[XEN PATCH v2] x86/apic: Fix signed shift in io_apic.c

[Matthew Barnes <matthew.barnes@xxxxxxxxx>]

There exists bitshifts in the IOAPIC code where signed integers are
shifted to the left by up to 31 bits, which is undefined behaviour.

This patch fixes this by changing the integers from signed to unsigned.

Signed-off-by: Matthew Barnes <matthew.barnes@xxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Changes in v2:
- Correct signed shifting in mask_and_ack_level_ioapic_irq()
- Adjust bracket spacing to uphold Xen style
- Improve commit message
---
 xen/arch/x86/io_apic.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index b48a64246548..d9070601a26f 100644
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -1692,7 +1692,7 @@ static void cf_check mask_and_ack_level_ioapic_irq(struct 
irq_desc *desc)
        !io_apic_level_ack_pending(desc->irq))
         move_masked_irq(desc);
 
-    if ( !(v & (1 << (i & 0x1f))) ) {
+    if ( !(v & (1U << (i & 0x1f))) ) {
         spin_lock(&ioapic_lock);
         __edge_IO_APIC_irq(desc->irq);
         __level_IO_APIC_irq(desc->irq);
@@ -1756,7 +1756,7 @@ static void cf_check end_level_ioapic_irq_new(struct 
irq_desc *desc, u8 vector)
          !io_apic_level_ack_pending(desc->irq) )
         move_native_irq(desc);
 
-    if (!(v & (1 << (i & 0x1f)))) {
+    if ( !(v & (1U << (i & 0x1f))) ) {
         spin_lock(&ioapic_lock);
         __mask_IO_APIC_irq(desc->irq);
         __edge_IO_APIC_irq(desc->irq);
-- 
2.34.1