[v4,0/3] KVM: SEV-ES: Fix KVM_{GET|SET}_MSRS and LBRV handling

Message

Ravi Bangoria May 31, 2024, 4:46 a.m. UTC

Fix couple of interrelated issues:

o KVM currently allows userspace to access MSRs even after the VMSA is
  encrypted. This can result into issues if MSR update has side effects on
  VM configuration. Patch 1 fixes that by preventing KVM_{GET|SET}_MSRS
  for SEV-ES guests once VMSA is encrypted.

o As documented in APM, LBR Virtualization must be enabled for SEV-ES
  guests. However, KVM currently enables LBRV unconditionally without
  checking feature bit, which is wrong. Patch 2 prevents SEV-ES guests
  when LBRV support is missing.

o Although LBRV is enabled for SEV-ES guests, MSR_IA32_DEBUGCTLMSR was
  still intercepted. This can crash SEV-ES guest if used inadvertently.
  Patch 3 fixes it.

Patches prepared on kvm/next (6f627b425378)

v3: https://lore.kernel.org/r/[e-mail]
v3->v4:
 - Return -EINVAL instead of 0 while preventing MSR accesses post VMSA
   encryption.
 - Make 'lbrv' a global variable instead of passing it as function
   argument, this follows the pattern used by other variables.

Nikunj A Dadhania (1):
  KVM: SEV-ES: Prevent MSR access post VMSA encryption

Ravi Bangoria (2):
  KVM: SEV-ES: Disallow SEV-ES guests when X86_FEATURE_LBRV is absent
  KVM: SEV-ES: Fix LBRV code

 arch/x86/kvm/svm/sev.c | 19 ++++++++++++++-----
 arch/x86/kvm/svm/svm.c | 42 ++++++++++++++++++++++++++++++++----------
 arch/x86/kvm/svm/svm.h |  4 +++-
 3 files changed, 49 insertions(+), 16 deletions(-)

Comments

Paolo Bonzini June 3, 2024, 5:05 p.m. UTC | #1

Queued, thanks.

Paolo