[PATCH 07/15] x86/PVH: lift E820 alignment requirement

[Jan Beulich <jbeulich@xxxxxxxx>]

Before reordering things (to move in particular pvh_steal_ram()
invocations ahead of the pvh_populate_p2m() one) drop an undue (and as it
turns out unnecessary) assumption: find_memory() doesn't really depend on
E820 regions to end on page boundaries.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Really the assumption towards the start of regions doesn't look to be
relevant either, yet I thought I'd limit the change to the minimum needed.
(In fact the statement immediately ahead of the assertion arranges for
page alignment, so the check is dubious altogether.)

We also could consider whether kernel_end really needs rounding up to a
page boundary: Technically there's no need, but the question is whether it
would be a good idea to have the tail of the kernel region share a page
with metadata (or, as things still are at this point of the series, the
initrd).

--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -365,6 +365,9 @@ static __init void pvh_setup_e820(struct
          * that's the minimum granularity of the 2nd stage translation. Since
          * the p2m code uses PAGE_ORDER_4K internally, also use it here in
          * order to prevent this code from getting out of sync.
+         *
+         * Note that this is only for pvh_populate_p2m().  Subsequent uses of
+         * pvh_steal_ram() will break the length part.
          */
         start = ROUNDUP(entry->addr, PAGE_SIZE << PAGE_ORDER_4K);
         end = (entry->addr + entry->size) &
@@ -506,8 +509,8 @@ static paddr_t __init find_memory(
     unsigned int i;
 
     /*
-     * The memory map is sorted and all RAM regions starts and sizes are
-     * aligned to page boundaries.
+     * The memory map is sorted and all RAM region starts are aligned to
+     * page boundaries.
      */
     for ( i = 0; i < d->arch.nr_e820; i++ )
     {
@@ -519,7 +522,7 @@ static paddr_t __init find_memory(
 
         start = MAX(ROUNDUP(d->arch.e820[i].addr, PAGE_SIZE), MB(1));
 
-        ASSERT(IS_ALIGNED(start, PAGE_SIZE) && IS_ALIGNED(end, PAGE_SIZE));
+        ASSERT(IS_ALIGNED(start, PAGE_SIZE));
 
         /*
          * NB: Even better would be to use rangesets to determine a suitable