x86/Xen: don't report ancient LAPIC version

jbeulich · Boris Ostrovsky · commit 0f3922a9b99e · 2017-12-12T09:39:17.000-05:00
Unconditionally reporting a value seen on the P4 or older invokes
functionality like io_apic_get_unique_id() on 32-bit builds, resulting
in a panic() with sufficiently many CPUs and/or IO-APICs. Doing what
that function does would be the hypervisor's responsibility anyway, so
makes no sense to be used when running on Xen. Uniformly report a more
modern version; this shouldn't matter much as both LAPIC and IO-APIC are
being managed entirely / mostly by the hypervisor.

Signed-off-by: Jan Beulich &lt;jbeulich@suse.com&gt;
Reviewed-by: Juergen Gross &lt;jgross@suse.com&gt;
Signed-off-by: Boris Ostrovsky &lt;boris.ostrovsky@oracle.com&gt;
diff --git a/arch/x86/xen/apic.c b/arch/x86/xen/apic.c
@@ -56,7 +56,7 @@ static u32 xen_apic_read(u32 reg)
 		return 0;
 
 	if (reg == APIC_LVR)
-		return 0x10;
+		return 0x14;
 #ifdef CONFIG_X86_32
 	if (reg == APIC_LDR)
 		return SET_APIC_LOGICAL_ID(1UL << smp_processor_id());
