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

[Jan Kiszka <jan.kiszka@web.de>]

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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 <bdwheele@indiana.edu>
> 
> --- vl.c.orig	2009-04-10 10:01:52.000000000 -0400
> +++ vl.c	2009-04-10 10:13:33.000000000 -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 +304,33 @@
>  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) 
> +{
> +  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) {
> +    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.

> +#ifdef DEBUG_IOPORT_FIND
> +    printf("Initializing ioport page %d to: %p\n", page, ioport[page]);
> +#endif
> +  }
> +  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 +338,11 @@
>          default_ioport_readw,
>          default_ioport_readl
>      };
> -    IOPortReadFunc *func = ioport_read_table[index][address];
> +    ioport_t *p = ioport_find(address);
> +    IOPortReadFunc *func = p->read[index];
>      if (!func)
>          func = default_func[index];
> -    return func(ioport_opaque[address], address);
> +    return func(p->opaque, address);
>  }
>  
>  static void ioport_write(int index, uint32_t address, uint32_t data)
> @@ -308,10 +352,11 @@
>          default_ioport_writew,
>          default_ioport_writel
>      };
> -    IOPortWriteFunc *func = ioport_write_table[index][address];
> +    ioport_t *p = ioport_find(address);
> +    IOPortWriteFunc *func = p->write[index];
>      if (!func)
>          func = default_func[index];
> -    func(ioport_opaque[address], address, data);
> +    func(p->opaque, address, data);
>  }
>  
>  static uint32_t default_ioport_readb(void *opaque, uint32_t address)
> @@ -378,10 +423,11 @@
>          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);
> +        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 +449,11 @@
>          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);
> +        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 +463,16 @@
>      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);
> +        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;
>      }
>  }
>  
> 

Jan


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