[v8,07/15] x86_64/mm: switch to new APIs in paging_init

Commit Message

Hongyan Xia July 27, 2020, 2:21 p.m. UTC

From: Wei Liu <[e-mail]>

Map and unmap pages instead of relying on the direct map.

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

---
Changed in v8:
- replace l3/2_ro_mpt_mfn with just mfn since their lifetimes do not
  overlap

Changed in v7:
- use the new alloc_map_clear_xen_pt() helper.
- move the unmap of pl3t up a bit.
- remove the unmaps in the nomem path.
---
 xen/arch/x86/x86_64/mm.c | 35 +++++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 14 deletions(-)

Comments

Jan Beulich Aug. 7, 2020, 2:09 p.m. UTC | #1

On 27.07.2020 16:21, Hongyan Xia wrote:
> From: Wei Liu <[e-mail]>
> 
> Map and unmap pages instead of relying on the direct map.
> 
> Signed-off-by: Wei Liu <[e-mail]>
> Signed-off-by: Hongyan Xia <[e-mail]>
> Reviewed-by: Jan Beulich <[e-mail]>
> 
> ---
> Changed in v8:
> - replace l3/2_ro_mpt_mfn with just mfn since their lifetimes do not
>   overlap

Good, but ...

> --- a/xen/arch/x86/x86_64/mm.c
> +++ b/xen/arch/x86/x86_64/mm.c
> @@ -481,6 +481,7 @@ void __init paging_init(void)
>      l3_pgentry_t *l3_ro_mpt;
>      l2_pgentry_t *pl2e = NULL, *l2_ro_mpt = NULL;
>      struct page_info *l1_pg;
> +    mfn_t mfn;
>  
>      /*
>       * We setup the L3s for 1:1 mapping if host support memory hotplug
> @@ -493,22 +494,23 @@ void __init paging_init(void)
>          if ( !(l4e_get_flags(idle_pg_table[l4_table_offset(va)]) &
>                _PAGE_PRESENT) )
>          {
> -            l3_pgentry_t *pl3t = alloc_xen_pagetable();
> +            mfn_t l3mfn;

... what about this one? It's again only used ...

> +            l3_pgentry_t *pl3t = alloc_map_clear_xen_pt(&l3mfn);
>  
>              if ( !pl3t )
>                  goto nomem;
> -            clear_page(pl3t);
> +            UNMAP_DOMAIN_PAGE(pl3t);
>              l4e_write(&idle_pg_table[l4_table_offset(va)],
> -                      l4e_from_paddr(__pa(pl3t), __PAGE_HYPERVISOR_RW));
> +                      l4e_from_mfn(l3mfn, __PAGE_HYPERVISOR_RW));
>          }
>      }
>  
>      /* Create user-accessible L2 directory to map the MPT for guests. */
> -    if ( (l3_ro_mpt = alloc_xen_pagetable()) == NULL )
> +    l3_ro_mpt = alloc_map_clear_xen_pt(&mfn);

... without colliding with this first use of mfn.

Jan

Patch

diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 243014a119..ebf21d505b 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -481,6 +481,7 @@  void __init paging_init(void)
     l3_pgentry_t *l3_ro_mpt;
     l2_pgentry_t *pl2e = NULL, *l2_ro_mpt = NULL;
     struct page_info *l1_pg;
+    mfn_t mfn;
 
     /*
      * We setup the L3s for 1:1 mapping if host support memory hotplug
@@ -493,22 +494,23 @@  void __init paging_init(void)
         if ( !(l4e_get_flags(idle_pg_table[l4_table_offset(va)]) &
               _PAGE_PRESENT) )
         {
-            l3_pgentry_t *pl3t = alloc_xen_pagetable();
+            mfn_t l3mfn;
+            l3_pgentry_t *pl3t = alloc_map_clear_xen_pt(&l3mfn);
 
             if ( !pl3t )
                 goto nomem;
-            clear_page(pl3t);
+            UNMAP_DOMAIN_PAGE(pl3t);
             l4e_write(&idle_pg_table[l4_table_offset(va)],
-                      l4e_from_paddr(__pa(pl3t), __PAGE_HYPERVISOR_RW));
+                      l4e_from_mfn(l3mfn, __PAGE_HYPERVISOR_RW));
         }
     }
 
     /* Create user-accessible L2 directory to map the MPT for guests. */
-    if ( (l3_ro_mpt = alloc_xen_pagetable()) == NULL )
+    l3_ro_mpt = alloc_map_clear_xen_pt(&mfn);
+    if ( !l3_ro_mpt )
         goto nomem;
-    clear_page(l3_ro_mpt);
     l4e_write(&idle_pg_table[l4_table_offset(RO_MPT_VIRT_START)],
-              l4e_from_paddr(__pa(l3_ro_mpt), __PAGE_HYPERVISOR_RO | _PAGE_USER));
+              l4e_from_mfn(mfn, __PAGE_HYPERVISOR_RO | _PAGE_USER));
 
     /*
      * Allocate and map the machine-to-phys table.
@@ -591,12 +593,14 @@  void __init paging_init(void)
         }
         if ( !((unsigned long)pl2e & ~PAGE_MASK) )
         {
-            if ( (l2_ro_mpt = alloc_xen_pagetable()) == NULL )
+            UNMAP_DOMAIN_PAGE(l2_ro_mpt);
+
+            l2_ro_mpt = alloc_map_clear_xen_pt(&mfn);
+            if ( !l2_ro_mpt )
                 goto nomem;
-            clear_page(l2_ro_mpt);
+
             l3e_write(&l3_ro_mpt[l3_table_offset(va)],
-                      l3e_from_paddr(__pa(l2_ro_mpt),
-                                     __PAGE_HYPERVISOR_RO | _PAGE_USER));
+                      l3e_from_mfn(mfn, __PAGE_HYPERVISOR_RO | _PAGE_USER));
             pl2e = l2_ro_mpt;
             ASSERT(!l2_table_offset(va));
         }
@@ -608,13 +612,16 @@  void __init paging_init(void)
     }
 #undef CNT
 #undef MFN
+    UNMAP_DOMAIN_PAGE(l2_ro_mpt);
+    UNMAP_DOMAIN_PAGE(l3_ro_mpt);
 
     /* Create user-accessible L2 directory to map the MPT for compat guests. */
-    if ( (l2_ro_mpt = alloc_xen_pagetable()) == NULL )
+    mfn = alloc_xen_pagetable_new();
+    if ( mfn_eq(mfn, INVALID_MFN) )
         goto nomem;
-    compat_idle_pg_table_l2 = l2_ro_mpt;
-    clear_page(l2_ro_mpt);
-    pl2e = l2_ro_mpt;
+    compat_idle_pg_table_l2 = map_domain_page_global(mfn);
+    clear_page(compat_idle_pg_table_l2);
+    pl2e = compat_idle_pg_table_l2;
     /* Allocate and map the compatibility mode machine-to-phys table. */
     mpt_size = (mpt_size >> 1) + (1UL << (L2_PAGETABLE_SHIFT - 1));
     if ( mpt_size > RDWR_COMPAT_MPT_VIRT_END - RDWR_COMPAT_MPT_VIRT_START )