From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0FA953769FF for ; Wed, 30 Sep 2026 21:25:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790803509; cv=none; b=j2l1Glj4tfJqNTfAsBCZCUTpmqSNwpWZhEIOm/iBR8HoTiDKlkn+uV5GCbhoQzDhJ2O4zS+fcFM20nI81r3CYDMeBXk5P6+i+7ckvW+CoCNkmFqdLLN6EKvEGv0k+UfwRBFYBqWTJ/BCoJePJylvnPrQuc5RWf0rTZFfrc4giXA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790803509; c=relaxed/simple; bh=eL1XyKnOjHtw5k0BfrK0G8yq6PsdfpMlLsRqwkMbIlQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VRpIqnrhmq/FxCjFkhLYISqzcp+NOc9e1qPG4hUxx3tIcWC6CMou7AqgiyfRjsvs+x+ZDm0Z3mqHDC8T6AdXIL6jzY1Ll4pguBat8VcfanqPOIPXLMh3xpdmsWHwYe0zv+h/SCGtqCyFyNwRwaH0pcM3wHVzUCcV4/CFuMNjj24= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZZQVqSHQ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZZQVqSHQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 141C41F000FF; Wed, 30 Sep 2026 21:25:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790803507; bh=kfMv9NqFU14fGG0JvhRGwpTgL8JASX/dWdyB8cvtJbE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ZZQVqSHQ5Y63HC7wzgR9sEGz/ryNMoxk12HAgdNMcvc/k03lnVVpkfoVN38fqOIog Q9BnD3/azhdkmpk6obkU61PC9x7RrF+xNhuo8mIFosOEzPAIUVm3Oy17Ee+SXaUKAR Fas7+F4CXYsff0rWmSUw8NpYR/efEKtupb4VIw+BlWZhaKR9fBz9OQEZuVpbL7oHvM mK40WIf1i7B4CSMh2+1BBWLtQUp3xeFDRi+1T7xiiY6NA4FB8Ja9YlMNnsStHYwBOg 7Qv2hEXFWYc746hP+ewH0K0qMJIC1T+00Sy+GYOVlstqqgE6fiU6pLfPgjqIP3npNQ vVDbUFJBMbJkg== From: Sasha Levin To: stable@vger.kernel.org Cc: Sean Christopherson , Vitaly Kuznetsov , Sasha Levin Subject: [PATCH 6.1.y 1/2] KVM: x86: Reject nested CAP enablement if nested virtualization is disabled Date: Wed, 30 Sep 2026 17:25:04 -0400 Message-ID: <20260930212505.3176940-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026092946-laxative-rival-2080@gregkh> References: <2026092946-laxative-rival-2080@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Sean Christopherson [ Upstream commit b65699be2c606d2687593516d93e66d16a713b61 ] 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") Reviewed-by: Vitaly Kuznetsov Link: https://patch.msgid.link/20260630202828.440724-2-seanjc@google.com Signed-off-by: Sean Christopherson Backport notes for 6.1: Keep the capability handler's existing function-scope declarations and add the nested-enabled check without importing the newer case-local block. Provide kvm_nested_call() as a macro around the existing nested_ops function pointer and use it for get_nested_state_pages(). Match the upstream blank line before that request handler so commit 10180a277549339020b08000206092c07e0bff5a applies unchanged. This preserves the current dispatch behavior without importing the static-call conversion or adding functions. The request re-pending fix remains in the target. Stable-dep-of: 10180a277549 ("KVM: x86: Re-pend GET_NESTED_STATE_PAGES if getting said pages fails") Signed-off-by: Sasha Levin --- arch/x86/include/asm/kvm_host.h | 4 ++++ arch/x86/kvm/hyperv.c | 3 ++- arch/x86/kvm/svm/svm.c | 1 + arch/x86/kvm/vmx/vmx.c | 1 + arch/x86/kvm/x86.c | 15 +++++++++------ 5 files changed, 17 insertions(+), 7 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 31395c43416dd..a4199606edfd0 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1643,6 +1643,8 @@ 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); @@ -1693,6 +1695,8 @@ extern struct kvm_x86_ops kvm_x86_ops; #define KVM_X86_OP_OPTIONAL_RET0 KVM_X86_OP #include +#define kvm_nested_call(func) (kvm_x86_ops.nested_ops->func) + int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops); void kvm_x86_vendor_exit(void); diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index bddeb5a28b23f..528da4e0f7e05 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -2457,7 +2457,8 @@ 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 && + kvm_x86_ops.nested_ops->get_evmcs_version) 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 88979fefaa284..b3fb174e11523 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -5110,6 +5110,7 @@ static __init int svm_hardware_setup(void) printk(KERN_INFO "kvm: Nested Virtualization enabled\n"); kvm_enable_efer_bits(EFER_SVME | EFER_LMSLE); } + 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 cc10bde20d451..557b1ab8ea358 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -8549,6 +8549,7 @@ static __init int hardware_setup(void) if (r) return r; } + vmx_nested_ops.enabled = nested; vmx_set_cpu_caps(); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ffbf532baf7cd..d5686a1ee3287 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4516,14 +4516,15 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = KVM_X2APIC_API_VALID_FLAGS; 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; case KVM_CAP_HYPERV_DIRECT_TLBFLUSH: r = kvm_x86_ops.enable_direct_tlbflush != 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; case KVM_CAP_SMALLER_MAXPHYADDR: r = (int) allow_smaller_maxphyaddr; @@ -5544,7 +5545,8 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu, return kvm_hv_activate_synic(vcpu, cap->cap == KVM_CAP_HYPERV_SYNIC2); case KVM_CAP_HYPERV_ENLIGHTENED_VMCS: - 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) { @@ -5899,7 +5901,7 @@ 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)); @@ -5929,7 +5931,7 @@ 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; @@ -10654,8 +10656,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) r = -EIO; goto out; } + if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) { - if (unlikely(!kvm_x86_ops.nested_ops->get_nested_state_pages(vcpu))) { + if (unlikely(!kvm_nested_call(get_nested_state_pages)(vcpu))) { r = 0; goto out; } -- 2.53.0