Re: [Qemu-devel] Re: [PATCH] two level table for IO port lookup [Patch updated]

[Brian Wheeler]

On Fri, 2009-04-10 at 17:17 +0200, Jan Kiszka wrote:
> Brian Wheeler wrote:
> > The alpha architecture uses 24 bits for the io port address so this
> > patch adds a two level table and puts the IO port data into a
> > struct...because sizeof(void *) * 7 * 16777216 is nearly a 1G on my
> > workstation.
> > 
> > I've set the alpha target to use a 12/12 split and everything else to
> > use 8/8.  
> > 
> > 
> > 
> > 
> > Signed-off-by: Brian Wheeler <address@hidden>
> > 

> > +  if(ioport[page]==NULL) {
> > +    ioport[page]=calloc((1<<IOPORT_PAGESIZE), sizeof(ioport_t));
> 
> As you use ioport_find also for guest-driven port access, doing
> allocation here is a bad idea. Consider a guest that probes the whole io
> address space of your alpha box: you would end up with the same gig
> being allocated that you try to avoid with this approach.
> 
> IOW: Only allocate on handler registration. On unsuccessful lookup, just
> call the proper default handler.
> 

Good point.  This patch does that:  there's an allocate flag which is
set only by the registration calls so only they will allocate memory.

Signed-off-by: Brian Wheeler <address@hidden>


--- vl.c.orig   2009-04-10 10:01:52.000000000 -0400
+++ vl.c        2009-04-10 11:40:27.000000000 -0400
@@ -168,7 +168,7 @@
 //#define DEBUG_IOPORT
 //#define DEBUG_NET
 //#define DEBUG_SLIRP
-
+//#define DEBUG_IOPORT_FIND
 
 #ifdef DEBUG_IOPORT
 #  define LOG_IOPORT(...) qemu_log_mask(CPU_LOG_IOPORT, ## __VA_ARGS__)
@@ -184,14 +184,30 @@
 /* Max number of bluetooth switches on the commandline.  */
 #define MAX_BT_CMDLINE 10
 
-/* XXX: use a two level table to limit memory usage */
-#define MAX_IOPORTS 65536
-
 const char *bios_dir = CONFIG_QEMU_SHAREDIR;
 const char *bios_name = NULL;
-static void *ioport_opaque[MAX_IOPORTS];
-static IOPortReadFunc *ioport_read_table[3][MAX_IOPORTS];
-static IOPortWriteFunc *ioport_write_table[3][MAX_IOPORTS];
+
+struct ioport {
+       void *opaque;
+       IOPortReadFunc *read[3];
+       IOPortWriteFunc *write[3];
+};
+typedef struct ioport ioport_t;
+
+#ifdef TARGET_ALPHA
+#define IOPORT_MAXBITS 24
+#define IOPORT_PAGESIZE 12
+#else
+#define IOPORT_MAXBITS 16
+#define IOPORT_PAGESIZE 8
+#endif
+
+#define IOPORT_ENTRYMASK ((1<<IOPORT_PAGESIZE)-1)
+#define IOPORT_PAGEMASK ~IOPORT_ENTRYMASK
+#define MAX_IOPORTS (1<<IOPORT_MAXBITS)
+
+void *ioport[1<<(IOPORT_MAXBITS-IOPORT_PAGESIZE)];
+
 /* Note: drives_table[MAX_DRIVES] is a dummy block driver if none available
    to store the VM snapshots */
 DriveInfo drives_table[MAX_DRIVES+1];
@@ -288,6 +304,37 @@
 static IOPortReadFunc default_ioport_readb, default_ioport_readw, 
default_ioport_readl;
 static IOPortWriteFunc default_ioport_writeb, default_ioport_writew, 
default_ioport_writel;
 
+
+static inline ioport_t *ioport_find(uint32_t address, int allocate) 
+{
+  uint32_t page = (address & IOPORT_PAGEMASK) >> IOPORT_PAGESIZE;
+  uint32_t entry = address & IOPORT_ENTRYMASK;
+  if(address >= (1<<IOPORT_MAXBITS))
+    hw_error("Maximum port # for this architecture is %d.  Port %d requested.",
+            (1<<IOPORT_MAXBITS)-1, address);
+  
+  if(ioport[page]==NULL) {
+    if(allocate) {
+      ioport[page]=calloc((1<<IOPORT_PAGESIZE), sizeof(ioport_t));
+#ifdef DEBUG_IOPORT_FIND
+    printf("Initializing ioport page %d to: %p\n", page, ioport[page]);
+#endif
+    } else {
+      return NULL;
+    }
+  }
+  ioport_t *p = (ioport_t *)(ioport[page] + entry * sizeof(ioport_t));
+
+#ifdef DEBUG_IOPORT_FIND
+  printf("port find %d:  page=%d, address=%p, entry=%d, address=%p\n", 
+        address, page, ioport[page], entry, p);
+  printf("  data: %p\n", p->opaque);
+  printf("  read: %p, %p, %p\n", p->read[0], p->read[1], p->read[2]);
+  printf(" write: %p, %p, %p\n", p->write[0], p->write[1], p->write[2]);
+#endif
+  return p;
+}
+
 static uint32_t ioport_read(int index, uint32_t address)
 {
     static IOPortReadFunc *default_func[3] = {
@@ -295,10 +342,16 @@
         default_ioport_readw,
         default_ioport_readl
     };
-    IOPortReadFunc *func = ioport_read_table[index][address];
+    ioport_t *p = ioport_find(address, 0);
+    IOPortReadFunc *func = NULL;
+    void *opaque = NULL;
+    if(p) {
+      func = p->read[index];
+      opaque = p->opaque;
+    }
     if (!func)
         func = default_func[index];
-    return func(ioport_opaque[address], address);
+    return func(opaque, address);
 }
 
 static void ioport_write(int index, uint32_t address, uint32_t data)
@@ -308,10 +361,16 @@
         default_ioport_writew,
         default_ioport_writel
     };
-    IOPortWriteFunc *func = ioport_write_table[index][address];
+    ioport_t *p = ioport_find(address, 0);
+    IOPortWriteFunc *func = NULL;
+    void *opaque = NULL;
+    if(p) {
+      func = p->write[index];
+      opaque = p->opaque;
+    }
     if (!func)
         func = default_func[index];
-    func(ioport_opaque[address], address, data);
+    func(opaque, address, data);
 }
 
 static uint32_t default_ioport_readb(void *opaque, uint32_t address)
@@ -378,10 +437,11 @@
         return -1;
     }
     for(i = start; i < start + length; i += size) {
-        ioport_read_table[bsize][i] = func;
-        if (ioport_opaque[i] != NULL && ioport_opaque[i] != opaque)
+      ioport_t *p = ioport_find(i, 1);
+        p->read[bsize] = func;
+        if (p->opaque != NULL && p->opaque != opaque)
             hw_error("register_ioport_read: invalid opaque");
-        ioport_opaque[i] = opaque;
+        p->opaque = opaque;
     }
     return 0;
 }
@@ -403,10 +463,11 @@
         return -1;
     }
     for(i = start; i < start + length; i += size) {
-        ioport_write_table[bsize][i] = func;
-        if (ioport_opaque[i] != NULL && ioport_opaque[i] != opaque)
+        ioport_t *p = ioport_find(i, 1);
+        p->write[bsize] = func;
+        if (p->opaque != NULL && p->opaque != opaque)
             hw_error("register_ioport_write: invalid opaque");
-        ioport_opaque[i] = opaque;
+        p->opaque = opaque;
     }
     return 0;
 }
@@ -416,15 +477,16 @@
     int i;
 
     for(i = start; i < start + length; i++) {
-        ioport_read_table[0][i] = default_ioport_readb;
-        ioport_read_table[1][i] = default_ioport_readw;
-        ioport_read_table[2][i] = default_ioport_readl;
-
-        ioport_write_table[0][i] = default_ioport_writeb;
-        ioport_write_table[1][i] = default_ioport_writew;
-        ioport_write_table[2][i] = default_ioport_writel;
+        ioport_t *p = ioport_find(i, 1);
+        p->read[0] = default_ioport_readb;
+        p->read[1] = default_ioport_readw;
+        p->read[2] = default_ioport_readl;
+
+        p->write[0] = default_ioport_writeb;
+        p->write[1] = default_ioport_writew;
+        p->write[2] = default_ioport_writel;
 
-        ioport_opaque[i] = NULL;
+        p->opaque = NULL;
     }
 }