[Xen-devel] [PATCH RFC 01/12] x86/np2m: refactor p2m_get_nestedp2m()

[Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>]

1. Add a helper function assign_np2m()
2. Remove useless volatile
3. Update function's comment in the header
4. Minor style fixes ('\n' and d)

Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
---
 xen/arch/x86/mm/p2m.c     | 31 ++++++++++++++++++-------------
 xen/include/asm-x86/p2m.h |  6 +++---
 2 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index e8a57d118c..b8c8bba421 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1773,14 +1773,24 @@ p2m_flush_nestedp2m(struct domain *d)
         p2m_flush_table(d->arch.nested_p2m[i]);
 }
 
+static void assign_np2m(struct vcpu *v, struct p2m_domain *p2m)
+{
+    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
+    struct domain *d = v->domain;
+
+    /* Bring this np2m to the top of the LRU list */
+    p2m_getlru_nestedp2m(d, p2m);
+
+    nv->nv_flushp2m = 0;
+    nv->nv_p2m = p2m;
+    cpumask_set_cpu(v->processor, p2m->dirty_cpumask);
+}
+
 struct p2m_domain *
 p2m_get_nestedp2m(struct vcpu *v, uint64_t np2m_base)
 {
-    /* Use volatile to prevent gcc to cache nv->nv_p2m in a cpu register as
-     * this may change within the loop by an other (v)cpu.
-     */
-    volatile struct nestedvcpu *nv = &vcpu_nestedhvm(v);
-    struct domain *d;
+    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
+    struct domain *d = v->domain;
     struct p2m_domain *p2m;
 
     /* Mask out low bits; this avoids collisions with P2M_BASE_EADDR */
@@ -1790,7 +1800,6 @@ p2m_get_nestedp2m(struct vcpu *v, uint64_t np2m_base)
         nv->nv_p2m = NULL;
     }
 
-    d = v->domain;
     nestedp2m_lock(d);
     p2m = nv->nv_p2m;
     if ( p2m ) 
@@ -1798,15 +1807,13 @@ p2m_get_nestedp2m(struct vcpu *v, uint64_t np2m_base)
         p2m_lock(p2m);
         if ( p2m->np2m_base == np2m_base || p2m->np2m_base == P2M_BASE_EADDR )
         {
-            nv->nv_flushp2m = 0;
-            p2m_getlru_nestedp2m(d, p2m);
-            nv->nv_p2m = p2m;
             if ( p2m->np2m_base == P2M_BASE_EADDR )
                 hvm_asid_flush_vcpu(v);
             p2m->np2m_base = np2m_base;
-            cpumask_set_cpu(v->processor, p2m->dirty_cpumask);
+            assign_np2m(v, p2m);
             p2m_unlock(p2m);
             nestedp2m_unlock(d);
+
             return p2m;
         }
         p2m_unlock(p2m);
@@ -1817,11 +1824,9 @@ p2m_get_nestedp2m(struct vcpu *v, uint64_t np2m_base)
     p2m = p2m_getlru_nestedp2m(d, NULL);
     p2m_flush_table(p2m);
     p2m_lock(p2m);
-    nv->nv_p2m = p2m;
     p2m->np2m_base = np2m_base;
-    nv->nv_flushp2m = 0;
     hvm_asid_flush_vcpu(v);
-    cpumask_set_cpu(v->processor, p2m->dirty_cpumask);
+    assign_np2m(v, p2m);
     p2m_unlock(p2m);
     nestedp2m_unlock(d);
 
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 6395e8fd1d..9086bb35dc 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -359,9 +359,9 @@ struct p2m_domain {
 /* get host p2m table */
 #define p2m_get_hostp2m(d)      ((d)->arch.p2m)
 
-/* Get p2m table (re)usable for specified np2m base.
- * Automatically destroys and re-initializes a p2m if none found.
- * If np2m_base == 0 then v->arch.hvm_vcpu.guest_cr[3] is used.
+/*
+ * Assigns an np2m with the specified np2m_base to the specified vCPU
+ * and returns that np2m.
  */
 struct p2m_domain *p2m_get_nestedp2m(struct vcpu *v, uint64_t np2m_base);
 
-- 
2.11.0


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