[v2,4/5] x86_64/mm: map and unmap page tables in destroy_compat_m2p_mapping

Commit Message

Hongyan Xia April 8, 2020, 1:36 p.m. UTC

From: Wei Liu <[e-mail]>

Signed-off-by: Wei Liu <[e-mail]>
Signed-off-by: Hongyan Xia <[e-mail]>

---
Changed in v2:
- there is pretty much no point in keeping l3_ro_mpt mapped, just fetch
  the l3e instead, which also cleans up the code.
---
 xen/arch/x86/x86_64/mm.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

Comments

Jan Beulich April 15, 2020, 8:25 a.m. UTC | #1

On 08.04.2020 15:36, Hongyan Xia wrote:
> From: Wei Liu <[e-mail]>
> 
> Signed-off-by: Wei Liu <[e-mail]>
> Signed-off-by: Hongyan Xia <[e-mail]>
> 
> ---
> Changed in v2:
> - there is pretty much no point in keeping l3_ro_mpt mapped, just fetch
>   the l3e instead, which also cleans up the code.

Even better, there's no need to do any mapping her at all. I've
posted a pair of patches, the first of which can be seen as a
suggested replacement for the one here.

Jan

Patch

diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index d23c7e4f5b..ae8f4dd0b9 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -220,7 +220,7 @@  static void destroy_compat_m2p_mapping(struct mem_hotadd_info *info)
     unsigned long i, va, rwva, pt_pfn;
     unsigned long smap = info->spfn, emap = info->spfn;
 
-    l3_pgentry_t *l3_ro_mpt;
+    l3_pgentry_t l3e_ro_mpt;
     l2_pgentry_t *l2_ro_mpt;
 
     if ( smap > ((RDWR_COMPAT_MPT_VIRT_END - RDWR_COMPAT_MPT_VIRT_START) >> 2) )
@@ -229,11 +229,13 @@  static void destroy_compat_m2p_mapping(struct mem_hotadd_info *info)
     if ( emap > ((RDWR_COMPAT_MPT_VIRT_END - RDWR_COMPAT_MPT_VIRT_START) >> 2) )
         emap = (RDWR_COMPAT_MPT_VIRT_END - RDWR_COMPAT_MPT_VIRT_START) >> 2;
 
-    l3_ro_mpt = l4e_to_l3e(idle_pg_table[l4_table_offset(HIRO_COMPAT_MPT_VIRT_START)]);
+    l3e_ro_mpt = l3e_from_l4e(idle_pg_table[
+                                  l4_table_offset(HIRO_COMPAT_MPT_VIRT_START)],
+                              l3_table_offset(HIRO_COMPAT_MPT_VIRT_START));
 
-    ASSERT(l3e_get_flags(l3_ro_mpt[l3_table_offset(HIRO_COMPAT_MPT_VIRT_START)]) & _PAGE_PRESENT);
+    ASSERT(l3e_get_flags(l3e_ro_mpt) & _PAGE_PRESENT);
 
-    l2_ro_mpt = l3e_to_l2e(l3_ro_mpt[l3_table_offset(HIRO_COMPAT_MPT_VIRT_START)]);
+    l2_ro_mpt = map_l2t_from_l3e(l3e_ro_mpt);
 
     for ( i = smap; i < emap; )
     {
@@ -255,6 +257,8 @@  static void destroy_compat_m2p_mapping(struct mem_hotadd_info *info)
         i += 1UL << (L2_PAGETABLE_SHIFT - 2);
     }
 
+    UNMAP_DOMAIN_PAGE(l2_ro_mpt);
+
     return;
 }