xen: add the direct mapping area for ISA bus access

add the direct mapping area for ISA bus access when running as initial
domain

Signed-off-by: Juan Quintela <quintela@redhat.com>
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>

3 files changed, 28 insertions, 0 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 1ccfa1bf0f89..9efb00446250 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1186,6 +1186,7 @@ asmlinkage void __init xen_start_kernel(void)
 
         xen_raw_console_write("mapping kernel into physical memory\n");
         pgd = xen_setup_kernel_pagetable(pgd, xen_start_info->nr_pages);
+        xen_ident_map_ISA();
 
         init_mm.pgd = pgd;
 
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index ffc5e24a53ba..eed9c7cee4b7 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1682,6 +1682,7 @@ static void *m2v(phys_addr_t maddr)
         return __ka(m2p(maddr));
 }
 
+/* Set the page permissions on an identity-mapped pages */
 static void set_page_prot(void *addr, pgprot_t prot)
 {
         unsigned long pfn = __pa(addr) >> PAGE_SHIFT;
@@ -1929,6 +1930,29 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
 #endif
 }
 
+__init void xen_ident_map_ISA(void)
+{
+        unsigned long pa;
+
+        /*
+         * If we're dom0, then linear map the ISA machine addresses into
+         * the kernel's address space.
+         */
+        if (!xen_initial_domain())
+                return;
+
+        xen_raw_printk("Xen: setup ISA identity maps\n");
+
+        for (pa = ISA_START_ADDRESS; pa < ISA_END_ADDRESS; pa += PAGE_SIZE) {
+                pte_t pte = mfn_pte(PFN_DOWN(pa), PAGE_KERNEL_IO);
+
+                if (HYPERVISOR_update_va_mapping(PAGE_OFFSET + pa, pte, 0))
+                        BUG();
+        }
+
+        xen_flush_tlb();
+}
+
 static __init void xen_post_allocator_init(void)
 {
         pv_mmu_ops.set_pte = xen_set_pte;
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index c413132702f7..62ceb7864017 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -119,6 +119,9 @@ char * __init xen_memory_setup(void)
          * Even though this is normal, usable memory under Xen, reserve
          * ISA memory anyway because too many things think they can poke
          * about in there.
+         *
+         * In a dom0 kernel, this region is identity mapped with the
+         * hardware ISA area, so it really is out of bounds.
          */
         e820_add_region(ISA_START_ADDRESS, ISA_END_ADDRESS - ISA_START_ADDRESS,
                         E820_RESERVED);