[Xen-devel] [PATCH V12 4/5] p2m: Always use hostp2m when clipping rangesets

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

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@xxxxxxxxxx>
Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
Tested-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>

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

---
Changes since V11:
 - Added end_exclusive, to avoid modifying function arguments.
 - Moved the if ( start >= host_max_pfn ) warning below the code
   doing the clipping.
 - Modified the "Always clip the rangeset down to the host p2m"
   comment to clarify potential issues and remind us to come
   back to it and fix it for good.
---
 xen/arch/x86/mm/p2m.c | 52 +++++++++++++++++++++++++++++++++------------------
 1 file changed, 34 insertions(+), 18 deletions(-)

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index d145850..f552fd5 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1002,30 +1002,46 @@ 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_exclusive) from ot to nt. */
 static void change_type_range(struct p2m_domain *p2m,
-                              unsigned long start, unsigned long end,
+                              unsigned long start, unsigned long end_exclusive,
                               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;
+    unsigned long end = end_exclusive - 1;
     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);
+    /*
+     * Always clip the rangeset down to the host p2m. This is probably not
+     * the right behavior. This should be revisited later, but for now post a
+     * warning.
+     */
+    if ( unlikely(end > host_max_pfn) )
+        end = host_max_pfn;
+
+    if ( start >= host_max_pfn )
+        printk(XENLOG_G_WARNING "Dom%d logdirty rangeset clipped to 
max_mapped_pfn\n",
+               d->domain_id);
+
+    /* 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_exclusive, ot, nt);
         domain_crash(d);
     }
 
@@ -1033,11 +1049,11 @@ 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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