xen/x2apic: enable x2apic mode when supported for HVM

There's no point in disabling x2APIC mode when running as a Xen HVM
guest, just enable it when available.

Remove some unneeded wrapping around the detection functions, and
simply provide a xen_x2apic_available helper that's a wrapper around
x2apic_supported.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20220121090146.13697-1-roger.pau@citrix.com
Signed-off-by: Juergen Gross <jgross@suse.com>

Author: royger

arch/x86/include/asm/xen/hypervisor.h

@@ -43,20 +43,6 @@ static inline uint32_t xen_cpuid_base(void)
 	return hypervisor_cpuid_base("XenVMMXenVMM", 2);
 }
 
-#ifdef CONFIG_XEN
-extern bool __init xen_hvm_need_lapic(void);
-
-static inline bool __init xen_x2apic_para_available(void)
-{
-	return xen_hvm_need_lapic();
-}
-#else
-static inline bool __init xen_x2apic_para_available(void)
-{
-	return (xen_cpuid_base() != 0);
-}
-#endif
-
 struct pci_dev;
 
 #ifdef CONFIG_XEN_PV_DOM0

arch/x86/xen/enlighten_hvm.c

@@ -9,6 +9,7 @@
 #include <xen/events.h>
 #include <xen/interface/memory.h>
 
+#include <asm/apic.h>
 #include <asm/cpu.h>
 #include <asm/smp.h>
 #include <asm/io_apic.h>
@@ -242,15 +243,9 @@ static __init int xen_parse_no_vector_callback(char *arg)
 }
 early_param("xen_no_vector_callback", xen_parse_no_vector_callback);
 
-bool __init xen_hvm_need_lapic(void)
+static __init bool xen_x2apic_available(void)
 {
-	if (xen_pv_domain())
-		return false;
-	if (!xen_hvm_domain())
-		return false;
-	if (xen_feature(XENFEAT_hvm_pirqs) && xen_have_vector_callback)
-		return false;
-	return true;
+	return x2apic_supported();
 }
 
 static __init void xen_hvm_guest_late_init(void)
@@ -312,7 +307,7 @@ struct hypervisor_x86 x86_hyper_xen_hvm __initdata = {
 	.detect                 = xen_platform_hvm,
 	.type			= X86_HYPER_XEN_HVM,
 	.init.init_platform     = xen_hvm_guest_init,
-	.init.x2apic_available  = xen_x2apic_para_available,
+	.init.x2apic_available  = xen_x2apic_available,
 	.init.init_mem_mapping	= xen_hvm_init_mem_mapping,
 	.init.guest_late_init	= xen_hvm_guest_late_init,
 	.runtime.pin_vcpu       = xen_pin_vcpu,