From nobody Thu Apr 2 06:27:04 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 49BB7237707; Tue, 3 Mar 2026 00:34:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772498073; cv=none; b=T6hHvc1Y5bCe/f7HXxj9E3Gn/+moL5btPGsu8bkJ1qApCylUOr4Ug9OIkaKaJz9NDd/5hdjVBk7JirtfJkD/F+W8ZxSl6wo/eA/erQRp6OIqjE2lKHgxxtsRPhyF9i2r1JLeENDMkR+HCm287st+EG8+nSCR0dILFQCh9Gi/L08= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772498073; c=relaxed/simple; bh=Ppt/tEFVP57TI65aOpNIHi11mVfA2f/wK0mP+p0lMVI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uP3hS4vfaSZMOvcird3QSbpXgb7AN3ARsQl0Hbae0s67Tt414vsFMO28FLAZ0wQHhC1zfeh9W96QYhs2JUheQShlDxdbXM6GKPIneLPCehdS6UdOv1LzLGwtjq0EnHV53OIZL3U1J/HaUdSHjjSNdBiJjV6VO7FfXgD7CKMir9s= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NVNTax0A; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NVNTax0A" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DF537C4AF09; Tue, 3 Mar 2026 00:34:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772498073; bh=Ppt/tEFVP57TI65aOpNIHi11mVfA2f/wK0mP+p0lMVI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NVNTax0A82oCelbkZGDWberlI1Qg3Z12IpJrCHhTGUGezvr1bOfQJ03MObAtdzmls hqVrslLkGFdfbIkKk7SCGOVN4MJq1C4bnSX4pxqF2VY7cCJsZYUP7GwaU4nn6rj0rI lvtU6l/znwqui9lsOLZ3GpO3We35OyYCN2+dc3HtQM9Eoq3Mj6PsVgh5HiAcAHb5nT SzjyU7z2QTe/ap+bEP1DRik2pEnMnmUWLwvnyhnNG+BW9smyrCdl+8ZBe8o23iTm6A Mkcy3th7AIjobIrhIJqOBwm3ATCNuzMQTATUjV/0QJO6+8OtiSNOC7iLIPm9foN5nX TW/4tJtQjYVig== From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Subject: [PATCH v7 04/26] KVM: selftests: Add a test for LBR save/restore (ft. nested) Date: Tue, 3 Mar 2026 00:33:58 +0000 Message-ID: <20260303003421.2185681-5-yosry@kernel.org> X-Mailer: git-send-email 2.53.0.473.g4a7958ca14-goog In-Reply-To: <20260303003421.2185681-1-yosry@kernel.org> References: <20260303003421.2185681-1-yosry@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a selftest exercising save/restore with usage of LBRs in both L1 and L2, and making sure all LBRs remain intact. Signed-off-by: Yosry Ahmed --- tools/testing/selftests/kvm/Makefile.kvm | 1 + .../selftests/kvm/include/x86/processor.h | 5 + .../selftests/kvm/x86/svm_lbr_nested_state.c | 145 ++++++++++++++++++ 3 files changed, 151 insertions(+) create mode 100644 tools/testing/selftests/kvm/x86/svm_lbr_nested_state.c diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selft= ests/kvm/Makefile.kvm index fdec90e854671..36b48e766e499 100644 --- a/tools/testing/selftests/kvm/Makefile.kvm +++ b/tools/testing/selftests/kvm/Makefile.kvm @@ -112,6 +112,7 @@ TEST_GEN_PROGS_x86 +=3D x86/svm_vmcall_test TEST_GEN_PROGS_x86 +=3D x86/svm_int_ctl_test TEST_GEN_PROGS_x86 +=3D x86/svm_nested_shutdown_test TEST_GEN_PROGS_x86 +=3D x86/svm_nested_soft_inject_test +TEST_GEN_PROGS_x86 +=3D x86/svm_lbr_nested_state TEST_GEN_PROGS_x86 +=3D x86/tsc_scaling_sync TEST_GEN_PROGS_x86 +=3D x86/sync_regs_test TEST_GEN_PROGS_x86 +=3D x86/ucna_injection_test diff --git a/tools/testing/selftests/kvm/include/x86/processor.h b/tools/te= sting/selftests/kvm/include/x86/processor.h index 4ebae4269e681..db0171935197d 100644 --- a/tools/testing/selftests/kvm/include/x86/processor.h +++ b/tools/testing/selftests/kvm/include/x86/processor.h @@ -1360,6 +1360,11 @@ static inline bool kvm_is_ignore_msrs(void) return get_kvm_param_bool("ignore_msrs"); } =20 +static inline bool kvm_is_lbrv_enabled(void) +{ + return !!get_kvm_amd_param_integer("lbrv"); +} + uint64_t *vm_get_pte(struct kvm_vm *vm, uint64_t vaddr); =20 uint64_t kvm_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2, diff --git a/tools/testing/selftests/kvm/x86/svm_lbr_nested_state.c b/tools= /testing/selftests/kvm/x86/svm_lbr_nested_state.c new file mode 100644 index 0000000000000..bf16abb1152e0 --- /dev/null +++ b/tools/testing/selftests/kvm/x86/svm_lbr_nested_state.c @@ -0,0 +1,145 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2026, Google, Inc. + */ + +#include "test_util.h" +#include "kvm_util.h" +#include "processor.h" +#include "svm_util.h" + + +#define L2_GUEST_STACK_SIZE 64 + +#define DO_BRANCH() do { asm volatile("jmp 1f\n 1: nop"); } while (0) + +struct lbr_branch { + u64 from, to; +}; + +volatile struct lbr_branch l2_branch; + +#define RECORD_AND_CHECK_BRANCH(b) \ +do { \ + wrmsr(MSR_IA32_DEBUGCTLMSR, DEBUGCTLMSR_LBR); \ + DO_BRANCH(); \ + (b)->from =3D rdmsr(MSR_IA32_LASTBRANCHFROMIP); \ + (b)->to =3D rdmsr(MSR_IA32_LASTBRANCHTOIP); \ + /* Disable LBR right after to avoid overriding the IPs */ \ + wrmsr(MSR_IA32_DEBUGCTLMSR, 0); \ + \ + GUEST_ASSERT_NE((b)->from, 0); \ + GUEST_ASSERT_NE((b)->to, 0); \ +} while (0) + +#define CHECK_BRANCH_MSRS(b) \ +do { \ + GUEST_ASSERT_EQ((b)->from, rdmsr(MSR_IA32_LASTBRANCHFROMIP)); \ + GUEST_ASSERT_EQ((b)->to, rdmsr(MSR_IA32_LASTBRANCHTOIP)); \ +} while (0) + +#define CHECK_BRANCH_VMCB(b, vmcb) \ +do { \ + GUEST_ASSERT_EQ((b)->from, vmcb->save.br_from); \ + GUEST_ASSERT_EQ((b)->to, vmcb->save.br_to); \ +} while (0) + +static void l2_guest_code(struct svm_test_data *svm) +{ + /* Record a branch, trigger save/restore, and make sure LBRs are intact */ + RECORD_AND_CHECK_BRANCH(&l2_branch); + GUEST_SYNC(true); + CHECK_BRANCH_MSRS(&l2_branch); + vmmcall(); +} + +static void l1_guest_code(struct svm_test_data *svm, bool nested_lbrv) +{ + unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE]; + struct vmcb *vmcb =3D svm->vmcb; + struct lbr_branch l1_branch; + + /* Record a branch, trigger save/restore, and make sure LBRs are intact */ + RECORD_AND_CHECK_BRANCH(&l1_branch); + GUEST_SYNC(true); + CHECK_BRANCH_MSRS(&l1_branch); + + /* Run L2, which will also do the same */ + generic_svm_setup(svm, l2_guest_code, + &l2_guest_stack[L2_GUEST_STACK_SIZE]); + + if (nested_lbrv) + vmcb->control.virt_ext =3D LBR_CTL_ENABLE_MASK; + else + vmcb->control.virt_ext &=3D ~LBR_CTL_ENABLE_MASK; + + run_guest(vmcb, svm->vmcb_gpa); + GUEST_ASSERT(svm->vmcb->control.exit_code =3D=3D SVM_EXIT_VMMCALL); + + /* Trigger save/restore one more time before checking, just for kicks */ + GUEST_SYNC(true); + + /* + * If LBR_CTL_ENABLE is set, L1 and L2 should have separate LBR MSRs, so + * expect L1's LBRs to remain intact and L2 LBRs to be in the VMCB. + * Otherwise, the MSRs are shared between L1 & L2 so expect L2's LBRs. + */ + if (nested_lbrv) { + CHECK_BRANCH_MSRS(&l1_branch); + CHECK_BRANCH_VMCB(&l2_branch, vmcb); + } else { + CHECK_BRANCH_MSRS(&l2_branch); + } + GUEST_DONE(); +} + +void test_lbrv_nested_state(bool nested_lbrv) +{ + struct kvm_x86_state *state =3D NULL; + struct kvm_vcpu *vcpu; + vm_vaddr_t svm_gva; + struct kvm_vm *vm; + struct ucall uc; + + pr_info("Testing with nested LBRV %s\n", nested_lbrv ? "enabled" : "disab= led"); + + vm =3D vm_create_with_one_vcpu(&vcpu, l1_guest_code); + vcpu_alloc_svm(vm, &svm_gva); + vcpu_args_set(vcpu, 2, svm_gva, nested_lbrv); + + for (;;) { + vcpu_run(vcpu); + TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO); + switch (get_ucall(vcpu, &uc)) { + case UCALL_SYNC: + /* Save the vCPU state and restore it in a new VM on sync */ + pr_info("Guest triggered save/restore.\n"); + state =3D vcpu_save_state(vcpu); + kvm_vm_release(vm); + vcpu =3D vm_recreate_with_one_vcpu(vm); + vcpu_load_state(vcpu, state); + kvm_x86_state_cleanup(state); + break; + case UCALL_ABORT: + REPORT_GUEST_ASSERT(uc); + /* NOT REACHED */ + case UCALL_DONE: + goto done; + default: + TEST_FAIL("Unknown ucall %lu", uc.cmd); + } + } +done: + kvm_vm_free(vm); +} + +int main(int argc, char *argv[]) +{ + TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SVM)); + TEST_REQUIRE(kvm_is_lbrv_enabled()); + + test_lbrv_nested_state(/*nested_lbrv=3D*/false); + test_lbrv_nested_state(/*nested_lbrv=3D*/true); + + return 0; +} --=20 2.53.0.473.g4a7958ca14-goog