From f402ecd7a8b6446547076f4bd24bd5d4dcc94481 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 13 Nov 2025 14:56:14 -0800 Subject: [PATCH] KVM: nSVM: Set exit_code_hi to -1 when synthesizing SVM_EXIT_ERR (failed VMRUN) MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Cc: Yosry Ahmed Cc: stable@vger.kernel.org Reviewed-by: Yosry Ahmed Link: https://patch.msgid.link/20251113225621.1688428-3-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/svm/nested.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index da6e80b3ac35..143a0ef02b03 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -983,7 +983,7 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu) 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; @@ -1016,7 +1016,7 @@ 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; -- 2.47.3