From: Roger Pau Monne <roger.pau@citrix.com>
Date: Wed, 22 Jun 2022 12:26:48 +0000 (+0200)
Subject: x86/Kconfig: add selection of default x2APIC destination mode
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=5e296b138eb87be6f1fe334bad69f89fd26fce37;p=people%2Froyger%2Fxen.git

x86/Kconfig: add selection of default x2APIC destination mode

Allow selecting the default x2APIC destination mode from Kconfig.
Note the default destination mode is still Logical (Cluster) mode.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 1e31edc99f..f560dc13f4 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -226,6 +226,35 @@ config XEN_ALIGN_2M
 
 endchoice
 
+choice
+	prompt "x2APIC default destination mode"
+	default X2APIC_LOGICAL
+	---help---
+	  Specify default destination mode for x2APIC.
+
+	  If unsure, choose "Logical".
+
+config X2APIC_LOGICAL
+	bool "Logical mode"
+	---help---
+	  Use Logical Destination mode.
+
+	  When using this mode APICs are addressed using the Logical
+	  Destination mode, which allows for optimized IPI sending,
+	  but also reduces the amount of vectors available for external
+	  interrupts when compared to physical mode.
+
+config X2APIC_PHYS
+	bool "Physical mode"
+	---help---
+	  Use Physical Destination mode.
+
+	  When using this mode APICs are addressed using the Physical
+	  Destination mode, which allows using all dynamic vectors on
+	  each CPU independently.
+
+endchoice
+
 config GUEST
 	bool
 
diff --git a/xen/arch/x86/genapic/x2apic.c b/xen/arch/x86/genapic/x2apic.c
index de5032f202..4b9bbe2f3e 100644
--- a/xen/arch/x86/genapic/x2apic.c
+++ b/xen/arch/x86/genapic/x2apic.c
@@ -228,7 +228,7 @@ static struct notifier_block x2apic_cpu_nfb = {
    .notifier_call = update_clusterinfo
 };
 
-static s8 __initdata x2apic_phys = -1; /* By default we use logical cluster mode. */
+static int8_t __initdata x2apic_phys = -1;
 boolean_param("x2apic_phys", x2apic_phys);
 
 const struct genapic *__init apic_x2apic_probe(void)
@@ -241,7 +241,9 @@ const struct genapic *__init apic_x2apic_probe(void)
          * the usage of the high 16 bits to hold the cluster ID.
          */
         x2apic_phys = !iommu_intremap ||
-                      (acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL);
+                      (acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL) ||
+                      (IS_ENABLED(CONFIG_X2APIC_PHYS) &&
+                       !(acpi_gbl_FADT.flags & ACPI_FADT_APIC_CLUSTER));
     }
     else if ( !x2apic_phys )
         switch ( iommu_intremap )