[PATCH v3 0/4] Handle #GP for SVM execution instructions

[Wei Huang <wei.huang2@amd.com>]

While running SVM related instructions (VMRUN/VMSAVE/VMLOAD), some AMD
CPUs check EAX against reserved memory regions (e.g. SMM memory on host)
before checking VMCB's instruction intercept. If EAX falls into such
memory areas, #GP is triggered before #VMEXIT. This causes unexpected #GP
under nested virtualization. To solve this problem, this patchset makes
KVM trap #GP and emulate these SVM instuctions accordingly.

Also newer AMD CPUs will change this behavior by triggering #VMEXIT
before #GP. This change is indicated by CPUID_0x8000000A_EDX[28]. Under
this circumstance, #GP interception is not required. This patchset supports
the new feature.

This patchset has been verified with vmrun_errata_test and vmware_backdoor
tests of kvm_unit_test on the following configs. Also it was verified that
vmware_backdoor can be turned on under nested on nested.
  * Current CPU: nested, nested on nested
  * New CPU with X86_FEATURE_SVME_ADDR_CHK: nested, nested on nested

v2->v3:
  * Change the decode function name to x86_decode_emulated_instruction()
  * Add a new variable, svm_gp_erratum_intercept, to control interception
  * Turn on VM's X86_FEATURE_SVME_ADDR_CHK feature in svm_set_cpu_caps()
  * Fix instruction emulation for vmware_backdoor under nested-on-nested
  * Minor comment fixes

v1->v2:
  * Factor out instruction decode for sharing
  * Re-org gp_interception() handling for both #GP and vmware_backdoor
  * Use kvm_cpu_cap for X86_FEATURE_SVME_ADDR_CHK feature support
  * Add nested on nested support

Thanks,
-Wei

Wei Huang (4):
  KVM: x86: Factor out x86 instruction emulation with decoding
  KVM: SVM: Add emulation support for #GP triggered by SVM instructions
  KVM: SVM: Add support for SVM instruction address check change
  KVM: SVM: Support #GP handling for the case of nested on nested

 arch/x86/include/asm/cpufeatures.h |   1 +
 arch/x86/kvm/svm/svm.c             | 128 +++++++++++++++++++++++++----
 arch/x86/kvm/x86.c                 |  62 ++++++++------
 arch/x86/kvm/x86.h                 |   2 +
 4 files changed, 152 insertions(+), 41 deletions(-)

-- 
2.27.0