Hi,
On 02/04/2022 00:53, Stefano Stabellini wrote:
On Mon, 21 Feb 2022, Julien Grall wrote:
@@ -1333,21 +1386,34 @@ static int xen_pt_update(unsigned long virt,
while ( left )
{
unsigned int order, level;
+ unsigned int nr_contig;
+ unsigned int new_flags;
level = xen_pt_mapping_level(vfn, mfn, left, flags);
order = XEN_PT_LEVEL_ORDER(level);
ASSERT(left >= BIT(order, UL));
- rc = xen_pt_update_entry(root, pfn_to_paddr(vfn), mfn, level, flags);
- if ( rc )
- break;
+ /*
+ * Check if we can set the contiguous mapping and update the
+ * flags accordingly.
+ */
+ nr_contig = xen_pt_check_contig(vfn, mfn, level, left, flags);
+ new_flags = flags | ((nr_contig > 1) ? _PAGE_CONTIG : 0);
Here is an optional idea to make the code simpler. We could move the
flags changes (adding/removing _PAGE_CONTIG) to xen_pt_check_contig.
That way, we could remove the inner loop.
xen_pt_check_contig could check if _PAGE_CONTIG is already set and based
on alignment, it should be able to figure out when it needs to be
disabled.
My initial attempt was to do everything in a loop. But this didn't pan
out as I wanted (I felt the code was complex) and there are extra work
to be done for the next 31 entries (assuming 4KB granularity).
Hence the two loops. Unfortunately, I didn't keep my first attempt. So I
can't realy show what I wrote.
Cheers,
--
Julien Grall
