[PATCH 2/2] KVM: PPC: Book3E: Get vcpu's last instruction for emulation

[Alexander Graf]

On 10.07.2013, at 02:12, Scott Wood wrote:

> On 07/09/2013 04:45:10 PM, Alexander Graf wrote:
>> On 28.06.2013, at 11:20, Mihai Caraman wrote:
>> > +	/* Get page size */
>> > +	if (MAS0_GET_TLBSEL(mfspr(SPRN_MAS0)) == 0)
>> > +		psize_shift = PAGE_SHIFT;
>> > +	else
>> > +		psize_shift = MAS1_GET_TSIZE(mas1) + 10;
>> > +
>> > +	mas7_mas3 = (((u64) mfspr(SPRN_MAS7)) << 32) |
>> > +		    mfspr(SPRN_MAS3);
>> > +	addr = (mas7_mas3 & (~0ULL << psize_shift)) |
>> > +	       (geaddr & ((1ULL << psize_shift) - 1ULL));
>> > +
>> > +	/* Map a page and get guest's instruction */
>> > +	page = pfn_to_page(addr >> PAGE_SHIFT);
>> While looking at this I just realized that you're missing a check here. What if our IP is in some PCI BAR? Or can't we execute from those?
> 
> We at least need to check pfn_valid() first.  That'll just keep us from accessing a bad pointer in the host kernel, though -- it won't make the emulation actually work.  If we need that, we'll probably need to create a temporary TLB entry manually.

ioremap()?

However, if we were walking the guest TLB cache instead we would get a guest physical address which we can always resolve to a host virtual address.

I'm not sure how important that whole use case is though. Maybe we should just error out to the guest for now.


Alex