6.6-stable review patch. If anyone has any objections, please let me know.
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From: Sean Christopherson seanjc@google.com
commit f402ecd7a8b6446547076f4bd24bd5d4dcc94481 upstream.
Set exit_code_hi to -1u as a temporary band-aid to fix a long-standing (effectively since KVM's inception) bug where KVM treats the exit code as a 32-bit value, when in reality it's a 64-bit value. Per the APM, offset 0x70 is a single 64-bit value:
070h 63:0 EXITCODE
And a sane reading of the error values defined in "Table C-1. SVM Intercept Codes" is that negative values use the full 64 bits:
–1 VMEXIT_INVALID Invalid guest state in VMCB. –2 VMEXIT_BUSYBUSY bit was set in the VMSA –3 VMEXIT_IDLE_REQUIREDThe sibling thread is not in an idle state -4 VMEXIT_INVALID_PMC Invalid PMC state
And that interpretation is confirmed by testing on Milan and Turin (by setting bits in CR0[63:32] to generate VMEXIT_INVALID on VMRUN).
Furthermore, Xen has treated exitcode as a 64-bit value since HVM support was adding in 2006 (see Xen commit d1bd157fbc ("Big merge the HVM full-virtualisation abstractions.")).
Cc: Jim Mattson jmattson@google.com Cc: Yosry Ahmed yosry.ahmed@linux.dev Cc: stable@vger.kernel.org Reviewed-by: Yosry Ahmed yosry.ahmed@linux.dev Link: https://patch.msgid.link/20251113225621.1688428-3-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/svm/nested.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -886,7 +886,7 @@ int nested_svm_vmrun(struct kvm_vcpu *vc if (!nested_vmcb_check_save(vcpu) || !nested_vmcb_check_controls(vcpu)) { vmcb12->control.exit_code = SVM_EXIT_ERR; - vmcb12->control.exit_code_hi = 0; + vmcb12->control.exit_code_hi = -1u; vmcb12->control.exit_info_1 = 0; vmcb12->control.exit_info_2 = 0; goto out; @@ -919,7 +919,7 @@ out_exit_err: svm->soft_int_injected = false;
svm->vmcb->control.exit_code = SVM_EXIT_ERR; - svm->vmcb->control.exit_code_hi = 0; + svm->vmcb->control.exit_code_hi = -1u; svm->vmcb->control.exit_info_1 = 0; svm->vmcb->control.exit_info_2 = 0;