xen: map a dummy page for local apic and ioapic in xen_set_fixmap

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 20 insertions, 3 deletions

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 42086ac406af..ffc5e24a53ba 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1861,6 +1861,8 @@ __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
 }
 #endif  /* CONFIG_X86_64 */
 
+static unsigned char dummy_mapping[PAGE_SIZE] __page_aligned_bss;
+
 static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
 {
         pte_t pte;
@@ -1881,15 +1883,28 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
 #else
         case VSYSCALL_LAST_PAGE ... VSYSCALL_FIRST_PAGE:
 #endif
-#ifdef CONFIG_X86_LOCAL_APIC
-        case FIX_APIC_BASE:     /* maps dummy local APIC */
-#endif
         case FIX_TEXT_POKE0:
         case FIX_TEXT_POKE1:
                 /* All local page mappings */
                 pte = pfn_pte(phys, prot);
                 break;
 
+#ifdef CONFIG_X86_LOCAL_APIC
+        case FIX_APIC_BASE:     /* maps dummy local APIC */
+                pte = pfn_pte(PFN_DOWN(__pa(dummy_mapping)), PAGE_KERNEL);
+                break;
+#endif
+
+#ifdef CONFIG_X86_IO_APIC
+        case FIX_IO_APIC_BASE_0 ... FIX_IO_APIC_BASE_END:
+                /*
+                 * We just don't map the IO APIC - all access is via
+                 * hypercalls.  Keep the address in the pte for reference.
+                 */
+                pte = pfn_pte(PFN_DOWN(__pa(dummy_mapping)), PAGE_KERNEL);
+                break;
+#endif
+
         case FIX_PARAVIRT_BOOTMAP:
                 /* This is an MFN, but it isn't an IO mapping from the
                    IO domain */
@@ -2027,6 +2042,8 @@ void __init xen_init_mmu_ops(void)
         pv_mmu_ops = xen_mmu_ops;
 
         vmap_lazy_unmap = false;
+
+        memset(dummy_mapping, 0xff, PAGE_SIZE);
 }
 
 /* Protected by xen_reservation_lock. */