Re: 2 CPU Conformance Issue in KVM/x86

Paolo Bonzini
2015-03-10T10:47:17Z

On 09/03/2015 20:49, Avi Kivity wrote:
>>>
>> Yes, and it checked that MAXPHYADDR != 52 before. If you want to set
>> only one bit, making that bit 51 makes sense anyway for simplicity, so
>> it is still 99.9% academic. Once processors appear with MAXPHYADDR =
>> 52, the remaining 0.1% will become more relevant.
>>
>> The current limit is IIRC 46 or 48 (on Haswell Xeons).
>
> It will be interesting to have processors with 52 bits of physical
> address and 48 bits of virtual address. HIGHMEM for x86_64? Or 5-level
> page tables?

I wonder why Intel chose exactly 52... HIGHMEM seems more likely than
5-level page tables. Certainly it wouldn't need hacks like Ingo's 4G-4G.

> 50 bits == 1 PiB. That's quite an amount of RAM.

Not that 64 TiB is not "quite an amount of RAM". :)

Paolo