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>

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 42086ac406af21da6d281687625684c0dddbe11c..ffc5e24a53ba9689ba15e8ee42f9175b1ab0dbdc 100644 (file)
--- 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;
@@ -1880,9 +1882,6 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
 # endif
 #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:
@@ -1890,6 +1889,22 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
                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. */