[Xen-devel] Fix off-by-one comparison when using apic_flat mode

[Andrew Jones <drjones@xxxxxxxxxx>]

This patch fixes an off-by-one error in the genapic code so that apic_flat
is only used when the maximum APIC ID is less than 8, not also 8 (9 IDs).

Without this patch the kernel may hang when it attempts to process interrupts,
if there are exactly 9 cpus assigned.

Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
---
 arch/x86_64/kernel/genapic-xen.c |  2 +-
 arch/x86_64/kernel/genapic.c     |  2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86_64/kernel/genapic-xen.c b/arch/x86_64/kernel/genapic-xen.c
--- a/arch/x86_64/kernel/genapic-xen.c
+++ b/arch/x86_64/kernel/genapic-xen.c
@@ -85,7 +85,7 @@
                   we have ACPI platform support for CPU hotplug
                   we should detect hotplug capablity from ACPI tables and
                   only do this when really needed. -AK */
-               if (max_apic <= 8)
+               if (max_apic < 8)
                        genapic = &apic_flat;
 #endif
                goto print;
diff --git a/arch/x86_64/kernel/genapic.c b/arch/x86_64/kernel/genapic.c
--- a/arch/x86_64/kernel/genapic.c
+++ b/arch/x86_64/kernel/genapic.c
@@ -79,7 +79,7 @@
                   we have ACPI platform support for CPU hotplug
                   we should detect hotplug capablity from ACPI tables and
                   only do this when really needed. -AK */
-               if (max_apic <= 8)
+               if (max_apic < 8)
                        genapic = &apic_flat;
 #endif
                goto print;

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel