On 6/24/21 5:15 PM, Sean Christopherson wrote: > On Thu, Jun 24, 2021, Tom Lendacky wrote: >> On 6/24/21 12:39 PM, Tom Lendacky wrote: >>> >>> >>> On 6/24/21 12:31 PM, Sean Christopherson wrote: >>>> On Thu, Jun 24, 2021, Tom Lendacky wrote: >>>>>> >>>>>> Here's an explanation of the physical address reduction for bare-metal and >>>>>> guest. >>>>>> >>>>>> With MSR 0xC001_0010[SMEE] = 0: >>>>>> No reduction in host or guest max physical address. >>>>>> >>>>>> With MSR 0xC001_0010[SMEE] = 1: >>>>>> - Reduction in the host is enumerated by CPUID 0x8000_001F_EBX[11:6], >>>>>> regardless of whether SME is enabled in the host or not. So, for example >>>>>> on EPYC generation 2 (Rome) you would see a reduction from 48 to 43. >>>>>> - There is no reduction in physical address in a legacy guest (non-SEV >>>>>> guest), so the guest can use a 48-bit physical address >>>> >>>> So the behavior I'm seeing is either a CPU bug or user error. Can you verify >>>> the unexpected #PF behavior to make sure I'm not doing something stupid? >>> >>> Yeah, I saw that in patch #3. Let me see what I can find out. I could just >>> be wrong on that myself - it wouldn't be the first time. >> >> From patch #3: >> SVM: KVM: CPU #PF @ rip = 0x409ca4, cr2 = 0xc0000000, pfec = 0xb >> KVM: guest PTE = 0x181023 @ GPA = 0x180000, level = 4 >> KVM: guest PTE = 0x186023 @ GPA = 0x181000, level = 3 >> KVM: guest PTE = 0x187023 @ GPA = 0x186000, level = 2 >> KVM: guest PTE = 0xffffbffff003 @ GPA = 0x187000, level = 1 >> SVM: KVM: GPA = 0x7fffbffff000 >> >> I think you may be hitting a special HT region that is at the top 12GB of >> the 48-bit memory range and is reserved, even for GPAs. Can you somehow >> get the test to use an address below 0xfffd_0000_0000? That would show >> that bit 47 is valid for the legacy guest while staying out of the HT region. > > I can make that happen. > > I assume "HT" is HyperTransport? Yep. Thanks, Tom >
