[RFC PATCH v2 28/44] i386/tdx: Force x2apic mode and routing for TDs

[isaku . yamahata]

From: Sean Christopherson <sean.j.christopherson@intel.com>

TDX requires x2apic and "resets" vCPUs to have x2apic enabled.  Model
this in QEMU and unconditionally enable x2apic interrupt routing.

This fixes issues where interrupts from IRQFD would not get forwarded to
the guest due to KVM silently dropping the invalid routing entry.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
 hw/intc/apic_common.c           | 12 ++++++++++++
 include/hw/i386/apic.h          |  1 +
 include/hw/i386/apic_internal.h |  1 +
 target/i386/kvm/tdx.c           |  7 +++++++
 4 files changed, 21 insertions(+)

diff --git a/hw/intc/apic_common.c b/hw/intc/apic_common.c
index 2a20982066..b95fed95da 100644
--- a/hw/intc/apic_common.c
+++ b/hw/intc/apic_common.c
@@ -262,6 +262,15 @@ void apic_designate_bsp(DeviceState *dev, bool bsp)
     }
 }
 
+void apic_force_x2apic(DeviceState *dev)
+{
+    if (dev == NULL) {
+        return;
+    }
+
+    APIC_COMMON(dev)->force_x2apic = true;
+}
+
 static void apic_reset_common(DeviceState *dev)
 {
     APICCommonState *s = APIC_COMMON(dev);
@@ -270,6 +279,9 @@ static void apic_reset_common(DeviceState *dev)
 
     bsp = s->apicbase & MSR_IA32_APICBASE_BSP;
     s->apicbase = APIC_DEFAULT_ADDRESS | bsp | MSR_IA32_APICBASE_ENABLE;
+    if (s->force_x2apic) {
+        s->apicbase |= MSR_IA32_APICBASE_EXTD;
+    }
     s->id = s->initial_apic_id;
 
     apic_reset_irq_delivered();
diff --git a/include/hw/i386/apic.h b/include/hw/i386/apic.h
index da1d2fe155..7d05abd7e0 100644
--- a/include/hw/i386/apic.h
+++ b/include/hw/i386/apic.h
@@ -19,6 +19,7 @@ void apic_init_reset(DeviceState *s);
 void apic_sipi(DeviceState *s);
 void apic_poll_irq(DeviceState *d);
 void apic_designate_bsp(DeviceState *d, bool bsp);
+void apic_force_x2apic(DeviceState *d);
 int apic_get_highest_priority_irr(DeviceState *dev);
 
 /* pc.c */
diff --git a/include/hw/i386/apic_internal.h b/include/hw/i386/apic_internal.h
index c175e7e718..eda0b5a587 100644
--- a/include/hw/i386/apic_internal.h
+++ b/include/hw/i386/apic_internal.h
@@ -187,6 +187,7 @@ struct APICCommonState {
     DeviceState *vapic;
     hwaddr vapic_paddr; /* note: persistence via kvmvapic */
     bool legacy_instance_id;
+    bool force_x2apic;
 };
 
 typedef struct VAPICState {
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index c348626dbf..47a502051c 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -139,6 +139,11 @@ int tdx_kvm_init(ConfidentialGuestSupport *cgs, Error 
**errp)
     tdx_caps->nr_cpuid_configs = TDX1_MAX_NR_CPUID_CONFIGS;
     tdx_ioctl(KVM_TDX_CAPABILITIES, 0, tdx_caps);
 
+    if (!kvm_enable_x2apic()) {
+        error_report("Failed to enable x2apic in KVM");
+        exit(1);
+    }
+
     qemu_add_machine_init_done_late_notifier(&tdx_machine_done_late_notify);
 
     return 0;
@@ -296,6 +301,8 @@ void tdx_post_init_vcpu(CPUState *cpu)
 
     hob = tdx_get_hob_entry(tdx);
     _tdx_ioctl(cpu, KVM_TDX_INIT_VCPU, 0, (void *)hob->address);
+
+    apic_force_x2apic(X86_CPU(cpu)->apic_state);
 }
 
 static bool tdx_guest_get_debug(Object *obj, Error **errp)
-- 
2.25.1