[PATCH] x86/ioapic: Check 1k alignment for IO-APIC physical addresses

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The MP spec requires a minimum of 1k alignment.  So too does Xen's use of a
single fixmap page to map the IO-APIC.

Reject out-of-spec values so we don't end up in a position where a bad
firmware value causes Xen to use the wrong mapping.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/io_apic.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index 0ef61fb2f167..db1ea6e2f2ca 100644
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -2589,10 +2589,11 @@ static void __init ioapic_init_mappings(void)
         union IO_APIC_reg_01 reg_01;
         paddr_t ioapic_phys = mp_ioapics[i].mpc_apicaddr;
 
-        if ( !ioapic_phys )
+        if ( !ioapic_phys || (ioapic_phys & (KB(1) - 1)) )
         {
             printk(KERN_ERR
-                   "WARNING: bogus zero IO-APIC address found in MPTABLE, 
disabling IO/APIC support!\n");
+                   "WARNING: bogus IO-APIC address %08lx found in MPTABLE, 
disabling IO/APIC support!\n",
+                   ioapic_phys);
             smp_found_config = false;
             skip_ioapic_setup = true;
             break;
-- 
2.30.2