[1/5] x86/p2m: paging_write_p2m_entry() is a private function

Commit Message

Jan Beulich Oct. 28, 2020, 9:22 a.m. UTC

As it gets installed by p2m_pt_init(), it doesn't need to live in
paging.c. The function working in terms of l1_pgentry_t even further
indicates its non-paging-generic nature. Move it and drop its
paging_ prefix, not adding any new one now that it's static.

This then also makes more obvious that in the EPT case we wouldn't
risk mistakenly calling through the NULL hook pointer.

Signed-off-by: Jan Beulich <[e-mail]>

Comments

Roger Pau Monné Nov. 10, 2020, 10:27 a.m. UTC | #1

On Wed, Oct 28, 2020 at 10:22:04AM +0100, Jan Beulich wrote:
> As it gets installed by p2m_pt_init(), it doesn't need to live in
> paging.c. The function working in terms of l1_pgentry_t even further
> indicates its non-paging-generic nature. Move it and drop its
> paging_ prefix, not adding any new one now that it's static.
> 
> This then also makes more obvious that in the EPT case we wouldn't
> risk mistakenly calling through the NULL hook pointer.
> 
> Signed-off-by: Jan Beulich <[e-mail]>

Acked-by: Roger Pau Monné <[e-mail]>

> 
> --- a/xen/arch/x86/mm/p2m-pt.c
> +++ b/xen/arch/x86/mm/p2m-pt.c
> @@ -108,6 +108,31 @@ static unsigned long p2m_type_to_flags(c
>      }
>  }
>  
> +/*
> + * Atomically write a P2M entry and update the paging-assistance state
> + * appropriately.
> + * Arguments: the domain in question, the GFN whose mapping is being updated,
> + * a pointer to the entry to be written, the MFN in which the entry resides,
> + * the new contents of the entry, and the level in the p2m tree at which
> + * we are writing.
> + */
> +static int write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
> +                           l1_pgentry_t *p, l1_pgentry_t new,
> +                           unsigned int level)
> +{
> +    struct domain *d = p2m->domain;
> +    struct vcpu *v = current;

I think you could constify both?

Thanks, Roger.

Jan Beulich Nov. 10, 2020, 10:32 a.m. UTC | #2

On 10.11.2020 11:27, Roger Pau Monné wrote:
> On Wed, Oct 28, 2020 at 10:22:04AM +0100, Jan Beulich wrote:
>> As it gets installed by p2m_pt_init(), it doesn't need to live in
>> paging.c. The function working in terms of l1_pgentry_t even further
>> indicates its non-paging-generic nature. Move it and drop its
>> paging_ prefix, not adding any new one now that it's static.
>>
>> This then also makes more obvious that in the EPT case we wouldn't
>> risk mistakenly calling through the NULL hook pointer.
>>
>> Signed-off-by: Jan Beulich <[e-mail]>
> 
> Acked-by: Roger Pau Monné <[e-mail]>

Thanks.

>> --- a/xen/arch/x86/mm/p2m-pt.c
>> +++ b/xen/arch/x86/mm/p2m-pt.c
>> @@ -108,6 +108,31 @@ static unsigned long p2m_type_to_flags(c
>>      }
>>  }
>>  
>> +/*
>> + * Atomically write a P2M entry and update the paging-assistance state
>> + * appropriately.
>> + * Arguments: the domain in question, the GFN whose mapping is being updated,
>> + * a pointer to the entry to be written, the MFN in which the entry resides,
>> + * the new contents of the entry, and the level in the p2m tree at which
>> + * we are writing.
>> + */
>> +static int write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
>> +                           l1_pgentry_t *p, l1_pgentry_t new,
>> +                           unsigned int level)
>> +{
>> +    struct domain *d = p2m->domain;
>> +    struct vcpu *v = current;
> 
> I think you could constify both?

For v it looks like I could. For d a subsequent patch would then
need to undo it, so I'd prefer to keep it this way here.

Jan

Patch

--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -108,6 +108,31 @@  static unsigned long p2m_type_to_flags(c
     }
 }
 
+/*
+ * Atomically write a P2M entry and update the paging-assistance state
+ * appropriately.
+ * Arguments: the domain in question, the GFN whose mapping is being updated,
+ * a pointer to the entry to be written, the MFN in which the entry resides,
+ * the new contents of the entry, and the level in the p2m tree at which
+ * we are writing.
+ */
+static int write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
+                           l1_pgentry_t *p, l1_pgentry_t new,
+                           unsigned int level)
+{
+    struct domain *d = p2m->domain;
+    struct vcpu *v = current;
+    int rc = 0;
+
+    if ( v->domain != d )
+        v = d->vcpu ? d->vcpu[0] : NULL;
+    if ( likely(v && paging_mode_enabled(d) && paging_get_hostmode(v)) )
+        rc = paging_get_hostmode(v)->write_p2m_entry(p2m, gfn, p, new, level);
+    else
+        safe_write_pte(p, new);
+
+    return rc;
+}
 
 // Find the next level's P2M entry, checking for out-of-range gfn's...
 // Returns NULL on error.
@@ -594,7 +619,7 @@  p2m_pt_set_entry(struct p2m_domain *p2m,
         entry_content.l1 = l3e_content.l3;
 
         rc = p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 3);
-        /* NB: paging_write_p2m_entry() handles tlb flushes properly */
+        /* NB: write_p2m_entry() handles tlb flushes properly */
         if ( rc )
             goto out;
     }
@@ -631,7 +656,7 @@  p2m_pt_set_entry(struct p2m_domain *p2m,
 
         /* level 1 entry */
         rc = p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 1);
-        /* NB: paging_write_p2m_entry() handles tlb flushes properly */
+        /* NB: write_p2m_entry() handles tlb flushes properly */
         if ( rc )
             goto out;
     }
@@ -666,7 +691,7 @@  p2m_pt_set_entry(struct p2m_domain *p2m,
         entry_content.l1 = l2e_content.l2;
 
         rc = p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 2);
-        /* NB: paging_write_p2m_entry() handles tlb flushes properly */
+        /* NB: write_p2m_entry() handles tlb flushes properly */
         if ( rc )
             goto out;
     }
@@ -1107,7 +1132,7 @@  void p2m_pt_init(struct p2m_domain *p2m)
     p2m->recalc = do_recalc;
     p2m->change_entry_type_global = p2m_pt_change_entry_type_global;
     p2m->change_entry_type_range = p2m_pt_change_entry_type_range;
-    p2m->write_p2m_entry = paging_write_p2m_entry;
+    p2m->write_p2m_entry = write_p2m_entry;
 #if P2M_AUDIT
     p2m->audit_p2m = p2m_pt_audit_p2m;
 #else
--- a/xen/arch/x86/mm/paging.c
+++ b/xen/arch/x86/mm/paging.c
@@ -941,27 +941,7 @@  void paging_update_nestedmode(struct vcp
         v->arch.paging.nestedmode = NULL;
     hvm_asid_flush_vcpu(v);
 }
-#endif
 
-int paging_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
-                           l1_pgentry_t *p, l1_pgentry_t new,
-                           unsigned int level)
-{
-    struct domain *d = p2m->domain;
-    struct vcpu *v = current;
-    int rc = 0;
-
-    if ( v->domain != d )
-        v = d->vcpu ? d->vcpu[0] : NULL;
-    if ( likely(v && paging_mode_enabled(d) && paging_get_hostmode(v) != NULL) )
-        rc = paging_get_hostmode(v)->write_p2m_entry(p2m, gfn, p, new, level);
-    else
-        safe_write_pte(p, new);
-
-    return rc;
-}
-
-#ifdef CONFIG_HVM
 int __init paging_set_allocation(struct domain *d, unsigned int pages,
                                  bool *preempted)
 {
--- a/xen/include/asm-x86/paging.h
+++ b/xen/include/asm-x86/paging.h
@@ -371,18 +371,6 @@  static inline void safe_write_pte(l1_pge
     *p = new;
 }
 
-/* Atomically write a P2M entry and update the paging-assistance state 
- * appropriately. 
- * Arguments: the domain in question, the GFN whose mapping is being updated, 
- * a pointer to the entry to be written, the MFN in which the entry resides, 
- * the new contents of the entry, and the level in the p2m tree at which 
- * we are writing. */
-struct p2m_domain;
-
-int paging_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
-                           l1_pgentry_t *p, l1_pgentry_t new,
-                           unsigned int level);
-
 /*
  * Called from the guest to indicate that the a process is being
  * torn down and its pagetables will soon be discarded.