x86/xen: mark boot CPU of PV guest in MSR_IA32_APICBASE

Recent topology checks of the x86 boot code uncovered the need for PV guests to have the boot cpu marked in the APICBASE MSR. Fixes: 9d22c96 ("x86/topology: Handle bogus ACPI tables correctly") Reported-by: Niels Dettenbach <[email protected]> Signed-off-by: Juergen Gross <[email protected]> Reviewed-by: Thomas Gleixner <[email protected]> Signed-off-by: Juergen Gross <[email protected]>
elodin-sys · Oct 8, 2024 · bf56c41 · bf56c41
1 parent 9af4821
commit bf56c41
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
@@ -1032,6 +1032,10 @@ static u64 xen_do_read_msr(unsigned int msr, int *err)
 	switch (msr) {
 	case MSR_IA32_APICBASE:
 		val &= ~X2APIC_ENABLE;
+		if (smp_processor_id() == 0)
+			val |= MSR_IA32_APICBASE_BSP;
+		else
+			val &= ~MSR_IA32_APICBASE_BSP;
 		break;
 	}
 	return val;