diff mbox series

[v4,3/9] x86/mm: introduce l{1, 2}t local variables to map_pages_to_xen

Message ID 032b7288fc1606a68dc18cf5709c83540717f38a.1575477921.git.hongyxia@amazon.com (mailing list archive)
State New, archived
Headers show
Series Add alternative API for Xen PTEs | expand

Commit Message

Xia, Hongyan Dec. 4, 2019, 5:10 p.m. UTC 
From: Wei Liu <wei.liu2@citrix.com>

The pl2e and pl1e variables are heavily (ab)used in that function. It
is fine at the moment because all page tables are always mapped so
there is no need to track the life time of each variable.

We will soon have the requirement to map and unmap page tables. We
need to track the life time of each variable to avoid leakage.

Introduce some l{1,2}t variables with limited scope so that we can
track life time of pointers to xen page tables more easily.

No functional change.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
 xen/arch/x86/mm.c | 75 ++++++++++++++++++++++++++---------------------
 1 file changed, 42 insertions(+), 33 deletions(-)

Comments

Xia, Hongyan Dec. 4, 2019, 6:01 p.m. UTC | #1 
>> @@ -5272,6 +5279,7 @@ int map_pages_to_xen(
>>                      ((1u << PAGETABLE_ORDER) - 1)) == 0)) )
>>              {
>>                  unsigned long base_mfn;
>> +                l1_pgentry_t *l1t;
>
> const, as this looks to be used for lookup only?

I cannot do this for now since variables like l1t are still using the
old API which is non-const. I can change it once they are switched to
the new const API in later patches.

Hongyan
Jan Beulich Dec. 5, 2019, 8:38 a.m. UTC | #2 
On 04.12.2019 19:01, Xia, Hongyan wrote:
>>> @@ -5272,6 +5279,7 @@ int map_pages_to_xen(
>>>                      ((1u << PAGETABLE_ORDER) - 1)) == 0)) )
>>>              {
>>>                  unsigned long base_mfn;
>>> +                l1_pgentry_t *l1t;
>>
>> const, as this looks to be used for lookup only?
> 
> I cannot do this for now since variables like l1t are still using the
> old API which is non-const. I can change it once they are switched to
> the new const API in later patches.

Maybe I've indeed picked an example where this won't work yet,
but there look to be cases where the old interface wouldn't
get in the way. I'd appreciate if at least those cases could
have const added right away.

Jan
diff mbox series

Patch

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index ca362ad638..790578d2b3 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5234,10 +5234,12 @@  int map_pages_to_xen(
                 }
                 else
                 {
-                    pl2e = l3e_to_l2e(ol3e);
+                    l2_pgentry_t *l2t;
+
+                    l2t = l3e_to_l2e(ol3e);
                     for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
                     {
-                        ol2e = pl2e[i];
+                        ol2e = l2t[i];
                         if ( !(l2e_get_flags(ol2e) & _PAGE_PRESENT) )
                             continue;
                         if ( l2e_get_flags(ol2e) & _PAGE_PSE )
@@ -5245,21 +5247,22 @@  int map_pages_to_xen(
                         else
                         {
                             unsigned int j;
+                            l1_pgentry_t *l1t;
 
-                            pl1e = l2e_to_l1e(ol2e);
+                            l1t = l2e_to_l1e(ol2e);
                             for ( j = 0; j < L1_PAGETABLE_ENTRIES; j++ )
-                                flush_flags(l1e_get_flags(pl1e[j]));
+                                flush_flags(l1e_get_flags(l1t[j]));
                         }
                     }
                     flush_area(virt, flush_flags);
                     for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
                     {
-                        ol2e = pl2e[i];
+                        ol2e = l2t[i];
                         if ( (l2e_get_flags(ol2e) & _PAGE_PRESENT) &&
                              !(l2e_get_flags(ol2e) & _PAGE_PSE) )
                             free_xen_pagetable(l2e_to_l1e(ol2e));
                     }
-                    free_xen_pagetable(pl2e);
+                    free_xen_pagetable(l2t);
                 }
             }
 
@@ -5275,6 +5278,7 @@  int map_pages_to_xen(
         {
             unsigned int flush_flags =
                 FLUSH_TLB | FLUSH_ORDER(2 * PAGETABLE_ORDER);
+            l2_pgentry_t *l2t;
 
             /* Skip this PTE if there is no change. */
             if ( ((l3e_get_pfn(ol3e) & ~(L2_PAGETABLE_ENTRIES *
@@ -5296,12 +5300,12 @@  int map_pages_to_xen(
                 continue;
             }
 
-            pl2e = alloc_xen_pagetable();
-            if ( pl2e == NULL )
+            l2t = alloc_xen_pagetable();
+            if ( l2t == NULL )
                 return -ENOMEM;
 
             for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
-                l2e_write(pl2e + i,
+                l2e_write(l2t + i,
                           l2e_from_pfn(l3e_get_pfn(ol3e) +
                                        (i << PAGETABLE_ORDER),
                                        l3e_get_flags(ol3e)));
@@ -5314,15 +5318,15 @@  int map_pages_to_xen(
             if ( (l3e_get_flags(*pl3e) & _PAGE_PRESENT) &&
                  (l3e_get_flags(*pl3e) & _PAGE_PSE) )
             {
-                l3e_write_atomic(pl3e, l3e_from_mfn(virt_to_mfn(pl2e),
+                l3e_write_atomic(pl3e, l3e_from_mfn(virt_to_mfn(l2t),
                                                     __PAGE_HYPERVISOR));
-                pl2e = NULL;
+                l2t = NULL;
             }
             if ( locking )
                 spin_unlock(&map_pgdir_lock);
             flush_area(virt, flush_flags);
-            if ( pl2e )
-                free_xen_pagetable(pl2e);
+            if ( l2t )
+                free_xen_pagetable(l2t);
         }
 
         pl2e = virt_to_xen_l2e(virt);
@@ -5350,11 +5354,13 @@  int map_pages_to_xen(
                 }
                 else
                 {
-                    pl1e = l2e_to_l1e(ol2e);
+                    l1_pgentry_t *l1t;
+
+                    l1t = l2e_to_l1e(ol2e);
                     for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
-                        flush_flags(l1e_get_flags(pl1e[i]));
+                        flush_flags(l1e_get_flags(l1t[i]));
                     flush_area(virt, flush_flags);
-                    free_xen_pagetable(pl1e);
+                    free_xen_pagetable(l1t);
                 }
             }
 
@@ -5376,6 +5382,7 @@  int map_pages_to_xen(
             {
                 unsigned int flush_flags =
                     FLUSH_TLB | FLUSH_ORDER(PAGETABLE_ORDER);
+                l1_pgentry_t *l1t;
 
                 /* Skip this PTE if there is no change. */
                 if ( (((l2e_get_pfn(*pl2e) & ~(L1_PAGETABLE_ENTRIES - 1)) +
@@ -5395,12 +5402,12 @@  int map_pages_to_xen(
                     goto check_l3;
                 }
 
-                pl1e = alloc_xen_pagetable();
-                if ( pl1e == NULL )
+                l1t = alloc_xen_pagetable();
+                if ( l1t == NULL )
                     return -ENOMEM;
 
                 for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
-                    l1e_write(&pl1e[i],
+                    l1e_write(&l1t[i],
                               l1e_from_pfn(l2e_get_pfn(*pl2e) + i,
                                            lNf_to_l1f(l2e_get_flags(*pl2e))));
 
@@ -5412,15 +5419,15 @@  int map_pages_to_xen(
                 if ( (l2e_get_flags(*pl2e) & _PAGE_PRESENT) &&
                      (l2e_get_flags(*pl2e) & _PAGE_PSE) )
                 {
-                    l2e_write_atomic(pl2e, l2e_from_mfn(virt_to_mfn(pl1e),
+                    l2e_write_atomic(pl2e, l2e_from_mfn(virt_to_mfn(l1t),
                                                         __PAGE_HYPERVISOR));
-                    pl1e = NULL;
+                    l1t = NULL;
                 }
                 if ( locking )
                     spin_unlock(&map_pgdir_lock);
                 flush_area(virt, flush_flags);
-                if ( pl1e )
-                    free_xen_pagetable(pl1e);
+                if ( l1t )
+                    free_xen_pagetable(l1t);
             }
 
             pl1e  = l2e_to_l1e(*pl2e) + l1_table_offset(virt);
@@ -5445,6 +5452,7 @@  int map_pages_to_xen(
                     ((1u << PAGETABLE_ORDER) - 1)) == 0)) )
             {
                 unsigned long base_mfn;
+                l1_pgentry_t *l1t;
 
                 if ( locking )
                     spin_lock(&map_pgdir_lock);
@@ -5468,11 +5476,11 @@  int map_pages_to_xen(
                     goto check_l3;
                 }
 
-                pl1e = l2e_to_l1e(ol2e);
-                base_mfn = l1e_get_pfn(*pl1e) & ~(L1_PAGETABLE_ENTRIES - 1);
-                for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++, pl1e++ )
-                    if ( (l1e_get_pfn(*pl1e) != (base_mfn + i)) ||
-                         (l1e_get_flags(*pl1e) != flags) )
+                l1t = l2e_to_l1e(ol2e);
+                base_mfn = l1e_get_pfn(l1t[0]) & ~(L1_PAGETABLE_ENTRIES - 1);
+                for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
+                    if ( (l1e_get_pfn(l1t[i]) != (base_mfn + i)) ||
+                         (l1e_get_flags(l1t[i]) != flags) )
                         break;
                 if ( i == L1_PAGETABLE_ENTRIES )
                 {
@@ -5498,6 +5506,7 @@  int map_pages_to_xen(
                 ((1UL << (L3_PAGETABLE_SHIFT - PAGE_SHIFT)) - 1))) )
         {
             unsigned long base_mfn;
+            l2_pgentry_t *l2t;
 
             if ( locking )
                 spin_lock(&map_pgdir_lock);
@@ -5515,13 +5524,13 @@  int map_pages_to_xen(
                 continue;
             }
 
-            pl2e = l3e_to_l2e(ol3e);
-            base_mfn = l2e_get_pfn(*pl2e) & ~(L2_PAGETABLE_ENTRIES *
+            l2t = l3e_to_l2e(ol3e);
+            base_mfn = l2e_get_pfn(l2t[0]) & ~(L2_PAGETABLE_ENTRIES *
                                               L1_PAGETABLE_ENTRIES - 1);
-            for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++, pl2e++ )
-                if ( (l2e_get_pfn(*pl2e) !=
+            for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
+                if ( (l2e_get_pfn(l2t[i]) !=
                       (base_mfn + (i << PAGETABLE_ORDER))) ||
-                     (l2e_get_flags(*pl2e) != l1f_to_lNf(flags)) )
+                     (l2e_get_flags(l2t[i]) != l1f_to_lNf(flags)) )
                     break;
             if ( i == L2_PAGETABLE_ENTRIES )
             {