Re: [PATCH v1 2/3] memory-device: Factor out device memory initialization into memory_devices_init()

[David Hildenbrand <david@redhat.com>]

On 25.05.23 15:30, Philippe Mathieu-Daudé wrote:
> Hi David,
> 
> On 23/5/23 20:51, David Hildenbrand wrote:
>> Let's factor the common setup out, to prepare for further changes.
>>
>> On arm64, we'll add the subregion to system RAM now earlier -- which
>> shouldn't matter, because the system RAM memory region should already be
>> alive at that point.
>>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>>    hw/arm/virt.c                  |  9 +--------
>>    hw/i386/pc.c                   | 17 ++++++-----------
>>    hw/loongarch/virt.c            | 14 ++++----------
>>    hw/mem/memory-device.c         | 20 ++++++++++++++++++++
>>    hw/ppc/spapr.c                 | 15 ++++++---------
>>    include/hw/mem/memory-device.h |  2 ++
>>    6 files changed, 39 insertions(+), 38 deletions(-)
> 
> Split in boring 'first add method then use it for each arch'
> would be easier to review.

Right, I agree if I'd be touching more code (I consider this fairly 
minimal and straight-forward refactoring).

> 
>> diff --git a/hw/mem/memory-device.c b/hw/mem/memory-device.c
>> index 6c025b02c1..d99ceb621a 100644
>> --- a/hw/mem/memory-device.c
>> +++ b/hw/mem/memory-device.c
>> @@ -17,6 +17,7 @@
>>    #include "qemu/range.h"
>>    #include "hw/virtio/vhost.h"
>>    #include "sysemu/kvm.h"
>> +#include "exec/address-spaces.h"
>>    #include "trace.h"
>>    
>>    static gint memory_device_addr_sort(gconstpointer a, gconstpointer b)
>> @@ -333,6 +334,25 @@ uint64_t memory_device_get_region_size(const MemoryDeviceState *md,
>>        return memory_region_size(mr);
>>    }
>>    
>> +void memory_devices_init(MachineState *ms, hwaddr base, uint64_t size)
>> +{
>> +    g_assert(!ms->device_memory);
>> +    ms->device_memory = g_new0(DeviceMemoryState, 1);
>> +    ms->device_memory->base = base;
>> +
>> +    /*
>> +     * See memory_device_get_free_addr(): An empty device memory region
>> +     * means "this machine supports memory devices, but they are not enabled".
>> +     */
>> +    if (size > 0) {
>> +        memory_region_init(&ms->device_memory->mr, OBJECT(ms), "device-memory",
>> +                           size);
>> +        memory_region_add_subregion(get_system_memory(),
>> +                                    ms->device_memory->base,
>> +                                    &ms->device_memory->mr);
> 
> What about always init/register and set if enabled?
> 
>     memory_region_set_enabled(&ms->device_memory->mr, size > 0);
> 
> Otherwise why allocate ms->device_memory?

We have right now:

ms->device_memory not allocated: no support
ms->device_memory->mr with size 0: not enabled
ms->device_memory->mr with size > 0: enabled

Let me see if initializing a memory region with size 0 (and adding a 
subregion with size 0) works.

Thanks!

-- 
Thanks,

David / dhildenb