Re: [PATCH v4 00/28] KVM: combined patchset for MBEC/GMET support
From: Paolo Bonzini
Date: Wed Apr 29 2026 - 09:20:08 EST
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@xxxxxxxxxx/
[3] https://lore.kernel.org/kvm/c91391f4-57b8-4bad- aba8-2c47c285ab27@xxxxxxxxxxx/
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@xxxxxxxxxx/)
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(-)