[Bug 219618] New: qemu cannot not start with -cpu hypervisor=off parameter

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=219618

            Bug ID: 219618
           Summary: qemu cannot not start with -cpu hypervisor=off
                    parameter
           Product: Virtualization
           Version: unspecified
          Hardware: AMD
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: kvm
          Assignee: virtualization_kvm@kernel-bugs.osdl.org
          Reporter: athul.krishna.kr@protonmail.com
        Regression: No

Device: Asus Zephyrus GA402RJ
CPU: Ryzen 7 6800HS
Kernel: 6.13.0-rc3-g800f6e23e031

Problem:
After kernel 6.12, my qemu windows 11 vm won't start when using '-cpu
hypervisor=off'.

Commit:
74a0e79df68a8042fb84fd7207e57b70722cf825 is the first bad commit
commit 74a0e79df68a8042fb84fd7207e57b70722cf825
Author: Sean Christopherson <seanjc@google.com>
Date:   Fri Aug 2 11:19:26 2024 -0700

    KVM: SVM: Disallow guest from changing userspace's MSR_AMD64_DE_CFG value

    Inject a #GP if the guest attempts to change MSR_AMD64_DE_CFG from its
    *current* value, not if the guest attempts to write a value other than
    KVM's set of supported bits.  As per the comment and the changelog of the
    original code, the intent is to effectively make MSR_AMD64_DE_CFG read-
    only for the guest.

    Opportunistically use a more conventional equality check instead of an
    exclusive-OR check to detect attempts to change bits.

    Fixes: d1d93fa90f1a ("KVM: SVM: Add MSR-based feature support for
serializing LFENCE")
    Cc: Tom Lendacky <thomas.lendacky@amd.com>
    Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
    Link: https://lore.kernel.org/r/20240802181935.292540-2-seanjc@google.com
    Signed-off-by: Sean Christopherson <seanjc@google.com>

 arch/x86/kvm/svm/svm.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

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