Re: [Qemu-arm] [RFC PATCH 1/3] hw/arm/virt: add hotplug memory support

[Peter Maydell]

On 1 August 2016 at 08:46, Igor Mammedov <address@hidden> wrote:
> On Mon, 1 Aug 2016 00:35:35 +0000
> "address@hidden" <address@hidden> wrote:

>> > > +/* 1GB alignment for hotplug memory region */
>> > > +#define ARCH_VIRT_HOTPLUG_MEM_ALIGN (1ULL << 30)
>> >
>> > Where does the 1GB alignment come from? Why do we need 1GB
>> > alignment for the base but only 1KB alignment for the size?
>>
>> The alignment value of hotplug_memory.base referred from i386 pc.c and ppc 
>> spapr.c.
>> Could you suggest a proper range for this?

> Base alignment comes from max supported hugepage size,

Max hugepage size for any host? (if so, should be defined
in a common header somewhere)
Max hugepage size for ARM hosts? (if so, why is TCG
different from KVM?, and should still be in a common
header somewhere)

> while
> size alignment should depend on backend's page size

Which page size do you have in mind here? TARGET_PAGE_SIZE
is often not the right answer, since it doesn't
correspond either to the actual page size being used
by the host kernel or to the actual page size used
by the guest kernel...

thanks
-- PMM