Re: [kvm-ppc-devel] RFC/patch portability: split kvm_vm_ioctl v2

Avi Kivity
2007-10-26T11:47:14Z

Carsten Otte wrote:
> Avi Kivity wrote:
>> Why aren't memory slots common too? Only their number is different,
>> while the implementation is the same.
> Your approach makes the meaning of memory slot somewhat useless on
> s390, if that one may be sparse and may be result of different
> allocations: On x86, there has to be one memory slot per allocation,
> versus on s390 there has to be exactly one memory slot with multiple
> allocations behind.

No, a memory slot can span multiple backing stores. But it must be
contiguous in both the host userspace and guest physical address spaces.

>
> For userspace that means, with your approach it has to do total
> different memory setup for different archs _if_ it wants to use
> multiple allocations and/or sparse:
> - on x86 it does allocations to random userspace address, and
> registers each of them as memory slot
> - on s390 it does allocations to a specific address layout similar to
> the guest, and registers only one memory slot for the whole thing
>
> With Izik's approach however, this is transparent to userspace: it has
> multiple memory slots, one per allocation. Regardless of the CPU
> architecture.

You can do this with the current memory slots as well. Although I'm
feeling that I misunderstood Izik's idea. I'll go talk to him.

--
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