[Xen-devel] [PATCH] x86/Xen: don't report ancient LAPIC version

["Jan Beulich" <JBeulich@xxxxxxxx>]

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 <jbeulich@xxxxxxxx>

--- a/arch/x86/xen/apic.c
+++ b/arch/x86/xen/apic.c
@@ -57,7 +57,7 @@ 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());




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