[Xen-devel] [PATCH] x86/pv: Drop create_pae_xen_mappings()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

This is leftovers from the 32bit hypervisor days.  The only Xen content in
this virtual range for 32bit PV guests is the compat M2P.  It is not critical
that the mapping is present, nor is it critical that the slot is unshared.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
---
 xen/arch/x86/mm.c | 46 ----------------------------------------------
 1 file changed, 46 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index ed77270..3262499 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -1429,46 +1429,6 @@ static int alloc_l1_table(struct page_info *page)
     return ret;
 }
 
-static int create_pae_xen_mappings(struct domain *d, l3_pgentry_t *pl3e)
-{
-    struct page_info *page;
-    l3_pgentry_t     l3e3;
-
-    if ( !is_pv_32bit_domain(d) )
-        return 1;
-
-    pl3e = (l3_pgentry_t *)((unsigned long)pl3e & PAGE_MASK);
-
-    /* 3rd L3 slot contains L2 with Xen-private mappings. It *must* exist. */
-    l3e3 = pl3e[3];
-    if ( !(l3e_get_flags(l3e3) & _PAGE_PRESENT) )
-    {
-        gdprintk(XENLOG_WARNING, "PAE L3 3rd slot is empty\n");
-        return 0;
-    }
-
-    /*
-     * The Xen-private mappings include linear mappings. The L2 thus cannot
-     * be shared by multiple L3 tables. The test here is adequate because:
-     *  1. Cannot appear in slots != 3 because get_page_type() checks the
-     *     PGT_pae_xen_l2 flag, which is asserted iff the L2 appears in slot 3
-     *  2. Cannot appear in another page table's L3:
-     *     a. alloc_l3_table() calls this function and this check will fail
-     *     b. mod_l3_entry() disallows updates to slot 3 in an existing table
-     */
-    page = l3e_get_page(l3e3);
-    BUG_ON(page->u.inuse.type_info & PGT_pinned);
-    BUG_ON((page->u.inuse.type_info & PGT_count_mask) == 0);
-    BUG_ON(!(page->u.inuse.type_info & PGT_pae_xen_l2));
-    if ( (page->u.inuse.type_info & PGT_count_mask) != 1 )
-    {
-        gdprintk(XENLOG_WARNING, "PAE L3 3rd slot is shared\n");
-        return 0;
-    }
-
-    return 1;
-}
-
 static int alloc_l2_table(struct page_info *page, unsigned long type,
                           int preemptible)
 {
@@ -1573,8 +1533,6 @@ static int alloc_l3_table(struct page_info *page)
         adjust_guest_l3e(pl3e[i], d);
     }
 
-    if ( rc >= 0 && !create_pae_xen_mappings(d, pl3e) )
-        rc = -EINVAL;
     if ( rc < 0 && rc != -ERESTART && rc != -EINTR )
     {
         gdprintk(XENLOG_WARNING, "Failure in alloc_l3_table: slot %#x\n", i);
@@ -2120,10 +2078,6 @@ static int mod_l3_entry(l3_pgentry_t *pl3e,
         return -EFAULT;
     }
 
-    if ( likely(rc == 0) )
-        if ( !create_pae_xen_mappings(d, pl3e) )
-            BUG();
-
     put_page_from_l3e(ol3e, pfn, 0, 1);
     return rc;
 }
-- 
2.1.4


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