[Xen-devel] [PATCH v3 04/10] xen: map a dummy page for local apic and ioapic in xen_set_fixmap

[Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>]

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
 arch/x86/xen/mmu.c |   23 ++++++++++++++++++++---
 1 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 42086ac..ffc5e24 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. */
-- 
1.5.6.5


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