[Xen-devel] [PATCH] x86/shadow: fold p2m page accounting into sh_min_allocation()

* [Xen-devel] [PATCH] x86/shadow: fold p2m page accounting into sh_min_allocation()
@ 2019-09-05  8:34 Jan Beulich
  2019-09-06 11:27 ` Roger Pau Monné
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Jan Beulich @ 2019-09-05  8:34 UTC (permalink / raw)
  To: xen-devel
  Cc: George Dunlap, Andrew Cooper, Tim Deegan, Wei Liu, Roger Pau Monné

This is to make the function live up to the promise its name makes. And
it simplifies all callers.

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -1256,29 +1256,26 @@ static unsigned int sh_min_allocation(co
      * up of slot zero and an LAPIC page), plus one for HVM's 1-to-1 pagetable.
      */
     return shadow_min_acceptable_pages(d) +
-           max(d->tot_pages / 256,
-               is_hvm_domain(d) ? CONFIG_PAGING_LEVELS + 2 : 0U) +
-           is_hvm_domain(d);
+           max(max(d->tot_pages / 256,
+                   is_hvm_domain(d) ? CONFIG_PAGING_LEVELS + 2 : 0U) +
+               is_hvm_domain(d),
+               d->arch.paging.shadow.p2m_pages);
 }
 
 int shadow_set_allocation(struct domain *d, unsigned int pages, bool *preempted)
 {
     struct page_info *sp;
-    unsigned int lower_bound;
 
     ASSERT(paging_locked_by_me(d));
 
     if ( pages > 0 )
     {
         /* Check for minimum value. */
-        if ( pages < d->arch.paging.shadow.p2m_pages )
-            pages = 0;
-        else
-            pages -= d->arch.paging.shadow.p2m_pages;
+        unsigned int lower_bound = sh_min_allocation(d);
 
-        lower_bound = sh_min_allocation(d);
         if ( pages < lower_bound )
             pages = lower_bound;
+        pages -= d->arch.paging.shadow.p2m_pages;
     }
 
     SHADOW_PRINTK("current %i target %i\n",
@@ -2607,7 +2604,7 @@ int shadow_enable(struct domain *d, u32
 
     /* Init the shadow memory allocation if the user hasn't done so */
     old_pages = d->arch.paging.shadow.total_pages;
-    if ( old_pages < sh_min_allocation(d) + d->arch.paging.shadow.p2m_pages )
+    if ( old_pages < sh_min_allocation(d) )
     {
         paging_lock(d);
         rv = shadow_set_allocation(d, 1024, NULL); /* Use at least 4MB */
@@ -2864,8 +2861,7 @@ static int shadow_one_bit_enable(struct
 
     mode |= PG_SH_enable;
 
-    if ( d->arch.paging.shadow.total_pages <
-         sh_min_allocation(d) + d->arch.paging.shadow.p2m_pages )
+    if ( d->arch.paging.shadow.total_pages < sh_min_allocation(d) )
     {
         /* Init the shadow memory allocation if the user hasn't done so */
         if ( shadow_set_allocation(d, 1, NULL) != 0 )

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