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. Thanks, Tom > > Thanks, > Tom > >> >> Thanks! >> >>>> - There is a reduction of only the encryption bit in an SEV guest, so >>>> the guest can use up to a 47-bit physical address. This is why the >>>> Qemu command line sev-guest option uses a value of 1 for the >>>> "reduced-phys-bits" parameter. >>>> >>> >>> The guest statements all assume that NPT is enabled. >>> >>> Thanks, >>> Tom
