hw/i386/amd_iommu: Simplify non-KVM checks on XTSup feature

Generic code wanting to access KVM specific methods should
do so being protected by the 'kvm_enabled()' helper.

Doing so avoid link failures when optimization is disabled
(using --enable-debug), see for example commits c04cfb4596
("hw/i386: fix short-circuit logic with non-optimizing builds")
and 0266aef8cd ("amd_iommu: Fix kvm_enable_x2apic link error
with clang in non-KVM builds").

XTSup feature depends on KVM, so protect the whole block
checking the XTSup feature with a check on whether KVM is
enabled.

Since x86_cpus_init() already checks APIC ID > 255 imply
kernel support for irqchip and X2APIC, remove the confuse
and unlikely reachable "AMD IOMMU xtsup=on requires support
on the KVM side" message.

Fix a type in "configuration" in error message.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Message-Id: <20241129155802.35534-1-philmd@linaro.org>

hw/i386/amd_iommu.c

@@ -1652,17 +1652,10 @@ static void amdvi_sysbus_realize(DeviceState *dev, Error **errp)
     memory_region_add_subregion_overlap(&s->mr_sys, AMDVI_INT_ADDR_FIRST,
                                         &s->mr_ir, 1);
 
-    /* AMD IOMMU with x2APIC mode requires xtsup=on */
-    if (x86ms->apic_id_limit > 255 && !s->xtsup) {
-        error_report("AMD IOMMU with x2APIC confguration requires xtsup=on");
+    if (kvm_enabled() && x86ms->apic_id_limit > 255 && !s->xtsup) {
+        error_report("AMD IOMMU with x2APIC configuration requires xtsup=on");
         exit(EXIT_FAILURE);
     }
-    if (s->xtsup) {
-        if (kvm_irqchip_is_split() && !kvm_enable_x2apic()) {
-            error_report("AMD IOMMU xtsup=on requires support on the KVM side");
-            exit(EXIT_FAILURE);
-        }
-    }
 
     pci_setup_iommu(bus, &amdvi_iommu_ops, s);
     amdvi_init(s);