[Qemu-devel] Re: [PATCH 1/6] Use correct types to enable > 2G support

[Fabrice Bellard <fabrice@bellard.org>]

Anthony Liguori wrote:
> KVM supports more than 2GB of memory for x86_64 hosts.  The following patch
> fixes a number of type related issues where int's were being used when they
> shouldn't have been.  It also introduces CMOS support so the BIOS can build
> the appropriate e820 tables.

 > [...]
> +    /* above 4giga memory allocation */
> +    if (above_4g_mem_size > 0) {
> +        ram_addr = qemu_ram_alloc(above_4g_mem_size);
> +        cpu_register_physical_memory(0x100000000, above_4g_mem_size, ram_addr);
> +    }
> +

Why do you need this ? All the RAM can be registered with a single call. 
  I fear you need to do that because of KVM RAM handling limitations.

> Index: qemu/osdep.c
> ===================================================================
> --- qemu.orig/osdep.c	2008-01-30 13:47:00.000000000 -0600
> +++ qemu/osdep.c	2008-01-30 13:47:31.000000000 -0600
> @@ -113,7 +113,7 @@
>              int64_t free_space;
>              int ram_mb;
>  
> -            extern int ram_size;
> +            extern int64_t ram_size;
>              free_space = (int64_t)stfs.f_bavail * stfs.f_bsize;
>              if ((ram_size + 8192 * 1024) >= free_space) {
>                  ram_mb = (ram_size / (1024 * 1024));
> @@ -202,7 +202,7 @@
>  #ifdef _BSD
>      return valloc(size);
>  #else
> -    return memalign(4096, size);
> +    return memalign(TARGET_PAGE_SIZE, size);
>  #endif
>  }

No fully correct because it is intended to be the host page size.

> +extern int64_t ram_size;

I agree with the fact that ram_size should be 64 bit. Maybe each machine 
could test the value and emit an error message if it is too big. Maybe 
an uint64_t would be better though.

Fabrice.