[v6,06/15] x86_64/mm: introduce pl2e in paging_init

Commit Message

Hongyan Xia April 24, 2020, 2:08 p.m. UTC

From: Wei Liu <[e-mail]>

Introduce pl2e so that we can use l2_ro_mpt to point to the page table
itself.

No functional change.

Signed-off-by: Wei Liu <[e-mail]>
---
 xen/arch/x86/x86_64/mm.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

Comments

Jan Beulich May 20, 2020, 9:35 a.m. UTC | #1

On 24.04.2020 16:08, Hongyan Xia wrote:
> From: Wei Liu <[e-mail]>
> 
> Introduce pl2e so that we can use l2_ro_mpt to point to the page table
> itself.
> 
> No functional change.
> 
> Signed-off-by: Wei Liu <[e-mail]>

In principle I'm fine with the change, as a preparatory one for
the next patch. The description, however, suggests this is a
change for the sake of making a change: introducing a local
variable that's not really needed for anything.

Jan

Patch

diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 6557255494..35f9de4ad4 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -479,7 +479,7 @@  void __init paging_init(void)
     unsigned long i, mpt_size, va;
     unsigned int n, memflags;
     l3_pgentry_t *l3_ro_mpt;
-    l2_pgentry_t *l2_ro_mpt = NULL;
+    l2_pgentry_t *pl2e = NULL, *l2_ro_mpt = NULL;
     struct page_info *l1_pg;
 
     /*
@@ -529,7 +529,7 @@  void __init paging_init(void)
             (L2_PAGETABLE_SHIFT - 3 + PAGE_SHIFT)));
 
         if ( cpu_has_page1gb &&
-             !((unsigned long)l2_ro_mpt & ~PAGE_MASK) &&
+             !((unsigned long)pl2e & ~PAGE_MASK) &&
              (mpt_size >> L3_PAGETABLE_SHIFT) > (i >> PAGETABLE_ORDER) )
         {
             unsigned int k, holes;
@@ -589,7 +589,7 @@  void __init paging_init(void)
             memset((void *)(RDWR_MPT_VIRT_START + (i << L2_PAGETABLE_SHIFT)),
                    0xFF, 1UL << L2_PAGETABLE_SHIFT);
         }
-        if ( !((unsigned long)l2_ro_mpt & ~PAGE_MASK) )
+        if ( !((unsigned long)pl2e & ~PAGE_MASK) )
         {
             if ( (l2_ro_mpt = alloc_xen_pagetable()) == NULL )
                 goto nomem;
@@ -597,13 +597,14 @@  void __init paging_init(void)
             l3e_write(&l3_ro_mpt[l3_table_offset(va)],
                       l3e_from_paddr(__pa(l2_ro_mpt),
                                      __PAGE_HYPERVISOR_RO | _PAGE_USER));
+            pl2e = l2_ro_mpt;
             ASSERT(!l2_table_offset(va));
         }
         /* NB. Cannot be GLOBAL: guest user mode should not see it. */
         if ( l1_pg )
-            l2e_write(l2_ro_mpt, l2e_from_page(
+            l2e_write(pl2e, l2e_from_page(
                 l1_pg, /*_PAGE_GLOBAL|*/_PAGE_PSE|_PAGE_USER|_PAGE_PRESENT));
-        l2_ro_mpt++;
+        pl2e++;
     }
 #undef CNT
 #undef MFN
@@ -613,6 +614,7 @@  void __init paging_init(void)
         goto nomem;
     compat_idle_pg_table_l2 = l2_ro_mpt;
     clear_page(l2_ro_mpt);
+    pl2e = l2_ro_mpt;
     /* 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 )
@@ -625,7 +627,7 @@  void __init paging_init(void)
              sizeof(*compat_machine_to_phys_mapping))
     BUILD_BUG_ON((sizeof(*frame_table) & ~sizeof(*frame_table)) % \
                  sizeof(*compat_machine_to_phys_mapping));
-    for ( i = 0; i < (mpt_size >> L2_PAGETABLE_SHIFT); i++, l2_ro_mpt++ )
+    for ( i = 0; i < (mpt_size >> L2_PAGETABLE_SHIFT); i++, pl2e++ )
     {
         memflags = MEMF_node(phys_to_nid(i <<
             (L2_PAGETABLE_SHIFT - 2 + PAGE_SHIFT)));
@@ -647,7 +649,7 @@  void __init paging_init(void)
                         (i << L2_PAGETABLE_SHIFT)),
                0xFF, 1UL << L2_PAGETABLE_SHIFT);
         /* NB. Cannot be GLOBAL as the ptes get copied into per-VM space. */
-        l2e_write(l2_ro_mpt, l2e_from_page(l1_pg, _PAGE_PSE|_PAGE_PRESENT));
+        l2e_write(pl2e, l2e_from_page(l1_pg, _PAGE_PSE|_PAGE_PRESENT));
     }
 #undef CNT
 #undef MFN