[PATCH V11 4/5] p2m: Always use hostp2m when clipping rangesets

[Razvan Cojocaru <rcojocaru@bitdefender.com>]

The logdirty rangesets of the altp2ms need to be kept in sync with the
hostp2m. This means when iterating through the altp2ms, we need to
use the host p2m to clip the rangeset, not the indiviual altp2m's
value.

This change also:

- Documents that the end is non-inclusive

- Calculates an "inclusive" value for the end once, rather than
  open-coding the modification, and (worse) back-modifying updates so
  that the calculation ends up correct

- Clarifies the logic deciding whether to call
  change_entry_type_global() or change_entry_type_range()

- Handles the case where start >= hostp2m->max_mapped_pfn

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
Tested-by: Tamas K Lengyel <tamas@tklengyel.com>

---
CC: George Dunlap <george.dunlap@eu.citrix.com>
CC: Jan Beulich <jbeulich@suse.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: "Roger Pau Monné" <roger.pau@citrix.com>

---
Changes since V10:
 - Fixed a double-space in the patch description.
 - Fixed a coding style issue for
   "if ( !start && end >= p2m->max_mapped_pfn)" (no space before
   closing ')').
 - Switched the early return comment back to "/* If the requested
   range is out of scope, return doing nothing. */.
 - Added Tamas' Tested-by.
---
 xen/arch/x86/mm/p2m.c | 47 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 30 insertions(+), 17 deletions(-)

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index d145850..539ea16 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1002,30 +1002,43 @@ int p2m_change_type_one(struct domain *d, unsigned long gfn_l,
     return rc;
 }
 
-/* Modify the p2m type of a range of gfns from ot to nt. */
+/* Modify the p2m type of [start, end) from ot to nt. */
 static void change_type_range(struct p2m_domain *p2m,
                               unsigned long start, unsigned long end,
                               p2m_type_t ot, p2m_type_t nt)
 {
-    unsigned long gfn = start;
     struct domain *d = p2m->domain;
+    const unsigned long host_max_pfn = p2m_get_hostp2m(d)->max_mapped_pfn;
     int rc = 0;
 
-    if ( unlikely(end > p2m->max_mapped_pfn) )
-    {
-        if ( !gfn )
-        {
-            p2m->change_entry_type_global(p2m, ot, nt);
-            gfn = end;
-        }
-        end = p2m->max_mapped_pfn + 1;
-    }
-    if ( gfn < end )
-        rc = p2m->change_entry_type_range(p2m, ot, nt, gfn, end - 1);
+    --end;
+
+    if ( start >= host_max_pfn )
+        printk(XENLOG_G_WARNING "Dom%d logdirty rangeset clipped to max_mapped_pfn\n",
+               d->domain_id);
+
+    /* Always clip the rangeset down to the host p2m. */
+    if ( unlikely(end > host_max_pfn) )
+        end = host_max_pfn;
+
+    /* If the requested range is out of scope, return doing nothing. */
+    if ( start > end )
+        return;
+
+    /*
+     * If all valid gfns are in the invalidation range, just do a
+     * global type change. Otherwise, invalidate only the range we
+     * need.
+     */
+    if ( !start && end >= p2m->max_mapped_pfn )
+        p2m->change_entry_type_global(p2m, ot, nt);
+    else
+        rc = p2m->change_entry_type_range(p2m, ot, nt, start, end);
+
     if ( rc )
     {
-        printk(XENLOG_G_ERR "Error %d changing Dom%d GFNs [%lx,%lx] from %d to %d\n",
-               rc, d->domain_id, start, end - 1, ot, nt);
+        printk(XENLOG_G_ERR "Error %d changing Dom%d GFNs [%lx,%lx) from %d to %d\n",
+               rc, d->domain_id, start, end, ot, nt);
         domain_crash(d);
     }
 
@@ -1033,11 +1046,11 @@ static void change_type_range(struct p2m_domain *p2m,
     {
     case p2m_ram_rw:
         if ( ot == p2m_ram_logdirty )
-            rc = rangeset_remove_range(p2m->logdirty_ranges, start, end - 1);
+            rc = rangeset_remove_range(p2m->logdirty_ranges, start, end);
         break;
     case p2m_ram_logdirty:
         if ( ot == p2m_ram_rw )
-            rc = rangeset_add_range(p2m->logdirty_ranges, start, end - 1);
+            rc = rangeset_add_range(p2m->logdirty_ranges, start, end);
         break;
     default:
         break;
-- 
2.7.4


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