From nobody Mon Feb 9 00:31:15 2026 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6A2B6155A4E for ; Thu, 28 Nov 2024 01:34:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732757698; cv=none; b=fIpDFKjIX7gi0zoiQuMtlM8l8KEsbknZaD9nwCe3gEqV7NQv/1EaDHBgvI3mAB86mnJzZIsxXu4RYp4TTVs7D83sUNTOuuF2QXZmSLRK0qtX0bkELBYbgeBFDp2EyaI+TpjTgigLhI2FHnmEGNYUx4Ziqy876hnmH3Y+G6kp6dg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732757698; c=relaxed/simple; bh=7zC5azkES26WfDq3Whxv3so2ietZ4rGRL4pkkJDTXTA=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=FuEwgUw6k+x6BS163JjO7Rs+o/cKOKNaYulPNe1TMti/Anf65low4kPVmNFJ6eY5HlsVrsb199mPq7s84lnSr6BsD2Y7Hwndp+c1r5edNNAaoXWGZCLOcbsQzoKRpZzR5C6l5iJa06Fbr2YaAVChB60E3TLwAKDdorrs7sZNkvM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=twr2Tlwz; arc=none smtp.client-ip=209.85.216.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="twr2Tlwz" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-2ea3c9178f6so359583a91.1 for ; Wed, 27 Nov 2024 17:34:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1732757697; x=1733362497; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=/roR1Tq2E8S3SFqc2nnkeKb7VjdwQvlBDUindkJvlFg=; b=twr2Tlwzb7VcawOW2OvLME1sgRnCJIMCqhNgCNQO2AnHaq5HyUDA7cKVbLUD4GPApo 3b79h1zdAlu610uNrEnrP7mQNd7f3Po8sUm1mtbAadg46M7nCI5NkU7C/C3W2O4dQb9r yFQP/ix8p02n4P71TxsWumFfm7fel5yxQyJ0Joei8lPcsb+sVG9Iz4d8CYk1qQaCBP3s c1qg2weRw3Y2f2ChcKCbhMkycLcaWQCpgeB6ZsXN4JhZFPmwPJCbEgiGCcUyJDvoOENn HbBIbWYjX3mxAkOldMje7imUDl3O4/QsCJ+tNT2ruVFFSOdsULJf5IqVSo2Ix1RDxuWZ zu1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1732757697; x=1733362497; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=/roR1Tq2E8S3SFqc2nnkeKb7VjdwQvlBDUindkJvlFg=; b=EiwFn9e3suAQKRHE96JzVkSfcAHDs5VFk+VsvgIUutYm7yPPtfjg/IKXg1h/dFH3L5 i+rpjuzKpKfRs1q9h39ot18j4xg9olaRdQuSIYPBLp6kkcbChVIlVMh+M4Jeqe+Nlmvu Mi2W7V1bpssJEj5G1tVWneMrp0I1NL7/7GtsuaCom4N/VQnbT1TdyibBlVc2mNNlFrIE tdXTl7NMFM/MO9Lubs9y9cMtrxwh8dxiE4T3WGn4zOFkXMidFWG9H127gIxENC+feHcP lfStAfMlEsP2rks03X2oF4QhFiNXrReuk0CZdYNqSiWFeYWlZP8zjr3ukIATzwGKBJe8 4gFA== X-Forwarded-Encrypted: i=1; AJvYcCX9Ju2NKeYhRRTqIwTo9lafMZCWs8SS6lbUIps2grgR4tPTihizJJKQZYHLxdPpXumz2AF9drp8Cg7Ljf8=@vger.kernel.org X-Gm-Message-State: AOJu0Yz+qK/ZNVA/C257yNUruMMplwsj5jIDbDOh7/TX3LT04eGn/Q4P b0gNrPb1K0imX9OFxU++U5krpr/C7XbtMDuT+lkW7g3jvrCkUVu4b3X0k2m2iarfPNKrKYY9tIp 8FQ== X-Google-Smtp-Source: AGHT+IF6wH28m3FYKRZIpAFfWy3k4UMceR/PxneksITg/V4r6c3bKfb6SNvvACyGYnuBjppIhRKxes+QUjM= X-Received: from pjbsw12.prod.google.com ([2002:a17:90b:2c8c:b0:2e9:2437:ab4b]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:1d10:b0:2ea:aa56:4b0 with SMTP id 98e67ed59e1d1-2ee08e99941mr6405613a91.3.1732757696965; Wed, 27 Nov 2024 17:34:56 -0800 (PST) Reply-To: Sean Christopherson Date: Wed, 27 Nov 2024 17:33:41 -0800 In-Reply-To: <20241128013424.4096668-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20241128013424.4096668-15-seanjc@google.com> Subject: [PATCH v3 14/57] KVM: x86: Reject disabling of MWAIT/HLT interception when not allowed 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 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Reject KVM_CAP_X86_DISABLE_EXITS if userspace attempts to disable MWAIT or HLT exits and KVM previously reported (via KVM_CHECK_EXTENSION) that disabling the exit(s) is not allowed. E.g. because MWAIT isn't supported or the CPU doesn't have an always-running APIC timer, or because KVM is configured to mitigate cross-thread vulnerabilities. Cc: Kechen Lu Fixes: 4d5422cea3b6 ("KVM: X86: Provide a capability to disable MWAIT inter= cepts") Fixes: 6f0f2d5ef895 ("KVM: x86: Mitigate the cross-thread return address pr= edictions bug") Reviewed-by: Maxim Levitsky Reviewed-by: Xiaoyao Li Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 54 ++++++++++++++++++++++++---------------------- 1 file changed, 28 insertions(+), 26 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c517d26f2c5b..9b7f8047f896 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4531,6 +4531,20 @@ static inline bool kvm_can_mwait_in_guest(void) boot_cpu_has(X86_FEATURE_ARAT); } =20 +static u64 kvm_get_allowed_disable_exits(void) +{ + u64 r =3D KVM_X86_DISABLE_EXITS_PAUSE; + + if (!mitigate_smt_rsb) { + r |=3D KVM_X86_DISABLE_EXITS_HLT | + KVM_X86_DISABLE_EXITS_CSTATE; + + if (kvm_can_mwait_in_guest()) + r |=3D KVM_X86_DISABLE_EXITS_MWAIT; + } + return r; +} + #ifdef CONFIG_KVM_HYPERV static int kvm_ioctl_get_supported_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 __user *cpuid_arg) @@ -4673,15 +4687,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, lo= ng ext) r =3D KVM_CLOCK_VALID_FLAGS; break; case KVM_CAP_X86_DISABLE_EXITS: - r =3D KVM_X86_DISABLE_EXITS_PAUSE; - - if (!mitigate_smt_rsb) { - r |=3D KVM_X86_DISABLE_EXITS_HLT | - KVM_X86_DISABLE_EXITS_CSTATE; - - if (kvm_can_mwait_in_guest()) - r |=3D KVM_X86_DISABLE_EXITS_MWAIT; - } + r =3D kvm_get_allowed_disable_exits(); break; case KVM_CAP_X86_SMM: if (!IS_ENABLED(CONFIG_KVM_SMM)) @@ -6528,33 +6534,29 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, break; case KVM_CAP_X86_DISABLE_EXITS: r =3D -EINVAL; - if (cap->args[0] & ~KVM_X86_DISABLE_VALID_EXITS) + if (cap->args[0] & ~kvm_get_allowed_disable_exits()) break; =20 mutex_lock(&kvm->lock); if (kvm->created_vcpus) goto disable_exits_unlock; =20 - if (cap->args[0] & KVM_X86_DISABLE_EXITS_PAUSE) - kvm->arch.pause_in_guest =3D true; - #define SMT_RSB_MSG "This processor is affected by the Cross-Thread Return= Predictions vulnerability. " \ "KVM_CAP_X86_DISABLE_EXITS should only be used with SMT disabled or = trusted guests." =20 - if (!mitigate_smt_rsb) { - if (boot_cpu_has_bug(X86_BUG_SMT_RSB) && cpu_smt_possible() && - (cap->args[0] & ~KVM_X86_DISABLE_EXITS_PAUSE)) - pr_warn_once(SMT_RSB_MSG); - - if ((cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT) && - kvm_can_mwait_in_guest()) - kvm->arch.mwait_in_guest =3D true; - if (cap->args[0] & KVM_X86_DISABLE_EXITS_HLT) - kvm->arch.hlt_in_guest =3D true; - if (cap->args[0] & KVM_X86_DISABLE_EXITS_CSTATE) - kvm->arch.cstate_in_guest =3D true; - } + if (!mitigate_smt_rsb && boot_cpu_has_bug(X86_BUG_SMT_RSB) && + cpu_smt_possible() && + (cap->args[0] & ~KVM_X86_DISABLE_EXITS_PAUSE)) + pr_warn_once(SMT_RSB_MSG); =20 + if (cap->args[0] & KVM_X86_DISABLE_EXITS_PAUSE) + kvm->arch.pause_in_guest =3D true; + if (cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT) + kvm->arch.mwait_in_guest =3D true; + if (cap->args[0] & KVM_X86_DISABLE_EXITS_HLT) + kvm->arch.hlt_in_guest =3D true; + if (cap->args[0] & KVM_X86_DISABLE_EXITS_CSTATE) + kvm->arch.cstate_in_guest =3D true; r =3D 0; disable_exits_unlock: mutex_unlock(&kvm->lock); --=20 2.47.0.338.g60cca15819-goog