[Xen-devel] [PATCH v3 1/3] x86/mm: Introduce altp2m_get_gfn_type_access

[Alexandru Stefan ISAILA <aisaila@xxxxxxxxxxxxxxx>]

This patch moves common code from p2m_set_altp2m_mem_access() and
p2m_change_altp2m_gfn() into one function

Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>

---
Changes since V2:
        - Change var name from found_in_hostp2m to copied_from_hostp2m
        - Move the type check from altp2m_get_gfn_type_access() to the
        callers.
---
 xen/arch/x86/mm/mem_access.c | 32 ++++++++++++----------------
 xen/arch/x86/mm/p2m.c        | 41 ++++++++++++++----------------------
 xen/include/asm-x86/p2m.h    | 19 +++++++++++++++++
 3 files changed, 49 insertions(+), 43 deletions(-)

diff --git a/xen/arch/x86/mm/mem_access.c b/xen/arch/x86/mm/mem_access.c
index 56c06a4fc6..bf67ddb15a 100644
--- a/xen/arch/x86/mm/mem_access.c
+++ b/xen/arch/x86/mm/mem_access.c
@@ -265,31 +265,27 @@ int p2m_set_altp2m_mem_access(struct domain *d, struct 
p2m_domain *hp2m,
     unsigned int page_order;
     unsigned long gfn_l = gfn_x(gfn);
     int rc;
+    bool copied_from_hostp2m;
 
-    mfn = ap2m->get_entry(ap2m, gfn, &t, &old_a, 0, NULL, NULL);
+    mfn = altp2m_get_gfn_type_access(ap2m, gfn, &t, &old_a, &page_order, 
&copied_from_hostp2m);
 
-    /* Check host p2m if no valid entry in alternate */
     if ( !mfn_valid(mfn) )
+        return -ESRCH;
+
+    /* If this is a superpage, copy that first */
+    if ( page_order != PAGE_ORDER_4K && copied_from_hostp2m )
     {
+        unsigned long mask = ~((1UL << page_order) - 1);
+        gfn_t gfn2 = _gfn(gfn_l & mask);
+        mfn_t mfn2 = _mfn(mfn_x(mfn) & mask);
 
-        mfn = __get_gfn_type_access(hp2m, gfn_l, &t, &old_a,
-                                    P2M_ALLOC | P2M_UNSHARE, &page_order, 0);
+        /* Note: currently it is not safe to remap to a shared entry */
+        if ( t != p2m_ram_rw )
+            return -ESRCH;
 
-        rc = -ESRCH;
-        if ( !mfn_valid(mfn) || t != p2m_ram_rw )
+        rc = ap2m->set_entry(ap2m, gfn2, mfn2, page_order, t, old_a, 1);
+        if ( rc )
             return rc;
-
-        /* If this is a superpage, copy that first */
-        if ( page_order != PAGE_ORDER_4K )
-        {
-            unsigned long mask = ~((1UL << page_order) - 1);
-            gfn_t gfn2 = _gfn(gfn_l & mask);
-            mfn_t mfn2 = _mfn(mfn_x(mfn) & mask);
-
-            rc = ap2m->set_entry(ap2m, gfn2, mfn2, page_order, t, old_a, 1);
-            if ( rc )
-                return rc;
-        }
     }
 
     /*
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index b9bbb8f485..d38d7c29ca 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -2626,6 +2626,7 @@ int p2m_change_altp2m_gfn(struct domain *d, unsigned int 
idx,
     mfn_t mfn;
     unsigned int page_order;
     int rc = -EINVAL;
+    bool copied_from_hostp2m;
 
     if ( idx >= MAX_ALTP2M || d->arch.altp2m_eptp[idx] == mfn_x(INVALID_MFN) )
         return rc;
@@ -2636,7 +2637,7 @@ int p2m_change_altp2m_gfn(struct domain *d, unsigned int 
idx,
     p2m_lock(hp2m);
     p2m_lock(ap2m);
 
-    mfn = ap2m->get_entry(ap2m, old_gfn, &t, &a, 0, NULL, NULL);
+    mfn = altp2m_get_gfn_type_access(ap2m, old_gfn, &t, &a, &page_order, 
&copied_from_hostp2m);
 
     if ( gfn_eq(new_gfn, INVALID_GFN) )
     {
@@ -2646,37 +2647,27 @@ int p2m_change_altp2m_gfn(struct domain *d, unsigned 
int idx,
         goto out;
     }
 
-    /* Check host p2m if no valid entry in alternate */
-    if ( !mfn_valid(mfn) )
-    {
-        mfn = __get_gfn_type_access(hp2m, gfn_x(old_gfn), &t, &a,
-                                    P2M_ALLOC, &page_order, 0);
+    if ( !mfn_valid(mfn) || (t != p2m_ram_rw && copied_from_hostp2m) )
+         goto out;
 
-        if ( !mfn_valid(mfn) || t != p2m_ram_rw )
-            goto out;
-
-        /* If this is a superpage, copy that first */
-        if ( page_order != PAGE_ORDER_4K )
-        {
-            gfn_t gfn;
-            unsigned long mask;
+    /* If this is a superpage, copy that first */
+    if ( page_order != PAGE_ORDER_4K && copied_from_hostp2m )
+    {
+        gfn_t gfn;
+        unsigned long mask;
 
-            mask = ~((1UL << page_order) - 1);
-            gfn = _gfn(gfn_x(old_gfn) & mask);
-            mfn = _mfn(mfn_x(mfn) & mask);
+        mask = ~((1UL << page_order) - 1);
+        gfn = _gfn(gfn_x(old_gfn) & mask);
+        mfn = _mfn(mfn_x(mfn) & mask);
 
-            if ( ap2m->set_entry(ap2m, gfn, mfn, page_order, t, a, 1) )
-                goto out;
-        }
+        if ( ap2m->set_entry(ap2m, gfn, mfn, page_order, t, a, 1) )
+            goto out;
     }
 
-    mfn = ap2m->get_entry(ap2m, new_gfn, &t, &a, 0, NULL, NULL);
-
-    if ( !mfn_valid(mfn) )
-        mfn = hp2m->get_entry(hp2m, new_gfn, &t, &a, 0, NULL, NULL);
+    mfn = altp2m_get_gfn_type_access(ap2m, new_gfn, &t, &a, &page_order, 
&copied_from_hostp2m);
 
     /* Note: currently it is not safe to remap to a shared entry */
-    if ( !mfn_valid(mfn) || (t != p2m_ram_rw) )
+    if ( !mfn_valid(mfn) || (t != p2m_ram_rw && copied_from_hostp2m) )
         goto out;
 
     if ( !ap2m->set_entry(ap2m, old_gfn, mfn, PAGE_ORDER_4K, t, a,
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 2801a8ccca..6de1546d76 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -448,6 +448,25 @@ static inline mfn_t __nonnull(3) get_gfn_type(
     return get_gfn_type_access(p2m_get_hostp2m(d), gfn, t, &a, q, NULL);
 }
 
+static inline mfn_t altp2m_get_gfn_type_access(
+    struct p2m_domain *ap2m, gfn_t gfn, p2m_type_t *t, p2m_access_t *a,
+    unsigned int *page_order, bool *copied_from_hostp2m)
+{
+    mfn_t mfn = ap2m->get_entry(ap2m, gfn, t, a, 0, NULL, NULL);
+
+    *copied_from_hostp2m = false;
+
+    /* Check host p2m if no valid entry in alternate */
+    if ( !mfn_valid(mfn) )
+    {
+        mfn = __get_gfn_type_access(p2m_get_hostp2m(ap2m->domain), gfn_x(gfn), 
t, a,
+                                    P2M_ALLOC | P2M_UNSHARE, page_order, 
false);
+        *copied_from_hostp2m = mfn_valid(mfn);
+    }
+
+    return mfn;
+}
+
 /* Syntactic sugar: most callers will use one of these. */
 #define get_gfn(d, g, t)         get_gfn_type((d), (g), (t), P2M_ALLOC)
 #define get_gfn_query(d, g, t)   get_gfn_type((d), (g), (t), 0)
-- 
2.17.1

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