Re: [PATCH] KVM: VMX: Move private memory slot position

[Sheng Yang <sheng@linux.intel.com>]

On Thursday 16 October 2008 16:26:07 Avi Kivity wrote:
> Yang, Sheng wrote:
> > I've found the reason... It's because that kvm_mmu_page->slot_bitmap is
> > unsigned long, and if use KVM_MEMORY_SLOTS + xxx, it would beyond 32 in
> > pae, then memory corrupted.
> >
> > But reduce supported memory slot number to 28 or extend slot_bitmap, or
> > other methods? Slot_bitmap have bitops, so keep unsigned long would be
> > better... Now reduce supported memory slot number seems reasonable to me.
>
> We could change it to DECLARE_BITMAP, and thus support >= 32 slots even
> on i386.  But I agree that 28 slots would be sufficient.

DECLARE_BITMAP looks like a flexible solution, I forgot it...(and I also don't 
like to change a lot of macro in kernel and userspace). I will post the patch 
soon.

>
> > (I also want to have this fix into 2.6.28, for some device would easily
> > overlapped with current private memory slot)
>
> I've been thinking that we can get rid of internal slots, by placing the
> TSS, real mode identity map, and APIC access page in the bios.  Of
> course we would need a new ioctl to let the kernel know where the
> scratch memory is located and how much of it is available.
>

How about put into userspace e.g. pc_init()? I think more easy than keeping 
bios sync with KVM. Anyway, vmx specific thing would become generic. I'd like 
to keep it as what it is at least for now...

--
regards
Yang, Sheng