From mboxrd@z Thu Jan 1 00:00:00 1970 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 F38963403F4 for ; Thu, 25 Jun 2026 23:38:49 +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=1782430731; cv=none; b=MOQZ574DrcWT5Eu6DojRM+RMcGQX7skN9WXdR9R26uibUl+okenkHLRZnHcPoMC1vHqN/FVFI9XhWuWpT2ow64Kmja7WLsR97RrvN+SG3LOvb96DLEOukd5YRwNH3jQ3h4soGFo9wHiytYHz8DOT9QdbjDW1x97I07dpy3ql4dQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782430731; c=relaxed/simple; bh=FJK1hvciw80QOY6xpCGROLsoY9Vu9CvbZULGZu2jKNw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=MA5usydEpiZQJ2sHj313NeGGNCv6zKoo+tHgXZ1I1RryRBcGiHpJg3SvOGnc1XnOa5P0voGRTOpJ/06tqOY+CPeoK65HS7/etJltnHpFUS4tzs3hXEe84aySyUSs7Wy0WYohmPpUy5vWpZNKehHTwnSWLf16WG8cCwhbRX+QS8Q= 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=lVIhWFnI; 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="lVIhWFnI" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-37df6354960so233567a91.2 for ; Thu, 25 Jun 2026 16:38:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1782430729; x=1783035529; 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=tZsf/kVM3uzl+IfL0/RYiugpT8VJMpZAex4og4Whr3I=; b=lVIhWFnIrhKMJBtY8+BDqNXl+WrDXwl/FVIs5Bx/2Et6gWy+h8qR29lL/gsAh8+8NV eZ3DF2dBeXtUJg8QRfkS+WJPJtRiXKtzuQDdVeumtmqB3NgqXchNDlilemb6XLNtQceE hTL6Ik2iAlUudazeHMmreRjgxpEj7KB6UYYzv2O/RC4uSI654mZqIyhyPBzp5BVwk70i J2wFmCovWykBv5OxDRZKs/DBUvjpBG+xTYd/xQir/vuGnCmeR+XfzuzWmoOpQrbJpZHo 64UY4F7eZdbPKw/30HjFP1a25Zq15ibsuGcuAJ90Naw3/qKlFOGg36s+oBA+AbSBZ8jU CiZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782430729; x=1783035529; 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=tZsf/kVM3uzl+IfL0/RYiugpT8VJMpZAex4og4Whr3I=; b=X+kkxy6QhBwPSH+CwjPUU7RnfpnKTI+yFZveEkJeGHoAE8PJptBEFlDVey45qu6rkm VX1PWY+j+azD40gU1kR7oQBqR/osApr5JdZI4JSUnF9059hCR35anvtEoj0TN7Mf0tDh UTgP8A3nzINhU9mWms+fl+mjQ0zEKv8gSwnsVBRsgkY4k7Y/SldDskM2mHRYqRyP1I71 YNjdhxb5GT/o9k8/ipGfbvD5KiDVhvZA9aViajRH7QXr2syrk928LMtDiwp0bDQ/7fT0 9LrP+ODLCY4VKzPjB1br4FwEcecLN4GuJ44znVuBoaYEljwTao0efbay0zjDtcfKUkn3 gneQ== X-Forwarded-Encrypted: i=1; AHgh+RpN30Rdy0GFA8Sy9umhFp12D9o040D7dDq5foZd0MIGD/oiaMnkIPVRK6NghWPh7K9voNeUl6KpfpwqDs0=@vger.kernel.org X-Gm-Message-State: AOJu0Yz/qRA14U4gUdOKvq+nq7aalKLiLugfMQKlFWRIA71hQ4dqqISp 2aHr37yfvWOMgt6GFtk89jlMgzdQPCy4kHLf87fpSuIjXzsjHCGdNU/+CLBdeHxFjWglYD7Gdxe 1TiMhGw== X-Received: from pjvd15.prod.google.com ([2002:a17:90a:d98f:b0:36b:dc35:1b43]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:4c50:b0:36d:bbe0:de7c with SMTP id 98e67ed59e1d1-37dfa2363femr3936293a91.12.1782430728827; Thu, 25 Jun 2026 16:38:48 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 25 Jun 2026 16:38:44 -0700 In-Reply-To: <20260625233846.3407303-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260625233846.3407303-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.rc0.799.gd6f94ed593-goog Message-ID: <20260625233846.3407303-2-seanjc@google.com> Subject: [PATCH 1/3] KVM: x86: Reject nested CAP enablement if nested virtualization is disabled From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini , Vitaly Kuznetsov Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Add a flag to explicitly track if nested virtualization is enabled, and use it enumerate that various nested CAPs are unsupported, and to reject enablement of said CAPs. When the nested ops hooks were moved to their own structure, KVM's NULL-by-default behavior was deliberately dropped, with the changelog asserting that all was well. That wasn't quite true; there is no danger to KVM, but now KVM is over-reporting support for KVM_CAP_NESTED_STATE and KVM_CAP_HYPERV_ENLIGHTENED_VMCS. Fixes: 33b22172452f ("KVM: x86: move nested-related kvm_x86_ops to a separate struct") Signed-off-by: Sean Christopherson --- arch/x86/include/asm/kvm_host.h | 2 ++ arch/x86/kvm/hyperv.c | 2 +- arch/x86/kvm/svm/svm.c | 1 + arch/x86/kvm/vmx/vmx.c | 1 + arch/x86/kvm/x86.c | 12 +++++++----- 5 files changed, 12 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index b517257a6315..36de689a579c 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1906,6 +1906,8 @@ struct kvm_x86_ops { }; struct kvm_x86_nested_ops { + bool enabled; + void (*leave_nested)(struct kvm_vcpu *vcpu); bool (*is_exception_vmexit)(struct kvm_vcpu *vcpu, u8 vector, u32 error_code); diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 1ee0d23f8949..fe951c196706 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -2787,7 +2787,7 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, }; int i, nent = ARRAY_SIZE(cpuid_entries); - if (kvm_x86_ops.nested_ops->get_evmcs_version) + if (kvm_x86_ops.nested_ops->enabled) evmcs_ver = kvm_x86_ops.nested_ops->get_evmcs_version(vcpu); if (cpuid->nent < nent) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index ef69a51ab27f..163440fca59f 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -5646,6 +5646,7 @@ static __init int svm_hardware_setup(void) if (r) return r; } + svm_nested_ops.enabled = nested; /* * KVM's MMU doesn't support using 2-level paging for itself, and thus diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 3681d565f177..ef9e1bc39edb 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -8786,6 +8786,7 @@ __init int vmx_hardware_setup(void) if (r) return r; } + vmx_nested_ops.enabled = nested; kvm_set_posted_intr_wakeup_handler(pi_wakeup_handler); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 0626e835e9eb..cd9a5ff47f6f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2346,7 +2346,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r &= ~KVM_X2APIC_ENABLE_SUPPRESS_EOI_BROADCAST; break; case KVM_CAP_NESTED_STATE: - r = kvm_x86_ops.nested_ops->get_state ? + r = kvm_x86_ops.nested_ops->enabled ? kvm_x86_ops.nested_ops->get_state(NULL, NULL, 0) : 0; break; #ifdef CONFIG_KVM_HYPERV @@ -2354,7 +2354,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = kvm_x86_ops.enable_l2_tlb_flush != NULL; break; case KVM_CAP_HYPERV_ENLIGHTENED_VMCS: - r = kvm_x86_ops.nested_ops->enable_evmcs != NULL; + r = kvm_x86_ops.nested_ops->enabled && + kvm_x86_ops.nested_ops->enable_evmcs != NULL; break; #endif case KVM_CAP_SMALLER_MAXPHYADDR: @@ -3366,7 +3367,8 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu, uint16_t vmcs_version; void __user *user_ptr; - if (!kvm_x86_ops.nested_ops->enable_evmcs) + if (!kvm_x86_ops.nested_ops->enabled || + !kvm_x86_ops.nested_ops->enable_evmcs) return -ENOTTY; r = kvm_x86_ops.nested_ops->enable_evmcs(vcpu, &vmcs_version); if (!r) { @@ -3732,7 +3734,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp, u32 user_data_size; r = -EINVAL; - if (!kvm_x86_ops.nested_ops->get_state) + if (!kvm_x86_ops.nested_ops->enabled) break; BUILD_BUG_ON(sizeof(user_data_size) != sizeof(user_kvm_nested_state->size)); @@ -3762,7 +3764,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp, int idx; r = -EINVAL; - if (!kvm_x86_ops.nested_ops->set_state) + if (!kvm_x86_ops.nested_ops->enabled) break; r = -EFAULT; -- 2.55.0.rc0.799.gd6f94ed593-goog