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[146.148.121.110]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-498010aade3sm84008685e9.14.2026.07.30.11.24.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jul 2026 11:24:30 -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 0/3] KVM: x86: Fix off-by-one in max_vcpu_ids bounds checks Date: Thu, 30 Jul 2026 18:24:22 +0000 Message-ID: <20260730182425.1223530-1-dmaluka@chromium.org> X-Mailer: git-send-email 2.55.0.508.g3f0d502094-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit max_vcpu_ids and KVM_CAP_MAX_VCPU_ID are exclusive, i.e. the maximum allowed vcpu_id value is max_vcpu_ids minus one, not max_vcpu_ids. Fix the sanity checks for KVM_SET_BOOT_CPU_ID and KVM_CAP_MAX_VCPU_ID and the selftests for them (added in series [1]) to fail when bsp_vcpu_id is incorrectly set to max_vcpu_ids, not to a value below max_vcpu_ids. Also clarify that in the documentation of KVM_CAP_MAX_VCPU_ID, in an attempt to make this a bit less confusing. [1] https://lore.kernel.org/all/20240614202859.3597745-1-minipli@grsecurity.net/ Dmytro Maluka (3): KVM: selftests: Fix treating KVM_CAP_MAX_VCPU_ID as inclusive KVM: x86: Fix off-by-one in max_vcpu_ids bounds checks Documentation: KVM: Clarify that KVM_CAP_MAX_VCPU_ID is exclusive Documentation/virt/kvm/api.rst | 13 ++++++++----- arch/x86/kvm/x86.c | 6 +++--- .../selftests/kvm/x86/max_vcpuid_cap_test.c | 17 ++++++++++------- .../testing/selftests/kvm/x86/set_boot_cpu_id.c | 4 ++-- 4 files changed, 23 insertions(+), 17 deletions(-) -- 2.55.0.508.g3f0d502094-goog