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  1. 14 Jul, 2021 7 commits
    • Sean Christopherson's avatar
      KVM: SVM: Revert clearing of C-bit on GPA in #NPF handler · 76ff371b
      Sean Christopherson authored 
      Don't clear the C-bit in the #NPF handler, as it is a legal GPA bit for
non-SEV guests, and for SEV guests the C-bit is dropped before the GPA
hits the NPT in hardware.  Clearing the bit for non-SEV guests causes KVM
to mishandle #NPFs with that collide with the host's C-bit.

Although the APM doesn't explicitly state that the C-bit is not reserved
for non-SEV, Tom Lendacky confirmed that the following snippet about the
effective reduction due to the C-bit does indeed apply only to SEV guests.

  Note that because guest physical addresses are always translated
  through the nested page tables, the size of the guest physical address
  space is not impacted by any physical address space reduction indicated
  in CPUID 8000_001F[EBX]. If the C-bit is a physical address bit however,
  the guest physical address space is effectively reduced by 1 bit.

And for SEV guests, the APM clearly states that the bit is dropped before
walking the nested page tables.

  If the C-bit is an address bit, this bit is masked from the guest
  physical address when it is translated through the nested page tables.
  Consequently, the hypervisor does not need to be aware of which pages
  the guest has chosen to mark private.

Note, the bogus C-bit clearing was removed from legacy #PF handler in
commit 6d1b867d ("KVM: SVM: Don't strip the C-bit from CR2 on #PF
interception").

Fixes: 0ede79e1 ("KVM: SVM: Clear C-bit from the page fault address")
Cc: Peter Gonda <pgonda@google.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210625020354.431829-3-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      76ff371b
    • Sean Christopherson's avatar
      KVM: x86/mmu: Do not apply HPA (memory encryption) mask to GPAs · fc9bf2e0
      Sean Christopherson authored 
      Ignore "dynamic" host adjustments to the physical address mask when
generating the masks for guest PTEs, i.e. the guest PA masks.  The host
physical address space and guest physical address space are two different
beasts, e.g. even though SEV's C-bit is the same bit location for both
host and guest, disabling SME in the host (which clears shadow_me_mask)
does not affect the guest PTE->GPA "translation".

For non-SEV guests, not dropping bits is the correct behavior.  Assuming
KVM and userspace correctly enumerate/configure guest MAXPHYADDR, bits
that are lost as collateral damage from memory encryption are treated as
reserved bits, i.e. KVM will never get to the point where it attempts to
generate a gfn using the affected bits.  And if userspace wants to create
a bogus vCPU, then userspace gets to deal with the fallout of hardware
doing odd things with bad GPAs.

For SEV guests, not dropping the C-bit is technically wrong, but it's a
moot point because KVM can't read SEV guest's page tables in any case
since they're always encrypted.  Not to mention that the current KVM code
is also broken since sme_me_mask does not have to be non-zero for SEV to
be supported by KVM.  The proper fix would be to teach all of KVM to
correctly handle guest private memory, but that's a task for the future.

Fixes: d0ec49d4 ("kvm/x86/svm: Support Secure Memory Encryption within KVM")
Cc: stable@vger.kernel.org
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210623230552.4027702-5-seanjc@google.com>
[Use a new header instead of adding header guards to paging_tmpl.h. - Paolo]
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      fc9bf2e0
    • Sean Christopherson's avatar
      KVM: x86: Use kernel's x86_phys_bits to handle reduced MAXPHYADDR · e39f00f6
      Sean Christopherson authored 
      Use boot_cpu_data.x86_phys_bits instead of the raw CPUID information to
enumerate the MAXPHYADDR for KVM guests when TDP is disabled (the guest
version is only relevant to NPT/TDP).

When using shadow paging, any reductions to the host's MAXPHYADDR apply
to KVM and its guests as well, i.e. using the raw CPUID info will cause
KVM to misreport the number of PA bits available to the guest.

Unconditionally zero out the "Physical Address bit reduction" entry.
For !TDP, the adjustment is already done, and for TDP enumerating the
host's reduction is wrong as the reduction does not apply to GPAs.

Fixes: 9af9b940 ("x86/cpu/AMD: Handle SME reduction in physical address size")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210623230552.4027702-3-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      e39f00f6
    • Sean Christopherson's avatar
      KVM: x86: Use guest MAXPHYADDR from CPUID.0x8000_0008 iff TDP is enabled · 4bf48e3c
      Sean Christopherson authored 
      Ignore the guest MAXPHYADDR reported by CPUID.0x8000_0008 if TDP, i.e.
NPT, is disabled, and instead use the host's MAXPHYADDR.  Per AMD'S APM:

  Maximum guest physical address size in bits. This number applies only
  to guests using nested paging. When this field is zero, refer to the
  PhysAddrSize field for the maximum guest physical address size.

Fixes: 24c82e57 ("KVM: Sanitize cpuid")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210623230552.4027702-2-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      4bf48e3c
    • Sean Christopherson's avatar
      Revert "KVM: x86: WARN and reject loading KVM if NX is supported but not enabled" · f0414b07
      Sean Christopherson authored 
      Let KVM load if EFER.NX=0 even if NX is supported, the analysis and
testing (or lack thereof) for the non-PAE host case was garbage.

If the kernel won't be using PAE paging, .Ldefault_entry in head_32.S
skips over the entire EFER sequence.  Hopefully that can be changed in
the future to allow KVM to require EFER.NX, but the motivation behind
KVM's requirement isn't yet merged.  Reverting and revisiting the mess
at a later date is by far the safest approach.

This reverts commit 8bbed95d.

Fixes: 8bbed95d ("KVM: x86: WARN and reject loading KVM if NX is supported but not enabled")
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210625001853.318148-1-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      f0414b07
    • Marc Zyngier's avatar
      KVM: selftests: x86: Address missing vm_install_exception_handler conversions · f8f0edab
      Marc Zyngier authored 
      Commit b78f4a59 ("KVM: selftests: Rename vm_handle_exception")
raced with a couple of new x86 tests, missing two vm_handle_exception
to vm_install_exception_handler conversions.

Help the two broken tests to catch up with the new world.

Cc: Andrew Jones <drjones@redhat.com>
CC: Ricardo Koller <ricarkol@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Message-Id: <20210701071928.2971053-1-maz@kernel.org>
Reviewed-by: default avatarAndrew Jones <drjones@redhat.com>
Reviewed-by: default avatarRicardo Koller <ricarkol@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      f8f0edab
    • Paolo Bonzini's avatar
      Merge tag 'kvm-s390-master-5.14-1' of... · f3cf8007
      Paolo Bonzini authored 
      Merge tag 'kvm-s390-master-5.14-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into HEAD

KVM: selftests: Fixes

- provide memory model for  IBM z196 and zEC12
- do not require 64GB of memory
      f3cf8007
  3. 06 Jul, 2021 2 commits
  5. 25 Jun, 2021 3 commits
  7. 24 Jun, 2021 28 commits
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