On 1/26/21 5:39 AM, Paolo Bonzini wrote:
On 26/01/21 09:18, Wei Huang wrote:
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(-)
Queued, thanks.
Thanks. BTW because we use kvm_cpu_cap_set() in svm_set_cpu_caps(). This
will be reflected into the CPUID received by QEMU. QEMU needs a one-line
patch to declare the new feature. I will send it out this morning.
-Wei
Paolo
