Re: [Qemu-devel] [PATCH v2 07/18] nvdimm: reserve address range for NVDIMM

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

On 09/04/2015 08:02 PM, Igor Mammedov wrote:
> On Fri, 14 Aug 2015 22:52:00 +0800
> Xiao Guangrong <guangrong.xiao@linux.intel.com> wrote:
>
>> NVDIMM reserves all the free range above 4G to do:
>> - Persistent Memory (PMEM) mapping
>> - implement NVDIMM ACPI device _DSM method
>>
>> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
>> ---
>>   hw/i386/pc.c               | 12 ++++++++++--
>>   hw/mem/nvdimm/pc-nvdimm.c  | 13 +++++++++++++
>>   include/hw/mem/pc-nvdimm.h |  1 +
>>   3 files changed, 24 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>> index 7661ea9..41af6ea 100644
>> --- a/hw/i386/pc.c
>> +++ b/hw/i386/pc.c
>> @@ -64,6 +64,7 @@
>>   #include "hw/pci/pci_host.h"
>>   #include "acpi-build.h"
>>   #include "hw/mem/pc-dimm.h"
>> +#include "hw/mem/pc-nvdimm.h"
>>   #include "qapi/visitor.h"
>>   #include "qapi-visit.h"
>>
>> @@ -1302,6 +1303,7 @@ FWCfgState *pc_memory_init(MachineState *machine,
>>       MemoryRegion *ram_below_4g, *ram_above_4g;
>>       FWCfgState *fw_cfg;
>>       PCMachineState *pcms = PC_MACHINE(machine);
>> +    ram_addr_t offset;
>>
>>       assert(machine->ram_size == below_4g_mem_size + above_4g_mem_size);
>>
>> @@ -1339,6 +1341,8 @@ FWCfgState *pc_memory_init(MachineState *machine,
>>           exit(EXIT_FAILURE);
>>       }
>>
>> +    offset = 0x100000000ULL + above_4g_mem_size;
>> +
>>       /* initialize hotplug memory address space */
>>       if (guest_info->has_reserved_memory &&
>>           (machine->ram_size < machine->maxram_size)) {
>> @@ -1358,8 +1362,7 @@ FWCfgState *pc_memory_init(MachineState *machine,
>>               exit(EXIT_FAILURE);
>>           }
>>
>> -        pcms->hotplug_memory.base =
>> -            ROUND_UP(0x100000000ULL + above_4g_mem_size, 1ULL << 30);
>> +        pcms->hotplug_memory.base = ROUND_UP(offset, 1ULL << 30);
>>
>>           if (pcms->enforce_aligned_dimm) {
>>               /* size hotplug region assuming 1G page max alignment per slot */
>> @@ -1377,8 +1380,13 @@ FWCfgState *pc_memory_init(MachineState *machine,
>>                              "hotplug-memory", hotplug_mem_size);
>>           memory_region_add_subregion(system_memory, pcms->hotplug_memory.base,
>>                                       &pcms->hotplug_memory.mr);
>> +
>> +        offset = pcms->hotplug_memory.base + hotplug_mem_size;
>>       }
>>
>> +     /* all the space left above 4G is reserved for NVDIMM. */
>> +    pc_nvdimm_reserve_range(offset);
> I'd drop 'offset' in this patch and just use:
>    foo(pcms->hotplug_memory.base + hotplug_mem_size)
>

That works only if hotplug is used... however we can enable nvdimm separately.

>> +
>>       /* Initialize PC system firmware */
>>       pc_system_firmware_init(rom_memory, guest_info->isapc_ram_fw);
>>
>> diff --git a/hw/mem/nvdimm/pc-nvdimm.c b/hw/mem/nvdimm/pc-nvdimm.c
>> index a53d235..7a270a8 100644
>> --- a/hw/mem/nvdimm/pc-nvdimm.c
>> +++ b/hw/mem/nvdimm/pc-nvdimm.c
>> @@ -24,6 +24,19 @@
>>
>>   #include "hw/mem/pc-nvdimm.h"
>>
>> +#define PAGE_SIZE      (1UL << 12)
>> +
>> +static struct nvdimms_info {
>> +    ram_addr_t current_addr;
>> +} nvdimms_info;
> no globals please, so far it looks like pcms->hotplug_memory
> so add asimmilar nvdimm_memory field to PCMachineState
>

Okay, it's good to me.

>> +
>> +/* the address range [offset, ~0ULL) is reserved for NVDIMM. */
>> +void pc_nvdimm_reserve_range(ram_addr_t offset)
> do you plan to reuse this function, if not then just inline it at call site

I prefer it as a inline function and move it to the nvdimm.h file since it's easier
to port it to other platforms - avoid to find the pieces of code related to nvdimm
in x86 arch and only needed to implement the functions in nvdimm.h.

>
>> +{
>> +    offset = ROUND_UP(offset, PAGE_SIZE);
> I'd suggest round up to 1Gb as we do with mem hotplug

Okay, good to me.

Really appreciate for all your time/comment in the whole patchset, Igor!