, and make it the default.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
 hw/i386/intel_iommu.c | 6 +++++-
 hw/i386/pc_q35.c      | 2 ++
 include/hw/i386/pc.h  | 2 ++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index b1afe5b133e0..d6657a361ff9 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -2458,6 +2458,7 @@ static AddressSpace *vtd_host_dma_iommu(PCIBus *bus, void *opaque, int devfn)
 static void vtd_realize(DeviceState *dev, Error **errp)
 {
     PCMachineState *pcms = PC_MACHINE(qdev_get_machine());
+    PCMachineClass *pcmc = PC_MACHINE_CLASS(MACHINE_GET_CLASS(pcms));
     PCIBus *bus = pcms->bus;
     IntelIOMMUState *s = INTEL_IOMMU_DEVICE(dev);
     X86IOMMUState *x86_iommu = X86_IOMMU_DEVICE(dev);
@@ -2481,11 +2482,14 @@ static void vtd_realize(DeviceState *dev, Error **errp)
     if (s->intr_eim == ON_OFF_AUTO_AUTO && !x86_iommu->intr_supported) {
         s->intr_eim = ON_OFF_AUTO_OFF;
     }
+    if (s->intr_eim == ON_OFF_AUTO_AUTO && pcmc->buggy_intel_iommu_eim) {
+        s->intr_eim = ON_OFF_AUTO_ON;
+    }
     if (s->intr_eim == ON_OFF_AUTO_AUTO) {
         s->intr_eim = kvm_irqchip_in_kernel() ? ON_OFF_AUTO_ON
                                               : ON_OFF_AUTO_OFF;
     }
-    if (s->intr_eim == ON_OFF_AUTO_ON) {
+    if (s->intr_eim == ON_OFF_AUTO_ON && !pcmc->buggy_intel_iommu_eim) {
         if (kvm_irqchip_in_kernel() && !kvm_enable_x2apic()) {
             error_report("intel-iommu,eim=on requires support on the KVM side "
                          "(X2APIC_API, first shipped in v4.7).");
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index 0b214f24c977..97f419fbf4dd 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -304,8 +304,10 @@ DEFINE_Q35_MACHINE(v2_8, "pc-q35-2.8", NULL,
 
 static void pc_q35_2_7_machine_options(MachineClass *m)
 {
+    PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
     pc_q35_2_8_machine_options(m);
     m->alias = NULL;
+    pcmc->buggy_intel_iommu_eim = true;
     SET_MACHINE_COMPAT(m, PC_COMPAT_2_7);
 }
 
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 47bdf10cfd9b..4bd435f8fa5c 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -143,6 +143,8 @@ struct PCMachineClass {
     bool save_tsc_khz;
     /* generate legacy CPU hotplug AML */
     bool legacy_cpu_hotplug;
+    /* enable buggy Intel-IOMMU EIM by default */
+    bool buggy_intel_iommu_eim;
 };
 
 #define TYPE_PC_MACHINE "generic-pc-machine"
-- 
2.10.0