Re: [Qemu-arm] [Qemu-devel] [PATCH v6 14/18] hw/arm/virt: Allocate device_memory

[Auger Eric]

Hi Igor,

On 2/21/19 10:36 AM, Igor Mammedov wrote:
> On Tue, 19 Feb 2019 16:53:22 +0100
> Auger Eric <address@hidden> wrote:
> 
>> Hi Igor,
>>
>> On 2/18/19 10:31 AM, Igor Mammedov wrote:
>>> On Tue,  5 Feb 2019 18:33:02 +0100
>>> Eric Auger <address@hidden> wrote:
>>>   
>>>> The device memory region is located after the initial RAM.
>>>> its start/size are 1GB aligned.
>>>>
>>>> Signed-off-by: Eric Auger <address@hidden>
>>>> Signed-off-by: Kwangwoo Lee <address@hidden>
>>>>
>>>> ---
>>>> v4 -> v5:
>>>> - device memory set after the initial RAM
>>>>
>>>> v3 -> v4:
>>>> - remove bootinfo.device_memory_start/device_memory_size
>>>> - rename VIRT_HOTPLUG_MEM into VIRT_DEVICE_MEM
>>>> ---
>>>>  hw/arm/virt.c | 36 ++++++++++++++++++++++++++++++++++++
>>>>  1 file changed, 36 insertions(+)
>>>>
>>>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>>>> index 783468ba77..b683902991 100644
>>>> --- a/hw/arm/virt.c
>>>> +++ b/hw/arm/virt.c
>>>> @@ -61,6 +61,7 @@
>>>>  #include "hw/arm/smmuv3.h"
>>>>  #include "hw/mem/pc-dimm.h"
>>>>  #include "hw/mem/nvdimm.h"
>>>> +#include "hw/acpi/acpi.h"
>>>>  
>>>>  #define DEFINE_VIRT_MACHINE_LATEST(major, minor, latest) \
>>>>      static void virt_##major##_##minor##_class_init(ObjectClass *oc, \
>>>> @@ -1260,6 +1261,37 @@ static void create_secure_ram(VirtMachineState *vms,
>>>>      g_free(nodename);
>>>>  }
>>>>  
>>>> +static void create_device_memory(VirtMachineState *vms, MemoryRegion 
>>>> *sysmem)
>>>> +{
>>>> +    MachineState *ms = MACHINE(vms);
>>>> +    uint64_t device_memory_size = ms->maxram_size - ms->ram_size;  
>>> should size it with 1Gb alignment per slot from the start (to avoid x86 
>>> mistakes),
>>> see enforce_aligned_dimm usage and associated commit for more details  
>> I don't understand the computation done in pc machine. eventually we are
>> likely to have more device memory than requested by the user. Why don't
>> we check (machine->maxram_size - machine->ram_size) >=
>> machine->ram_slots * GiB
>> instead of adding 1GiB/slot to the initial user requirements?
>>
>> Also machine->maxram_size - machine->ram_size is checked to be aligned
>> with TARGET_PAGE_SIZE. Is TARGET_PAGE_SIZE representative of the guest
>> PAGE in accelerated mode? Is it valid ro require an alignment on 1GB
>> boundary as I do in this patch?
> See commit 085f8e88b for explanation,
> What we are basically are doing there is sizing hotpluggbale address space
> to allow max possible huge page aligned DIMM to be successfully plugged in
> even if address space if fragmented.
In v7, I also added ram_slots * GiB to (maxram_size - ram_size).

Thanks

Eric
> 
>>
>>>   
>>>> +    uint64_t align = GiB;
>>>> +
>>>> +    if (!device_memory_size) {
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    if (ms->ram_slots > ACPI_MAX_RAM_SLOTS) {
>>>> +        error_report("unsupported number of memory slots: %"PRIu64,
>>>> +                     ms->ram_slots);
>>>> +        exit(EXIT_FAILURE);
>>>> +    }
>>>> +
>>>> +    if (QEMU_ALIGN_UP(ms->maxram_size, align) != ms->maxram_size) {
>>>> +        error_report("maximum memory size must be aligned to multiple of 
>>>> 0x%"
>>>> +                     PRIx64, align);
>>>> +        exit(EXIT_FAILURE);
>>>> +    }
>>>> +
>>>> +    ms->device_memory = g_malloc0(sizeof(*ms->device_memory));
>>>> +    ms->device_memory->base = QEMU_ALIGN_UP(GiB + ms->ram_size, GiB);  
>>>                                                ^^^ where does this come 
>>> from?  
>> OK, introduced RAMBASE macro
>>
>> Thanks
>>
>> Eric
>>>
>>>   
>>>> +
>>>> +    memory_region_init(&ms->device_memory->mr, OBJECT(vms),
>>>> +                       "device-memory", device_memory_size);
>>>> +    memory_region_add_subregion(sysmem, ms->device_memory->base,
>>>> +                                &ms->device_memory->mr);
>>>> +}
>>>> +
>>>>  static void *machvirt_dtb(const struct arm_boot_info *binfo, int 
>>>> *fdt_size)
>>>>  {
>>>>      const VirtMachineState *board = container_of(binfo, VirtMachineState,
>>>> @@ -1569,6 +1601,10 @@ static void machvirt_init(MachineState *machine)
>>>>                                           machine->ram_size);
>>>>      memory_region_add_subregion(sysmem, vms->memmap[VIRT_MEM].base, ram);
>>>>  
>>>> +    if (vms->extended_memmap) {
>>>> +        create_device_memory(vms, sysmem);
>>>> +    }
>>>> +
>>>>      create_flash(vms, sysmem, secure_sysmem ? secure_sysmem : sysmem);
>>>>  
>>>>      create_gic(vms, pic);  
>>>   
>>
> 
>