[PATCH v2] kvm: Remove KVM_CREATE_IRQCHIP support assumption

[Andrew Jones <ajones@xxxxxxxxxxxxxxxx>]

Since Linux commit 00f918f61c56 ("RISC-V: KVM: Skeletal in-kernel AIA
irqchip support") checking KVM_CAP_IRQCHIP returns non-zero when the
RISC-V platform has AIA. The cap indicates KVM supports at least one
of the following ioctls:

  KVM_CREATE_IRQCHIP
  KVM_IRQ_LINE
  KVM_GET_IRQCHIP
  KVM_SET_IRQCHIP
  KVM_GET_LAPIC
  KVM_SET_LAPIC

but the cap doesn't imply that KVM must support any of those ioctls
in particular. However, QEMU was assuming the KVM_CREATE_IRQCHIP
ioctl was supported. Stop making that assumption by introducing a
KVM parameter that each architecture which supports KVM_CREATE_IRQCHIP
sets. Adding parameters isn't awesome, but given how the
KVM_CAP_IRQCHIP isn't very helpful on its own, we don't have a lot of
options.

Signed-off-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
---

While this fixes booting guests on riscv KVM with AIA it's unlikely
to get merged before the QEMU support for KVM AIA[1] lands, which
would also fix the issue. I think this patch is still worth considering
though since QEMU's assumption is wrong.

[1] https://lore.kernel.org/all/20230714084429.22349-1-yongxuan.wang@xxxxxxxxxx/

v2:
  - Move the s390x code to an s390x file. [Thomas]
  - Drop the KVM_CAP_IRQCHIP check from the top of kvm_irqchip_create(),
    as it's no longer necessary.

 accel/kvm/kvm-all.c    | 16 ++++------------
 include/sysemu/kvm.h   |  1 +
 target/arm/kvm.c       |  3 +++
 target/i386/kvm/kvm.c  |  2 ++
 target/s390x/kvm/kvm.c | 11 +++++++++++
 5 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 373d876c0580..cddcb6eca641 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -86,6 +86,7 @@ struct KVMParkedVcpu {
 };
 
 KVMState *kvm_state;
+bool kvm_has_create_irqchip;
 bool kvm_kernel_irqchip;
 bool kvm_split_irqchip;
 bool kvm_async_interrupts_allowed;
@@ -2358,17 +2359,6 @@ static void kvm_irqchip_create(KVMState *s)
     int ret;
 
     assert(s->kernel_irqchip_split != ON_OFF_AUTO_AUTO);
-    if (kvm_check_extension(s, KVM_CAP_IRQCHIP)) {
-        ;
-    } else if (kvm_check_extension(s, KVM_CAP_S390_IRQCHIP)) {
-        ret = kvm_vm_enable_cap(s, KVM_CAP_S390_IRQCHIP, 0);
-        if (ret < 0) {
-            fprintf(stderr, "Enable kernel irqchip failed: %s\n", strerror(-ret));
-            exit(1);
-        }
-    } else {
-        return;
-    }
 
     /* First probe and see if there's a arch-specific hook to create the
      * in-kernel irqchip for us */
@@ -2377,8 +2367,10 @@ static void kvm_irqchip_create(KVMState *s)
         if (s->kernel_irqchip_split == ON_OFF_AUTO_ON) {
             error_report("Split IRQ chip mode not supported.");
             exit(1);
-        } else {
+        } else if (kvm_has_create_irqchip) {
             ret = kvm_vm_ioctl(s, KVM_CREATE_IRQCHIP);
+        } else {
+            return;
         }
     }
     if (ret < 0) {
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 115f0cca79d1..84b1bb3dc91e 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -32,6 +32,7 @@
 #ifdef CONFIG_KVM_IS_POSSIBLE
 
 extern bool kvm_allowed;
+extern bool kvm_has_create_irqchip;
 extern bool kvm_kernel_irqchip;
 extern bool kvm_split_irqchip;
 extern bool kvm_async_interrupts_allowed;
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index b4c7654f4980..2fa87b495d68 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -250,6 +250,9 @@ int kvm_arm_get_max_vm_ipa_size(MachineState *ms, bool *fixed_ipa)
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     int ret = 0;
+
+    kvm_has_create_irqchip = kvm_check_extension(s, KVM_CAP_IRQCHIP);
+
     /* For ARM interrupt delivery is always asynchronous,
      * whether we are using an in-kernel VGIC or not.
      */
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index ebfaf3d24c79..6363e67f092d 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -2771,6 +2771,8 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         }
     }
 
+    kvm_has_create_irqchip = kvm_check_extension(s, KVM_CAP_IRQCHIP);
+
     return 0;
 }
 
diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index a9e5880349d9..bcc735227f7d 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -391,6 +391,17 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
     }
 
     kvm_set_max_memslot_size(KVM_SLOT_MAX_BYTES);
+
+    kvm_has_create_irqchip = kvm_check_extension(s, KVM_CAP_S390_IRQCHIP);
+    if (kvm_has_create_irqchip) {
+        int ret = kvm_vm_enable_cap(s, KVM_CAP_S390_IRQCHIP, 0);
+
+        if (ret < 0) {
+            fprintf(stderr, "Enable kernel irqchip failed: %s\n", strerror(-ret));
+            exit(1);
+        }
+    }
+
     return 0;
 }
 
-- 
2.41.0