RE: slow xp hibernation revisited

["James Harper" <james.harper@bendigoit.com.au>]

> 
> On 04/06/2011 08:38, "James Harper" <james.harper@bendigoit.com.au>
wrote:
> 
> > Looking past the test_bit call, the next statement does another test
and
> > sets last_address_index to 0 and returns NULL. Is this just to
ensure
> > that the next access isn't just trivially accepted?
> 
> Yes, first test is on a potentially stale bucket. Second test is on a
fresh
> bucket.
> 

How about the following patch? Is munmap the correct way to unmap or is
an IOCTL required too?

The exit condition is what would happen anyway after the remap is done
and the page is still invalid.

diff --git a/hw/xen_machine_fv.c b/hw/xen_machine_fv.c
index d02e23f..1ff80bb 100644
--- a/hw/xen_machine_fv.c
+++ b/hw/xen_machine_fv.c
@@ -151,6 +151,24 @@ uint8_t *qemu_map_cache(target_phys_addr_t
phys_addr, uint8_t lock)
         pentry->next = entry;
         qemu_remap_bucket(entry, address_index);
     } else if (!entry->lock) {
+        if (entry->vaddr_base && entry->paddr_index == address_index &&
!test_bit(address_offset>>XC_PAGE_SHIFT, entry->valid_mapping))
+        {
+            /* The page was invalid previously. Test if it is valid now
and only remap if so */
+            xen_pfn_t pfn;
+            int err;
+            void *tmp_vaddr;
+
+            pfn = phys_addr >> XC_PAGE_SHIFT;
+            tmp_vaddr = xc_map_foreign_bulk(xc_handle, domid,
PROT_READ|PROT_WRITE, &pfn, &err, 1);
+            if (tmp_vaddr)
+                munmap(tmp_vaddr, PAGE_SIZE);
+
+            if (!tmp_vaddr || err)
+            {
+                last_address_index = ~0UL;
+                return NULL;
+            }
+        }
         if (!entry->vaddr_base || entry->paddr_index != address_index
|| !test_bit(address_offset>>XC_PAGE_SHIFT, entry->valid_mapping))
             qemu_remap_bucket(entry, address_index);
     }