[Xen-devel] [PATCH 2/6] x86/mm: use optional cache in guest_walk_tables()

["Jan Beulich" <JBeulich@xxxxxxxx>]

The caching isn't actually implemented here, this is just setting the
stage.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -2572,6 +2572,18 @@ void hvm_dump_emulation_state(const char
            hvmemul_ctxt->insn_buf);
 }
 
+bool hvmemul_read_cache(const struct hvmemul_cache *cache, paddr_t gpa,
+                        unsigned int level, void *buffer, unsigned int size)
+{
+    return false;
+}
+
+void hvmemul_write_cache(struct hvmemul_cache *cache, paddr_t gpa,
+                         unsigned int level, const void *buffer,
+                         unsigned int size)
+{
+}
+
 /*
  * Local variables:
  * mode: C
--- a/xen/arch/x86/mm/guest_walk.c
+++ b/xen/arch/x86/mm/guest_walk.c
@@ -94,6 +94,7 @@ guest_walk_tables(struct vcpu *v, struct
     guest_l4e_t *l4p;
 #endif
     uint32_t gflags, rc;
+    paddr_t gpa;
     unsigned int leaf_level;
     p2m_query_t qt = P2M_ALLOC | P2M_UNSHARE;
 
@@ -134,7 +135,15 @@ guest_walk_tables(struct vcpu *v, struct
     /* Get the l4e from the top level table and check its flags*/
     gw->l4mfn = top_mfn;
     l4p = (guest_l4e_t *) top_map;
-    gw->l4e = l4p[guest_l4_table_offset(gla)];
+    gpa = gfn_to_gaddr(top_gfn) +
+          guest_l4_table_offset(gla) * sizeof(guest_l4e_t);
+    if ( !cache ||
+         !hvmemul_read_cache(cache, gpa, 4, &gw->l4e, sizeof(gw->l4e)) )
+    {
+        gw->l4e = l4p[guest_l4_table_offset(gla)];
+        if ( cache )
+            hvmemul_write_cache(cache, gpa, 4, &gw->l4e, sizeof(gw->l4e));
+    }
     gflags = guest_l4e_get_flags(gw->l4e);
     if ( !(gflags & _PAGE_PRESENT) )
         goto out;
@@ -164,7 +173,15 @@ guest_walk_tables(struct vcpu *v, struct
     }
 
     /* Get the l3e and check its flags*/
-    gw->l3e = l3p[guest_l3_table_offset(gla)];
+    gpa = gfn_to_gaddr(guest_l4e_get_gfn(gw->l4e)) +
+          guest_l3_table_offset(gla) * sizeof(guest_l3e_t);
+    if ( !cache ||
+         !hvmemul_read_cache(cache, gpa, 3, &gw->l3e, sizeof(gw->l3e)) )
+    {
+        gw->l3e = l3p[guest_l3_table_offset(gla)];
+        if ( cache )
+            hvmemul_write_cache(cache, gpa, 3, &gw->l3e, sizeof(gw->l3e));
+    }
     gflags = guest_l3e_get_flags(gw->l3e);
     if ( !(gflags & _PAGE_PRESENT) )
         goto out;
@@ -216,7 +233,16 @@ guest_walk_tables(struct vcpu *v, struct
 #else /* PAE only... */
 
     /* Get the l3e and check its flag */
-    gw->l3e = ((guest_l3e_t *)top_map)[guest_l3_table_offset(gla)];
+    gpa = gfn_to_gaddr(top_gfn) + ((unsigned long)top_map & ~PAGE_MASK) +
+          guest_l3_table_offset(gla) * sizeof(guest_l3e_t);
+    if ( !cache ||
+         !hvmemul_read_cache(cache, gpa, 3, &gw->l3e, sizeof(gw->l3e)) )
+    {
+        gw->l3e = ((guest_l3e_t *)top_map)[guest_l3_table_offset(gla)];
+        if ( cache )
+            hvmemul_write_cache(cache, gpa, 3, &gw->l3e, sizeof(gw->l3e));
+    }
+
     gflags = guest_l3e_get_flags(gw->l3e);
     if ( !(gflags & _PAGE_PRESENT) )
         goto out;
@@ -242,18 +268,24 @@ guest_walk_tables(struct vcpu *v, struct
         goto out;
     }
 
-    /* Get the l2e */
-    gw->l2e = l2p[guest_l2_table_offset(gla)];
-
 #else /* 32-bit only... */
 
-    /* Get l2e from the top level table */
     gw->l2mfn = top_mfn;
     l2p = (guest_l2e_t *) top_map;
-    gw->l2e = l2p[guest_l2_table_offset(gla)];
 
 #endif /* All levels... */
 
+    /* Get the l2e */
+    gpa = gfn_to_gaddr(top_gfn) +
+          guest_l2_table_offset(gla) * sizeof(guest_l2e_t);
+    if ( !cache ||
+         !hvmemul_read_cache(cache, gpa, 2, &gw->l2e, sizeof(gw->l2e)) )
+    {
+        gw->l2e = l2p[guest_l2_table_offset(gla)];
+        if ( cache )
+            hvmemul_write_cache(cache, gpa, 2, &gw->l2e, sizeof(gw->l2e));
+    }
+
     /* Check the l2e flags. */
     gflags = guest_l2e_get_flags(gw->l2e);
     if ( !(gflags & _PAGE_PRESENT) )
@@ -335,7 +367,17 @@ guest_walk_tables(struct vcpu *v, struct
         gw->pfec |= rc & PFEC_synth_mask;
         goto out;
     }
-    gw->l1e = l1p[guest_l1_table_offset(gla)];
+
+    gpa = gfn_to_gaddr(top_gfn) +
+          guest_l1_table_offset(gla) * sizeof(guest_l1e_t);
+    if ( !cache ||
+         !hvmemul_read_cache(cache, gpa, 1, &gw->l1e, sizeof(gw->l1e)) )
+    {
+        gw->l1e = l1p[guest_l1_table_offset(gla)];
+        if ( cache )
+            hvmemul_write_cache(cache, gpa, 1, &gw->l1e, sizeof(gw->l1e));
+    }
+
     gflags = guest_l1e_get_flags(gw->l1e);
     if ( !(gflags & _PAGE_PRESENT) )
         goto out;
--- a/xen/include/asm-x86/hvm/emulate.h
+++ b/xen/include/asm-x86/hvm/emulate.h
@@ -98,6 +98,13 @@ int hvmemul_do_pio_buffer(uint16_t port,
                           uint8_t dir,
                           void *buffer);
 
+struct hvmemul_cache;
+bool hvmemul_read_cache(const struct hvmemul_cache *, paddr_t gpa,
+                        unsigned int level, void *buffer, unsigned int size);
+void hvmemul_write_cache(struct hvmemul_cache *, paddr_t gpa,
+                         unsigned int level, const void *buffer,
+                         unsigned int size);
+
 void hvm_dump_emulation_state(const char *loglvl, const char *prefix,
                               struct hvm_emulate_ctxt *hvmemul_ctxt, int rc);
 




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