Re: [Qemu-devel] [PATCH] s390x: initialize virtio dev region

[Alexander Graf]

On 10.11.2011, at 02:36, Peter Maydell wrote:

> On 10 November 2011 01:19, Alexander Graf <address@hidden> wrote:
>> @@ -184,6 +186,13 @@ static void s390_init(ram_addr_t my_ram_size,
>>     memory_region_init_ram(ram, NULL, "s390.ram", my_ram_size);
>>     memory_region_add_subregion(sysmem, 0, ram);
>> 
>> +    /* clear virtio region */
>> +    virtio_region_len = my_ram_size - ram_size;
>> +    virtio_region = cpu_physical_memory_map(ram_size, &virtio_region_len, 
>> true);
>> +    memset(virtio_region, 0, virtio_region_len);
>> +    cpu_physical_memory_unmap(virtio_region, virtio_region_len, 1,
>> +                              virtio_region_len);
>> +
> 
> This looks a bit fishy -- cpu_physical_memory_map() takes a
> target_phys_addr_t but you're passing it a ram_addr_t.

Meh. Always those types ... :)

> Also isn't this second-guessing the ram_addr_t of the region allocated
> inside memory_region_init_ram() ?

Not sure I understand? On s390-virtio we have to following ram layout:

[ ----- RAM ---- | --- virtio device structs --- ]

The size of the latter is added to my_ram_size by s390_virtio_bus_init. All I'm 
trying to do is make sure that this latter part of RAM is always 0, while the 
first part can still be dynamically allocated.


Alex