[PATCH 04/22] x86/mm: ensure L4 idle_pg_table is not modified past boot

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

The idle_pg_table L4 is cloned to create all the other L4 Xen uses, and hence
it shouldn't be modified once further L4 are created.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/mm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 6ffacab341ad..01380fd82c9d 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5023,6 +5023,12 @@ static l3_pgentry_t *virt_to_xen_l3e(unsigned long v)
         mfn_t l3mfn;
         l3_pgentry_t *l3t = alloc_mapped_pagetable(&l3mfn);
 
+        /*
+         * dom0 is build at smp_boot, at which point we already create new L4s
+         * based on idle_pg_table.
+         */
+        BUG_ON(system_state >= SYS_STATE_smp_boot);
+
         if ( !l3t )
             return NULL;
         UNMAP_DOMAIN_PAGE(l3t);
-- 
2.45.2