[PATCH] iscsi_ibft: Fix finding the iBFT under Xen Dom 0

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

Since firmware doesn't indicate the iBFT in the E820, add a reserved
region so that it gets identity mapped when running as Dom 0 so that it
is possible to search for it. Move the call to reserve_ibft_region()
later so that it is called after the Xen identity mapping adjustments
are applied.

Finally, instead of using isa_bus_to_virt() which doesn't do the right
thing under Xen, use early_memremap() like the dmi_scan code does.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---

It tested this to work under Xen and native Linux.

 arch/x86/kernel/setup.c            |  2 +-
 arch/x86/xen/setup.c               |  8 +++++++-
 drivers/firmware/iscsi_ibft_find.c | 24 +++++++++++++++++-------
 3 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 16babff771bd..616b80507abd 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -796,7 +796,6 @@ static void __init early_reserve_memory(void)
 
        memblock_x86_reserve_range_setup_data();
 
-       reserve_ibft_region();
        reserve_bios_regions();
        trim_snb_memory();
 }
@@ -1032,6 +1031,7 @@ void __init setup_arch(char **cmdline_p)
        if (efi_enabled(EFI_BOOT))
                efi_init();
 
+       reserve_ibft_region();
        dmi_setup();
 
        /*
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index c2be3efb2ba0..daab59df3b99 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -772,8 +772,14 @@ char * __init xen_memory_setup(void)
         * UNUSABLE regions in domUs are not handled and will need
         * a patch in the future.
         */
-       if (xen_initial_domain())
+       if (xen_initial_domain()) {
                xen_ignore_unusable();
+               /* Reserve 0.5 MiB to 1 MiB region so iBFT can be found */
+               xen_e820_table.entries[xen_e820_table.nr_entries].addr = 
0x80000;
+               xen_e820_table.entries[xen_e820_table.nr_entries].size = 
0x80000;
+               xen_e820_table.entries[xen_e820_table.nr_entries].type = 
E820_TYPE_RESERVED;
+               xen_e820_table.nr_entries++;
+       }
 
        /* Make sure the Xen-supplied memory map is well-ordered. */
        e820__update_table(&xen_e820_table);
diff --git a/drivers/firmware/iscsi_ibft_find.c 
b/drivers/firmware/iscsi_ibft_find.c
index 94b49ccd23ac..e3c1449987dd 100644
--- a/drivers/firmware/iscsi_ibft_find.c
+++ b/drivers/firmware/iscsi_ibft_find.c
@@ -52,9 +52,9 @@ static const struct {
  */
 void __init reserve_ibft_region(void)
 {
-       unsigned long pos;
+       unsigned long pos, virt_pos = 0;
        unsigned int len = 0;
-       void *virt;
+       void *virt = NULL;
        int i;
 
        ibft_phys_addr = 0;
@@ -70,13 +70,20 @@ void __init reserve_ibft_region(void)
                 * so skip that area */
                if (pos == VGA_MEM)
                        pos += VGA_SIZE;
-               virt = isa_bus_to_virt(pos);
+
+               /* Map page by page */
+               if (offset_in_page(pos) == 0) {
+                       if (virt)
+                               early_memunmap(virt, PAGE_SIZE);
+                       virt = early_memremap_ro(pos, PAGE_SIZE);
+                       virt_pos = pos;
+               }
 
                for (i = 0; i < ARRAY_SIZE(ibft_signs); i++) {
-                       if (memcmp(virt, ibft_signs[i].sign, IBFT_SIGN_LEN) ==
-                           0) {
+                       if (memcmp(virt + (pos - virt_pos), ibft_signs[i].sign,
+                                  IBFT_SIGN_LEN) == 0) {
                                unsigned long *addr =
-                                   (unsigned long *)isa_bus_to_virt(pos + 4);
+                                   (unsigned long *)(virt + pos - virt_pos + 
4);
                                len = *addr;
                                /* if the length of the table extends past 1M,
                                 * the table cannot be valid. */
@@ -84,9 +91,12 @@ void __init reserve_ibft_region(void)
                                        ibft_phys_addr = pos;
                                        memblock_reserve(ibft_phys_addr, 
PAGE_ALIGN(len));
                                        pr_info("iBFT found at %pa.\n", 
&ibft_phys_addr);
-                                       return;
+                                       goto out;
                                }
                        }
                }
        }
+
+out:
+       early_memunmap(virt, PAGE_SIZE);
 }
-- 
2.31.1