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

[Auger Eric <eric.auger@redhat.com>]

Hi Igor,

On 2/18/19 10:31 AM, Igor Mammedov wrote:
> On Tue,  5 Feb 2019 18:33:02 +0100
> Eric Auger <eric.auger@redhat.com> wrote:
> 
>> The device memory region is located after the initial RAM.
>> its start/size are 1GB aligned.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> Signed-off-by: Kwangwoo Lee <kwangwoo.lee@sk.com>
>>
>> ---
>> 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?

> 
>> +    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);
>