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[146.148.121.110]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-498010aade3sm84008685e9.14.2026.07.30.11.24.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jul 2026 11:24:32 -0700 (PDT) From: Dmytro Maluka To: Sean Christopherson Cc: Paolo Bonzini , Dave Hansen , Mathias Krause , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Vineeth Pillai , Chuanxiao Dong , Aashish Sharma , Grzegorz Jaszczyk , Dmytro Maluka Subject: [PATCH 1/3] KVM: selftests: Fix treating KVM_CAP_MAX_VCPU_ID as inclusive Date: Thu, 30 Jul 2026 18:24:23 +0000 Message-ID: <20260730182425.1223530-2-dmaluka@chromium.org> X-Mailer: git-send-email 2.55.0.508.g3f0d502094-goog In-Reply-To: <20260730182425.1223530-1-dmaluka@chromium.org> References: <20260730182425.1223530-1-dmaluka@chromium.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit KVM_CAP_MAX_VCPU_ID is (confusingly) exclusive, i.e. the maximum allowed vcpu_id value is KVM_CAP_MAX_VCPU_ID minus one. Some tests in x86/max_vcpuid_cap_test.c and kvm/x86/set_boot_cpu_id.c mistakenly treat it as inclusive, in particular, assume that setting bsp_vcpu_id to KVM_CAP_MAX_VCPU_ID is valid and should succeed. Fix those tests. Fixes: 4b451a57809c ("KVM: selftests: Test max vCPU IDs corner cases") Fixes: 438a496b9041 ("KVM: selftests: Test vCPU boot IDs above 2^32 and MAX_VCPU_ID") Signed-off-by: Dmytro Maluka --- .../selftests/kvm/x86/max_vcpuid_cap_test.c | 17 ++++++++++------- .../testing/selftests/kvm/x86/set_boot_cpu_id.c | 4 ++-- 2 files changed, 12 insertions(+), 9 deletions(-) diff --git a/tools/testing/selftests/kvm/x86/max_vcpuid_cap_test.c b/tools/testing/selftests/kvm/x86/max_vcpuid_cap_test.c index 7e2bfb3c3f3b..43f16c052de4 100644 --- a/tools/testing/selftests/kvm/x86/max_vcpuid_cap_test.c +++ b/tools/testing/selftests/kvm/x86/max_vcpuid_cap_test.c @@ -30,22 +30,25 @@ int main(int argc, char *argv[]) if (kvm_has_cap(KVM_CAP_SET_BOOT_CPU_ID)) { vm_ioctl(vm, KVM_SET_BOOT_CPU_ID, (void *)MAX_VCPU_ID); - /* Try setting KVM_CAP_MAX_VCPU_ID below BOOT_CPU_ID */ - ret = __vm_enable_cap(vm, KVM_CAP_MAX_VCPU_ID, MAX_VCPU_ID - 1); + /* Try setting KVM_CAP_MAX_VCPU_ID below or equal to BOOT_CPU_ID */ + ret = __vm_enable_cap(vm, KVM_CAP_MAX_VCPU_ID, MAX_VCPU_ID); TEST_ASSERT(ret < 0, - "Setting KVM_CAP_MAX_VCPU_ID below BOOT_CPU_ID should fail"); + "Setting KVM_CAP_MAX_VCPU_ID <= BOOT_CPU_ID should fail"); } - /* Set KVM_CAP_MAX_VCPU_ID */ - vm_enable_cap(vm, KVM_CAP_MAX_VCPU_ID, MAX_VCPU_ID); + /* + * Set KVM_CAP_MAX_VCPU_ID. Note: KVM_CAP_MAX_VCPU_ID is a misnomer, + * it actually represents maximum vcpu_id plus one. + */ + vm_enable_cap(vm, KVM_CAP_MAX_VCPU_ID, MAX_VCPU_ID + 1); /* Try to set KVM_CAP_MAX_VCPU_ID again */ - ret = __vm_enable_cap(vm, KVM_CAP_MAX_VCPU_ID, MAX_VCPU_ID + 1); + ret = __vm_enable_cap(vm, KVM_CAP_MAX_VCPU_ID, MAX_VCPU_ID + 2); TEST_ASSERT(ret < 0, "Setting KVM_CAP_MAX_VCPU_ID multiple times should fail"); /* Create vCPU with id beyond KVM_CAP_MAX_VCPU_ID cap */ - ret = __vm_ioctl(vm, KVM_CREATE_VCPU, (void *)MAX_VCPU_ID); + ret = __vm_ioctl(vm, KVM_CREATE_VCPU, (void *)(MAX_VCPU_ID + 1)); TEST_ASSERT(ret < 0, "Creating vCPU with ID > MAX_VCPU_ID should fail"); /* Create vCPU with bits 63:32 != 0, but an otherwise valid id */ diff --git a/tools/testing/selftests/kvm/x86/set_boot_cpu_id.c b/tools/testing/selftests/kvm/x86/set_boot_cpu_id.c index 8e3898646c69..1c4ebdf8e82c 100644 --- a/tools/testing/selftests/kvm/x86/set_boot_cpu_id.c +++ b/tools/testing/selftests/kvm/x86/set_boot_cpu_id.c @@ -39,8 +39,8 @@ static void test_set_invalid_bsp(struct kvm_vm *vm) int r; if (max_vcpu_id) { - r = __vm_ioctl(vm, KVM_SET_BOOT_CPU_ID, (void *)(max_vcpu_id + 1)); - TEST_ASSERT(r == -1 && errno == EINVAL, "BSP with ID > MAX should fail"); + r = __vm_ioctl(vm, KVM_SET_BOOT_CPU_ID, (void *)max_vcpu_id); + TEST_ASSERT(r == -1 && errno == EINVAL, "BSP with ID >= MAX should fail"); } r = __vm_ioctl(vm, KVM_SET_BOOT_CPU_ID, (void *)(1L << 32)); -- 2.55.0.508.g3f0d502094-goog