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AJvYcCUw2bBcS4FJ0ZUfa4a8XYmqx/pQf0kmPiLaKIEHi9mRnKgCn6LKZksv1JsDwtsavDX/2h/h/ukC5kc=@vger.kernel.org X-Gm-Message-State: AOJu0YxqT2eqmXI+p5FgrQrLVUm3z1Hv0pfV9WXXSpQ4D9KjPHzT41Iw ThVmFQ0k2/zo73VaiDcF1cwPo0NPw3wzcGcYjnT4cFnL5/BvNi//N8niS+D5kQ9twJTmnPFyK9b eHQ== X-Google-Smtp-Source: AGHT+IHqvArLP/DTLOy9MpelaMy9pJau/26PUrYe6mAmbmDCvrOFJgFkHYoGtDP5b19XPXc68OHJeJQvhkI= X-Received: from pgbdl2.prod.google.com ([2002:a05:6a02:d02:b0:7fc:219e:bdd9]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6e02:20e3:b0:3a7:87f2:b010 with SMTP id e9e14a558f8ab-3a7c552574bmr59060575ab.5.1732757720946; Wed, 27 Nov 2024 17:35:20 -0800 (PST) Reply-To: Sean Christopherson Date: Wed, 27 Nov 2024 17:33:55 -0800 In-Reply-To: <20241128013424.4096668-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-sgx@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241128013424.4096668-1-seanjc@google.com> X-Mailer: git-send-email 2.47.0.338.g60cca15819-goog Message-ID: <20241128013424.4096668-29-seanjc@google.com> Subject: [PATCH v3 28/57] KVM: x86: Harden CPU capabilities processing against out-of-scope features From: Sean Christopherson To: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Jarkko Sakkinen Cc: kvm@vger.kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, Maxim Levitsky , Hou Wenlong , Xiaoyao Li , Kechen Lu , Oliver Upton , Binbin Wu , Yang Weijiang , Robert Hoo Add compile-time assertions to verify that usage of F() and friends in kvm_set_cpu_caps() is scoped to the correct CPUID word, e.g. to detect bugs where KVM passes a feature bit from word X into word y. Add a one-off assertion in the aliased feature macro to ensure that only word 0x8000_0001.EDX aliased the features defined for 0x1.EDX. To do so, convert kvm_cpu_cap_init() to a macro and have it define a local variable to track which CPUID word is being initialized that is then used to validate usage of F() (all of the inputs are compile-time constants and thus can be fed into BUILD_BUG_ON()). Redefine KVM_VALIDATE_CPU_CAP_USAGE after kvm_set_cpu_caps() to be a nop so that F() can be used in other flows that aren't as easily hardened, e.g. __do_cpuid_func_emulated() and __do_cpuid_func(). Invoke KVM_VALIDATE_CPU_CAP_USAGE() in SF() and X86_64_F() to ensure the validation occurs, e.g. if the usage of F() is completely compiled out (which shouldn't happen for boot_cpu_has(), but could happen in the future, e.g. if KVM were to use cpu_feature_enabled()). Signed-off-by: Sean Christopherson --- arch/x86/kvm/cpuid.c | 51 ++++++++++++++++++++++++++++++-------------- 1 file changed, 35 insertions(+), 16 deletions(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index efff83da3df3..c9a8513dbc30 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -602,35 +602,53 @@ static __always_inline u32 raw_cpuid_get(struct cpuid_reg cpuid) return *__cpuid_entry_get_reg(&entry, cpuid.reg); } -static __always_inline void kvm_cpu_cap_init(u32 leaf, u32 mask) -{ - const struct cpuid_reg cpuid = x86_feature_cpuid(leaf * 32); +/* + * For kernel-defined leafs, mask the boot CPU's pre-populated value. For KVM- + * defined leafs, explicitly set the leaf, as KVM is the one and only authority. + */ +#define kvm_cpu_cap_init(leaf, mask) \ +do { \ + const struct cpuid_reg cpuid = x86_feature_cpuid(leaf * 32); \ + const u32 __maybe_unused kvm_cpu_cap_init_in_progress = leaf; \ + \ + if (leaf < NCAPINTS) \ + kvm_cpu_caps[leaf] &= (mask); \ + else \ + kvm_cpu_caps[leaf] = (mask); \ + \ + kvm_cpu_caps[leaf] &= raw_cpuid_get(cpuid); \ +} while (0) - /* - * For kernel-defined leafs, mask the boot CPU's pre-populated value. - * For KVM-defined leafs, explicitly set the leaf, as KVM is the one - * and only authority. - */ - if (leaf < NCAPINTS) - kvm_cpu_caps[leaf] &= mask; - else - kvm_cpu_caps[leaf] = mask; +/* + * Assert that the feature bit being declared, e.g. via F(), is in the CPUID + * word that's being initialized. Exempt 0x8000_0001.EDX usage of 0x1.EDX + * features, as AMD duplicated many 0x1.EDX features into 0x8000_0001.EDX. + */ +#define KVM_VALIDATE_CPU_CAP_USAGE(name) \ +do { \ + u32 __leaf = __feature_leaf(X86_FEATURE_##name); \ + \ + BUILD_BUG_ON(__leaf != kvm_cpu_cap_init_in_progress); \ +} while (0) - kvm_cpu_caps[leaf] &= raw_cpuid_get(cpuid); -} - -#define F feature_bit +#define F(name) \ +({ \ + KVM_VALIDATE_CPU_CAP_USAGE(name); \ + feature_bit(name); \ +}) /* Scattered Flag - For features that are scattered by cpufeatures.h. */ #define SF(name) \ ({ \ BUILD_BUG_ON(X86_FEATURE_##name >= MAX_CPU_FEATURES); \ + KVM_VALIDATE_CPU_CAP_USAGE(name); \ (boot_cpu_has(X86_FEATURE_##name) ? F(name) : 0); \ }) /* Features that KVM supports only on 64-bit kernels. */ #define X86_64_F(name) \ ({ \ + KVM_VALIDATE_CPU_CAP_USAGE(name); \ (IS_ENABLED(CONFIG_X86_64) ? F(name) : 0); \ }) @@ -641,6 +659,7 @@ static __always_inline void kvm_cpu_cap_init(u32 leaf, u32 mask) #define ALIASED_1_EDX_F(name) \ ({ \ BUILD_BUG_ON(__feature_leaf(X86_FEATURE_##name) != CPUID_1_EDX); \ + BUILD_BUG_ON(kvm_cpu_cap_init_in_progress != CPUID_8000_0001_EDX); \ feature_bit(name); \ })