[Qemu-devel] [PATCH 2/2] intel-iommu: restrict EIM to quirkless KVM

["Radim Krčmář" <rkrcmar@redhat.com>]

APIC in QEMU doesn't support x2APIC so exposing EIM is pointless and KVM
has a quirk that needs to be disabled unless we want x2APIC message with
destination 0xff to be misinterpreted as a broadcast.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
 hw/i386/intel_iommu.c  | 10 +++++++++-
 target-i386/kvm-stub.c |  5 +++++
 target-i386/kvm.c      | 12 ++++++++++++
 target-i386/kvm_i386.h |  1 +
 4 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 28c31a2cdfa3..733751923233 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -31,6 +31,7 @@
 #include "hw/i386/x86-iommu.h"
 #include "hw/pci-host/q35.h"
 #include "sysemu/kvm.h"
+#include "kvm_i386.h"
 
 /*#define DEBUG_INTEL_IOMMU*/
 #ifdef DEBUG_INTEL_IOMMU
@@ -2364,7 +2365,14 @@ static void vtd_init(IntelIOMMUState *s)
     s->ecap = VTD_ECAP_QI | VTD_ECAP_IRO;
 
     if (x86_iommu->intr_supported) {
-        s->ecap |= VTD_ECAP_IR | VTD_ECAP_EIM | VTD_ECAP_MHMV;
+        s->ecap |= VTD_ECAP_IR | VTD_ECAP_MHMV;
+        /* QEMU APIC does not support x2APIC and KVM does not work well without
+         * disabling a quirk.  IOMMU is unmigratable so we unconditionally use
+         * optional KVM features.
+         */
+        if (kvm_irqchip_in_kernel() && kvm_disable_x2apic_broadcast_quirk()) {
+            s->ecap |= VTD_ECAP_EIM;
+        }
     }
 
     vtd_reset_context_cache(s);
diff --git a/target-i386/kvm-stub.c b/target-i386/kvm-stub.c
index cdf15061091d..71be0bd94ddc 100644
--- a/target-i386/kvm-stub.c
+++ b/target-i386/kvm-stub.c
@@ -25,6 +25,11 @@ bool kvm_has_smm(void)
     return 1;
 }
 
+bool kvm_disable_x2apic_broadcast_quirk(void)
+{
+    return false;
+}
+
 /* This function is only called inside conditionals which we
  * rely on the compiler to optimize out when CONFIG_KVM is not
  * defined.
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 0b2016a77a3c..050c850d77d3 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -128,6 +128,18 @@ bool kvm_allows_irq0_override(void)
     return !kvm_irqchip_in_kernel() || kvm_has_gsi_routing();
 }
 
+static bool kvm_x2apic_api_set_flags(uint64_t flags)
+{
+    KVMState *s = KVM_STATE(current_machine->accelerator);
+
+    return !kvm_vm_enable_cap(s, KVM_CAP_X2APIC_API, 0, flags);
+}
+
+bool kvm_disable_x2apic_broadcast_quirk(void)
+{
+    return kvm_x2apic_api_set_flags(KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK);
+}
+
 static int kvm_get_tsc(CPUState *cs)
 {
     X86CPU *cpu = X86_CPU(cs);
diff --git a/target-i386/kvm_i386.h b/target-i386/kvm_i386.h
index 42b00af1b1c3..1bc445d59c83 100644
--- a/target-i386/kvm_i386.h
+++ b/target-i386/kvm_i386.h
@@ -41,4 +41,5 @@ int kvm_device_msix_set_vector(KVMState *s, uint32_t dev_id, uint32_t vector,
 int kvm_device_msix_assign(KVMState *s, uint32_t dev_id);
 int kvm_device_msix_deassign(KVMState *s, uint32_t dev_id);
 
+bool kvm_disable_x2apic_broadcast_quirk(void);
 #endif
-- 
2.9.2