Re: 2 CPU Conformance Issue in KVM/x86

Avi Kivity
2015-03-10T20:38:28Z

On 03/10/2015 12:47 PM, Paolo Bonzini wrote:
>
> 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.

My bitcoins are on 5-level page tables. HIGHMEM is too much pain.

>> 50 bits == 1 PiB. That's quite an amount of RAM.
> Not that 64 TiB is not "quite an amount of RAM". :)
>
>

Depends on how many browser tabs you have open, I guess.