[Xen-devel] [PATCH v4 07/10] xen: add the direct mapping area for ISA bus access

[stefano.stabellini@xxxxxxxxxxxxx]

From: Juan Quintela <quintela@xxxxxxxxxx>

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

Signed-off-by: Juan Quintela <quintela@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
 arch/x86/xen/enlighten.c |    1 +
 arch/x86/xen/mmu.c       |   24 ++++++++++++++++++++++++
 arch/x86/xen/setup.c     |    3 +++
 3 files changed, 28 insertions(+), 0 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 1ccfa1b..9efb004 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 ffc5e24..eed9c7c 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 c413132..62ceb78 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);
-- 
1.5.6.5


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