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

["Yang, Sheng" <sheng.yang@intel.com>]

On Saturday 13 September 2008 16:55:27 Avi Kivity wrote:
> Avi Kivity wrote:
> > Yang, Sheng wrote:
> >> On Thursday 04 September 2008 11:30:20 Yang, Sheng wrote:
> >>> From ebe4ea311305d2910dcdcff2510662da0dc2c742 Mon Sep 17 00:00:00 2001
> >>> From: Sheng Yang <sheng.yang@intel.com>
> >>> Date: Thu, 4 Sep 2008 03:11:48 +0800
> >>> Subject: [PATCH] KVM: VMX: Move private memory slot position
> >>>
> >>> PCI device assignment would map guest MMIO spaces as separate slot, so
> >>> it is possible that the device has more than 2 MMIO spaces and
> >>> overwrite current private memslot.
> >>>
> >>> The patch move private memory slot to the top of userspace visible
> >>> memory slots.
> >>
> >> Avi, these two?
> >
> > Thanks, applied both.
> >
> > Note that kvm now exports the number of slots using KVM_CAP_NR_MEMSLOTS,
> > so userspace could be made dynamic.
>
> Well, the kernel change causes the host to oops while booting Windows on
> an i386 pae host.  No idea why.

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.

(I also want to have this fix into 2.6.28, for some device would easily 
overlapped with current private memory slot)

--
regards
Yang, Sheng