diff mbox series

[v2,1/3] x86/PoD: simplify / improve p2m_pod_cache_add()

Message ID 0c61e460-122c-6486-00b7-22a9a24ee1fc@suse.com (mailing list archive)
State New, archived
Headers show
Series x86/mm: address observations made while working on XSA-388 | expand

Commit Message

Jan Beulich Jan. 4, 2022, 9:48 a.m. UTC 
Avoid recurring MFN -> page or page -> MFN translations. Drop the pretty
pointless local variable "p". Make sure the MFN logged in a debugging
error message is actually the offending one. Return negative errno
values rather than -1 (presently no caller really cares, but imo this
should change). Adjust style.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v2: Return -errno. Drop exclamation mark from log message.

Comments

Jan Beulich Jan. 27, 2022, 3:04 p.m. UTC | #1 
On 04.01.2022 10:48, Jan Beulich wrote:
> Avoid recurring MFN -> page or page -> MFN translations. Drop the pretty
> pointless local variable "p". Make sure the MFN logged in a debugging
> error message is actually the offending one. Return negative errno
> values rather than -1 (presently no caller really cares, but imo this
> should change). Adjust style.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> ---
> v2: Return -errno. Drop exclamation mark from log message.

Ping?

> --- a/xen/arch/x86/mm/p2m-pod.c
> +++ b/xen/arch/x86/mm/p2m-pod.c
> @@ -58,34 +58,27 @@ p2m_pod_cache_add(struct p2m_domain *p2m
>                    unsigned int order)
>  {
>      unsigned long i;
> -    struct page_info *p;
>      struct domain *d = p2m->domain;
> +    mfn_t mfn = page_to_mfn(page);
>  
>  #ifndef NDEBUG
> -    mfn_t mfn;
> -
> -    mfn = page_to_mfn(page);
> -
>      /* Check to make sure this is a contiguous region */
>      if ( mfn_x(mfn) & ((1UL << order) - 1) )
>      {
>          printk("%s: mfn %lx not aligned order %u! (mask %lx)\n",
>                 __func__, mfn_x(mfn), order, ((1UL << order) - 1));
> -        return -1;
> +        return -EINVAL;
>      }
>  
> -    for ( i = 0; i < 1UL << order ; i++)
> +    for ( i = 0; i < (1UL << order); i++)
>      {
> -        struct domain * od;
> +        const struct domain *od = page_get_owner(page + i);
>  
> -        p = mfn_to_page(mfn_add(mfn, i));
> -        od = page_get_owner(p);
>          if ( od != d )
>          {
> -            printk("%s: mfn %lx expected owner d%d, got owner d%d!\n",
> -                   __func__, mfn_x(mfn), d->domain_id,
> -                   od ? od->domain_id : -1);
> -            return -1;
> +            printk("%s: mfn %lx owner: expected %pd, got %pd\n",
> +                   __func__, mfn_x(mfn) + i, d, od);
> +            return -EACCES;
>          }
>      }
>  #endif
> @@ -98,16 +91,12 @@ p2m_pod_cache_add(struct p2m_domain *p2m
>       * promise to provide zero pages. So we scrub pages before using.
>       */
>      for ( i = 0; i < (1UL << order); i++ )
> -        clear_domain_page(mfn_add(page_to_mfn(page), i));
> +        clear_domain_page(mfn_add(mfn, i));
>  
>      /* First, take all pages off the domain list */
>      lock_page_alloc(p2m);
> -    for ( i = 0; i < 1UL << order ; i++ )
> -    {
> -        p = page + i;
> -        page_list_del(p, &d->page_list);
> -    }
> -
> +    for ( i = 0; i < (1UL << order); i++ )
> +        page_list_del(page + i, &d->page_list);
>      unlock_page_alloc(p2m);
>  
>      /* Then add to the appropriate populate-on-demand list. */
> 
>
Jan Beulich Feb. 24, 2022, 1:02 p.m. UTC | #2 
On 27.01.2022 16:04, Jan Beulich wrote:
> On 04.01.2022 10:48, Jan Beulich wrote:
>> Avoid recurring MFN -> page or page -> MFN translations. Drop the pretty
>> pointless local variable "p". Make sure the MFN logged in a debugging
>> error message is actually the offending one. Return negative errno
>> values rather than -1 (presently no caller really cares, but imo this
>> should change). Adjust style.
>>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>> ---
>> v2: Return -errno. Drop exclamation mark from log message.
> 
> Ping?

Another 4 weeks have passed ...

Thanks for feedback either way, Jan

>> --- a/xen/arch/x86/mm/p2m-pod.c
>> +++ b/xen/arch/x86/mm/p2m-pod.c
>> @@ -58,34 +58,27 @@ p2m_pod_cache_add(struct p2m_domain *p2m
>>                    unsigned int order)
>>  {
>>      unsigned long i;
>> -    struct page_info *p;
>>      struct domain *d = p2m->domain;
>> +    mfn_t mfn = page_to_mfn(page);
>>  
>>  #ifndef NDEBUG
>> -    mfn_t mfn;
>> -
>> -    mfn = page_to_mfn(page);
>> -
>>      /* Check to make sure this is a contiguous region */
>>      if ( mfn_x(mfn) & ((1UL << order) - 1) )
>>      {
>>          printk("%s: mfn %lx not aligned order %u! (mask %lx)\n",
>>                 __func__, mfn_x(mfn), order, ((1UL << order) - 1));
>> -        return -1;
>> +        return -EINVAL;
>>      }
>>  
>> -    for ( i = 0; i < 1UL << order ; i++)
>> +    for ( i = 0; i < (1UL << order); i++)
>>      {
>> -        struct domain * od;
>> +        const struct domain *od = page_get_owner(page + i);
>>  
>> -        p = mfn_to_page(mfn_add(mfn, i));
>> -        od = page_get_owner(p);
>>          if ( od != d )
>>          {
>> -            printk("%s: mfn %lx expected owner d%d, got owner d%d!\n",
>> -                   __func__, mfn_x(mfn), d->domain_id,
>> -                   od ? od->domain_id : -1);
>> -            return -1;
>> +            printk("%s: mfn %lx owner: expected %pd, got %pd\n",
>> +                   __func__, mfn_x(mfn) + i, d, od);
>> +            return -EACCES;
>>          }
>>      }
>>  #endif
>> @@ -98,16 +91,12 @@ p2m_pod_cache_add(struct p2m_domain *p2m
>>       * promise to provide zero pages. So we scrub pages before using.
>>       */
>>      for ( i = 0; i < (1UL << order); i++ )
>> -        clear_domain_page(mfn_add(page_to_mfn(page), i));
>> +        clear_domain_page(mfn_add(mfn, i));
>>  
>>      /* First, take all pages off the domain list */
>>      lock_page_alloc(p2m);
>> -    for ( i = 0; i < 1UL << order ; i++ )
>> -    {
>> -        p = page + i;
>> -        page_list_del(p, &d->page_list);
>> -    }
>> -
>> +    for ( i = 0; i < (1UL << order); i++ )
>> +        page_list_del(page + i, &d->page_list);
>>      unlock_page_alloc(p2m);
>>  
>>      /* Then add to the appropriate populate-on-demand list. */
>>
>>
>
George Dunlap Feb. 1, 2024, 1:48 p.m. UTC | #3 
On Tue, Jan 4, 2022 at 9:48 AM Jan Beulich <jbeulich@suse.com> wrote:

> Avoid recurring MFN -> page or page -> MFN translations. Drop the pretty
> pointless local variable "p". Make sure the MFN logged in a debugging
> error message is actually the offending one. Return negative errno
> values rather than -1 (presently no caller really cares, but imo this
> should change). Adjust style.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>

Sorry, not sure how I managed to miss this:

Reviewed-by: George Dunlap <george.dunlap@cloud.com>
diff mbox series

Patch

--- a/xen/arch/x86/mm/p2m-pod.c
+++ b/xen/arch/x86/mm/p2m-pod.c
@@ -58,34 +58,27 @@  p2m_pod_cache_add(struct p2m_domain *p2m
                   unsigned int order)
 {
     unsigned long i;
-    struct page_info *p;
     struct domain *d = p2m->domain;
+    mfn_t mfn = page_to_mfn(page);
 
 #ifndef NDEBUG
-    mfn_t mfn;
-
-    mfn = page_to_mfn(page);
-
     /* Check to make sure this is a contiguous region */
     if ( mfn_x(mfn) & ((1UL << order) - 1) )
     {
         printk("%s: mfn %lx not aligned order %u! (mask %lx)\n",
                __func__, mfn_x(mfn), order, ((1UL << order) - 1));
-        return -1;
+        return -EINVAL;
     }
 
-    for ( i = 0; i < 1UL << order ; i++)
+    for ( i = 0; i < (1UL << order); i++)
     {
-        struct domain * od;
+        const struct domain *od = page_get_owner(page + i);
 
-        p = mfn_to_page(mfn_add(mfn, i));
-        od = page_get_owner(p);
         if ( od != d )
         {
-            printk("%s: mfn %lx expected owner d%d, got owner d%d!\n",
-                   __func__, mfn_x(mfn), d->domain_id,
-                   od ? od->domain_id : -1);
-            return -1;
+            printk("%s: mfn %lx owner: expected %pd, got %pd\n",
+                   __func__, mfn_x(mfn) + i, d, od);
+            return -EACCES;
         }
     }
 #endif
@@ -98,16 +91,12 @@  p2m_pod_cache_add(struct p2m_domain *p2m
      * promise to provide zero pages. So we scrub pages before using.
      */
     for ( i = 0; i < (1UL << order); i++ )
-        clear_domain_page(mfn_add(page_to_mfn(page), i));
+        clear_domain_page(mfn_add(mfn, i));
 
     /* First, take all pages off the domain list */
     lock_page_alloc(p2m);
-    for ( i = 0; i < 1UL << order ; i++ )
-    {
-        p = page + i;
-        page_list_del(p, &d->page_list);
-    }
-
+    for ( i = 0; i < (1UL << order); i++ )
+        page_list_del(page + i, &d->page_list);
     unlock_page_alloc(p2m);
 
     /* Then add to the appropriate populate-on-demand list. */