[Hygon][6.6][KVM] SVM: Fix SPEC_CTRL intercept · Pull Request !748 · OpenCloudOS/OpenCloudOS-Kernel

This bug is observable with kvm-unit-tests. On a V_SPEC_CTRL-capable host (e.g. AMD Zen2+, Hygon Gen4), 
./run_test.sh msr64 reports:
      FAIL: Expected #GP on RDMSR(SPEC_CTRL), got vector 0
      FAIL: Expected #GP on WRMSR(SPEC_CTRL, 0x0), got vector 0
  
When the host supports Virtual SPEC_CTRL (V_SPEC_CTRL), init_vmcb()
unconditionally disables interception of MSR_IA32_SPEC_CTRL, i.e. passes
the MSR through to the guest, without regard for the guest's CPUID. On
such hardware a guest RDMSR/WRMSR of IA32_SPEC_CTRL is serviced directly
from the VMCB save area and never exits to KVM, so a guest whose CPUID
advertises none of SPEC_CTRL, AMD_IBRS, AMD_STIBP or AMD_SSBD can freely
read and write the MSR instead of taking the #GP it would see on bare
metal.
    
svm_get_msr()/svm_set_msr() already reject the access for such a guest.
They return 1 (and KVM injects #GP) when !guest_has_spec_ctrl_msr(), but
the passthrough bypasses those handlers entirely. The passthrough is also
programmed in init_vmcb(), before the guest CPUID has been configured, so
it cannot take the guest's feature set into account in the first place.

Drop the unconditional passthrough from init_vmcb() and instead program
the SPEC_CTRL intercept from svm_vcpu_after_set_cpuid(), gated on
guest_has_spec_ctrl_msr(). SPEC_CTRL now stays intercepted for guests
without the MSR (so KVM injects #GP) and is passed through only once the
guest's CPUID shows it has the MSR. The on-demand passthrough that
svm_set_msr() performs after the guest's first legitimate write is
unaffected.
    
This is the SPEC_CTRL portion of the upstream MSR-interception rework
merged in v6.17, which moved the decision into svm_recalc_msr_intercepts():
Commit 160f143cc1317a599ef44c8d35a1328f2dd7a14d
    
It is applied here as a minimal fix against the v6.6 set_msr_interception()
API rather than backporting the full series.

类型	指派人员	状态
审查	chinaljp030 刘诗	已完成 (0/0人)
测试	chinaljp030 刘诗	已完成 (0/0人)

GVPOpenCloudOS/OpenCloudOS-Kernel

搜索帮助

GVP OpenCloudOS/OpenCloudOS-Kernel