On 04/10/19 21:06, Edgecombe, Rick P wrote: > The reasoning was that it seems like KVM leaves it to userspace to control the > physical address space layout since userspace decides the supported physical > address bits and lays out memory in the physical address space. So duplication > with XO memslots was an attempt was to keep the logic around that together. > > I'll take another look at doing it this way though. I think userspace may > still > need to adjust the MAXPHYADDR and be aware it can't layout memory in the XO > range.
Right, you would have to use KVM_ENABLE_CAP passing the desired X bit (which must be < MAXPHYADDR) as the argument. Userspace needs to know that it must then make MAXPHYADDR in the guest CPUID equal to the argument. When the MSR is written to 1, bit "MAXPHYADDR-1" in the page table entries becomes an XO bit. Paolo
