[xen staging] x86/boot: Drop incorrect mapping at l2_xenmap[0]

[patchbot@xxxxxxx]

commit a15b143a5f1c20dc6893bc3e50873e308ef61d87
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Nov 29 16:09:08 2021 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Dec 2 20:02:55 2021 +0000

    x86/boot: Drop incorrect mapping at l2_xenmap[0]
    
    It has been 4 years since the default load address changed from 1M to 2M, 
and
    _stext ceased residing in l2_xenmap[0].  We should not be inserting an 
unused
    mapping.
    
    To ensure we don't create mappings accidentally, loop from 0 and obey
    _PAGE_PRESENT on all entries.
    
    Fixes: 7ed93f3a0dff ("x86: change default load address from 1 MiB to 2 MiB")
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/setup.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index da47cdea14..6f24104842 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1279,16 +1279,12 @@ void __init noreturn __start_xen(unsigned long mbi_p)
 
             /* The only data mappings to be relocated are in the Xen area. */
             pl2e = __va(__pa(l2_xenmap));
-            /*
-             * Undo the temporary-hooking of the l1_directmap.  __2M_text_start
-             * is contained in this PTE.
-             */
+
             BUG_ON(using_2M_mapping() &&
                    l2_table_offset((unsigned long)_erodata) ==
                    l2_table_offset((unsigned long)_stext));
-            *pl2e++ = l2e_from_pfn(xen_phys_start >> PAGE_SHIFT,
-                                   PAGE_HYPERVISOR_RX | _PAGE_PSE);
-            for ( i = 1; i < L2_PAGETABLE_ENTRIES; i++, pl2e++ )
+
+            for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++, pl2e++ )
             {
                 unsigned int flags;
 
--
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