Re: [PATCH v4 00/28] KVM: combined patchset for MBEC/GMET support

Paolo Bonzini
2026-04-29T13:12:48Z

On 4/29/26 15:05, David Riley wrote:
> Windows Guest:
> After the initial installation and verification I enabled
> Virtualization-Based Security (VBS) and Hypervisor-Protected Code
> Integrity (HVCI).
>
> I set the following in the Group Policy Editor (DeviceGuard):
> * Select Platform Security Level: Secure Boot
> * Virtualization Based Protection of Code Integrity: Enabled without
>    lock
> * Require UEFI Memory Attributes Table: Checked
>
> I tried to launch the Windows Guest with these QEMU CPU options:
> -cpu 'host,+kvm_pv_eoi,+kvm_pv_unhalt,level=30'
>
> These flags worked with the last patch series (v3) without any issues
> [2][3].
>
> I observed the following:
> The guest now never actually boots into Windows. It gets stuck before
> that and therefore does not even enter Windows Recovery.

Interesting, I'll see if I can reproduce.

> I found the following log in the journal:
> Apr 29 13:44:55 jura2 kernel: kvm_amd: kvm [29717]: vcpu0, guest rIP:
> 0xfffff83560f3b225 Unhandled WRMSR(0xc0010115) = 0x0
>
> the same messages also appeared in dmesg:
> [ 1910.476609] kvm_amd: kvm [8755]: vcpu0, guest rIP:
> 0xfffff851f793b225 Unhandled WRMSR(0xc0010115) = 0x0

This is harmless.

> I also did a trace using `trace-cmd record -e kvm` and observed that
> the cpu seems to be stuck in a infinite loop. Snippet of the output:
>
>        CPU 0/KVM-29834 [020] .....  8801.135700: kvm_page_fault:
>  vcpu 0 rip 0xfffff83560f8f6a0 address 0x00000001011e9f80 error_code
> 0x200000007
>        CPU 0/KVM-29834 [020] d..1.  8801.135701: kvm_entry:      vcpu 0
> rip 0xfffff83560f8f6a0
>        CPU 0/KVM-29834 [020] d..1.  8801.135702: kvm_exit:      reason
> EXIT_NPF rip 0xfffff83560f8f6a0 info 200000007 1011e9f80
>        CPU 0/KVM-29834 [020] .....  8801.135702: kvm_nested_vmexit:
> <CANT FIND FIELD rip>vcpu 0 reason npf rip 0xfffff83560f8f6a0 info1
> 0x0000000200000007 info2 0x00000001011e9f80 intr_info 0x00000000
> error_code 0x00000000 requests 0x0000000000000000
>        CPU 0/KVM-29834 [020] .....  8801.135703: kvm_page_fault:
>  vcpu 0 rip 0xfffff83560f8f6a0 address 0x00000001011e9f80 error_code
> 0x200000007
>        CPU 0/KVM-29834 [020] d..1.  8801.135704: kvm_entry:      vcpu 0
> rip 0xfffff83560f8f6a0
>        CPU 0/KVM-29834 [020] d..1.  8801.135705: kvm_exit:      reason
> EXIT_NPF rip 0xfffff83560f8f6a0 info 200000007 1011e9f80
>        CPU 0/KVM-29834 [020] .....  8801.135705: kvm_nested_vmexit:
> <CANT FIND FIELD rip>vcpu 0 reason npf rip 0xfffff83560f8f6a0 info1
> 0x0000000200000007 info2 0x00000001011e9f80 intr_info 0x00000000
> error_code 0x00000000 requests 0x0000000000000000
>
> Could this be related to the new patch 24?

I wouldn't think so, but I might very well be wrong. You could try
reverting it.

Paolo

> Are there certain flags or enhancements I could try?
>
> Please let me know if you need some additional debug output.
>
> Best regards,
> David
>
> [0] https://gitlab.com/qemu-project/qemu/-/
> commit/746a823a17f25393cc8c0cd1257f6dcef757bc09
> [1] https://learn.microsoft.com/en-us/windows/security/hardware-
> security/enable-virtualization-based-protection-of-code-integrity?
> tabs=security
> [2] https://lore.kernel.org/kvm/20260408154217.458420-1-
> pbonzini@redhat.com/
> [3] https://lore.kernel.org/kvm/c91391f4-57b8-4bad-
> aba8-2c47c285ab27@proxmox.com/
>
> On 4/28/26 1:33 PM, Paolo Bonzini wrote:
>> I will send you to v3 (https://lore.kernel.org/
>> kvm/20260408154217.458420-1-pbonzini@redhat.com/)
>> for the description of the series, and leave a short list of changes:
>>
>> - patch 15: clear enable_mbec = 0 if enable_ept == 0
>> - patches 23-27: adjust for rename of nested_ctl to misc_ctl
>> - patch 24: new
>> - patch 27: disable svm_get_cpl for SEV-ES/SEV-SNP
>> - patch 28: fix commit message reference to __nested_svm_check_controls
>>
>> (patch 24 is the only major bugfix).
>>
>> Thanks,
>>
>> Paolo
>>
>> Jon Kohler (5):
>>    KVM: TDX/VMX: rework EPT_VIOLATION_EXEC_FOR_RING3_LIN into PROT_MASK
>>    KVM: x86/mmu: remove SPTE_PERM_MASK
>>    KVM: x86/mmu: free up bit 10 of PTEs in preparation for MBEC
>>    KVM: nVMX: advertise MBEC to nested guests
>>    KVM: nVMX: allow MBEC with EVMCS
>>
>> Paolo Bonzini (23):
>>    KVM: x86/mmu: shuffle high bits of SPTEs in preparation for MBEC
>>    KVM: x86/mmu: remove SPTE_EPT_*
>>    KVM: x86/mmu: merge make_spte_{non,}executable
>>    KVM: x86/mmu: rename and clarify BYTE_MASK
>>    KVM: x86/mmu: introduce ACC_READ_MASK
>>    KVM: x86/mmu: separate more EPT/non-EPT permission_fault()
>>    KVM: x86/mmu: pass PFERR_GUEST_PAGE/FINAL_MASK to kvm_translate_gpa
>>    KVM: x86/mmu: pass pte_access for final nGPA->GPA walk
>>    KVM: x86: make translate_nested_gpa vendor-specific
>>    KVM: x86/mmu: split XS/XU bits for EPT
>>    KVM: x86/mmu: move cr4_smep to base role
>>    KVM: VMX: enable use of MBEC
>>    KVM: nVMX: pass advanced EPT violation vmexit info to guest
>>    KVM: nVMX: pass PFERR_USER_MASK to MMU on EPT violations
>>    KVM: x86/mmu: add support for MBEC to EPT page table walks
>>    KVM: x86/mmu: propagate access mask from root pages down
>>    KVM: x86/mmu: introduce cpu_role bit for availability of PFEC.I/D
>>    KVM: SVM: add GMET bit definitions
>>    KVM: x86/mmu: set CR0.WP=1 for shadow NPT MMU
>>    KVM: x86/mmu: add support for GMET to NPT page table walks
>>    KVM: SVM: enable GMET and set it in MMU role
>>    KVM: SVM: work around errata 1218
>>    KVM: nSVM: enable GMET for guests
>>
>>   Documentation/virt/kvm/x86/mmu.rst |  10 +-
>>   arch/x86/include/asm/cpufeatures.h |   1 +
>>   arch/x86/include/asm/kvm-x86-ops.h |   1 +
>>   arch/x86/include/asm/kvm_host.h    |  48 ++++++---
>>   arch/x86/include/asm/svm.h         |   1 +
>>   arch/x86/include/asm/vmx.h         |  14 ++-
>>   arch/x86/kvm/hyperv.c              |   4 +-
>>   arch/x86/kvm/mmu.h                 |  30 ++++--
>>   arch/x86/kvm/mmu/mmu.c             | 168 ++++++++++++++++++++---------
>>   arch/x86/kvm/mmu/mmutrace.h        |  19 ++--
>>   arch/x86/kvm/mmu/paging_tmpl.h     |  73 ++++++++-----
>>   arch/x86/kvm/mmu/spte.c            |  74 +++++++------
>>   arch/x86/kvm/mmu/spte.h            |  70 ++++++------
>>   arch/x86/kvm/mmu/tdp_mmu.c         |   6 +-
>>   arch/x86/kvm/svm/nested.c          |  37 ++++++-
>>   arch/x86/kvm/svm/svm.c             |  31 ++++++
>>   arch/x86/kvm/svm/svm.h             |   1 +
>>   arch/x86/kvm/vmx/capabilities.h    |  12 ++-
>>   arch/x86/kvm/vmx/common.h          |  20 ++--
>>   arch/x86/kvm/vmx/hyperv_evmcs.h    |   1 +
>>   arch/x86/kvm/vmx/main.c            |   9 ++
>>   arch/x86/kvm/vmx/nested.c          |  46 +++++++-
>>   arch/x86/kvm/vmx/tdx.c             |   2 +-
>>   arch/x86/kvm/vmx/vmx.c             |  27 ++++-
>>   arch/x86/kvm/vmx/vmx.h             |   1 +
>>   arch/x86/kvm/vmx/x86_ops.h         |   1 +
>>   arch/x86/kvm/x86.c                 |  18 +---
>>   27 files changed, 505 insertions(+), 220 deletions(-)
>>
>