From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 B5B5026CE33; Fri, 21 Nov 2025 13:25:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763731547; cv=none; b=NBGQxIRIVN90m24FocStwnn8ovVow7VHgK6uPkTiQ5cT0eZXjLdip7fKJ6YPfs+0xxxub7omiOI0SWwz1khvHM/EFjmS4ZaTQwr/mVqz7qzgMv58v2h7cl8RTxk4B8nFl3fka40vaeO8qp9L2eLG/Ssw54yQoxG2xI7skiM5ymk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763731547; c=relaxed/simple; bh=riBUUv50CNB3VKebqEbQ5S7zEb+twqNwbdqIsFHtus4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=My1PgsYjEcxN1woHIcY/sekSuq9gWdTnvo8+3fi53FlZ3+QkAuvGUEz0PMm1farT0WGjfqP2t6s/MvpAEfyy2LzVYN8K7Pm+wvc6VRitKWebTg3cgVaseEpnThxPG9TzQCmOjJ3gffUIx/FxbBgXjC9yeuPXhi3W6VDGEgCYbVs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=IvbXeWkI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="IvbXeWkI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E90E7C4CEF1; Fri, 21 Nov 2025 13:25:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1763731546; bh=riBUUv50CNB3VKebqEbQ5S7zEb+twqNwbdqIsFHtus4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IvbXeWkI1DeoaWSXhVCISbka8nCTmK/gQLHijOOi3v1nMDk+3Y3RlmtGoXxOkwrpD gH6GxKEj3d9seLIb1KQOuBDHJ9Bl8BOpj1oHJT2ZICjCzb5YF8MBbeOLicYv8U9C/r CEYZZztrX62VEBE56D0LsI3dG8suP+Lf2YoMnInI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kai Huang , Xiaoyao Li , Rick Edgecombe , Dan Williams , Binbin Wu , Sean Christopherson , Sasha Levin Subject: [PATCH 6.17 245/247] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or TDCALL Date: Fri, 21 Nov 2025 14:13:12 +0100 Message-ID: <20251121130203.534520650@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251121130154.587656062@linuxfoundation.org> References: <20251121130154.587656062@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sean Christopherson [ Upstream commit 9d7dfb95da2cb5c1287df2f3468bcb70d8b31087 ] Add VMX exit handlers for SEAMCALL and TDCALL to inject a #UD if a non-TD guest attempts to execute SEAMCALL or TDCALL. Neither SEAMCALL nor TDCALL is gated by any software enablement other than VMXON, and so will generate a VM-Exit instead of e.g. a native #UD when executed from the guest kernel. Note! No unprivileged DoS of the L1 kernel is possible as TDCALL and SEAMCALL #GP at CPL > 0, and the CPL check is performed prior to the VMX non-root (VM-Exit) check, i.e. userspace can't crash the VM. And for a nested guest, KVM forwards unknown exits to L1, i.e. an L2 kernel can crash itself, but not L1. Note #2! The Intel® Trust Domain CPU Architectural Extensions spec's pseudocode shows the CPL > 0 check for SEAMCALL coming _after_ the VM-Exit, but that appears to be a documentation bug (likely because the CPL > 0 check was incorrectly bundled with other lower-priority #GP checks). Testing on SPR and EMR shows that the CPL > 0 check is performed before the VMX non-root check, i.e. SEAMCALL #GPs when executed in usermode. Note #3! The aforementioned Trust Domain spec uses confusing pseudocode that says that SEAMCALL will #UD if executed "inSEAM", but "inSEAM" specifically means in SEAM Root Mode, i.e. in the TDX-Module. The long- form description explicitly states that SEAMCALL generates an exit when executed in "SEAM VMX non-root operation". But that's a moot point as the TDX-Module injects #UD if the guest attempts to execute SEAMCALL, as documented in the "Unconditionally Blocked Instructions" section of the TDX-Module base specification. Cc: stable@vger.kernel.org Cc: Kai Huang Cc: Xiaoyao Li Cc: Rick Edgecombe Cc: Dan Williams Cc: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Binbin Wu Reviewed-by: Xiaoyao Li Link: https://lore.kernel.org/r/20251016182148.69085-2-seanjc@google.com Signed-off-by: Sean Christopherson Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/uapi/asm/vmx.h | 1 + arch/x86/kvm/vmx/nested.c | 8 ++++++++ arch/x86/kvm/vmx/vmx.c | 8 ++++++++ 3 files changed, 17 insertions(+) --- a/arch/x86/include/uapi/asm/vmx.h +++ b/arch/x86/include/uapi/asm/vmx.h @@ -93,6 +93,7 @@ #define EXIT_REASON_TPAUSE 68 #define EXIT_REASON_BUS_LOCK 74 #define EXIT_REASON_NOTIFY 75 +#define EXIT_REASON_SEAMCALL 76 #define EXIT_REASON_TDCALL 77 #define EXIT_REASON_MSR_READ_IMM 84 #define EXIT_REASON_MSR_WRITE_IMM 85 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -6587,6 +6587,14 @@ static bool nested_vmx_l1_wants_exit(str case EXIT_REASON_NOTIFY: /* Notify VM exit is not exposed to L1 */ return false; + case EXIT_REASON_SEAMCALL: + case EXIT_REASON_TDCALL: + /* + * SEAMCALL and TDCALL unconditionally VM-Exit, but aren't + * virtualized by KVM for L1 hypervisors, i.e. L1 should + * never want or expect such an exit. + */ + return false; default: return true; } --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -5953,6 +5953,12 @@ static int handle_vmx_instruction(struct return 1; } +static int handle_tdx_instruction(struct kvm_vcpu *vcpu) +{ + kvm_queue_exception(vcpu, UD_VECTOR); + return 1; +} + #ifndef CONFIG_X86_SGX_KVM static int handle_encls(struct kvm_vcpu *vcpu) { @@ -6078,6 +6084,8 @@ static int (*kvm_vmx_exit_handlers[])(st [EXIT_REASON_ENCLS] = handle_encls, [EXIT_REASON_BUS_LOCK] = handle_bus_lock_vmexit, [EXIT_REASON_NOTIFY] = handle_notify, + [EXIT_REASON_SEAMCALL] = handle_tdx_instruction, + [EXIT_REASON_TDCALL] = handle_tdx_instruction, [EXIT_REASON_MSR_READ_IMM] = handle_rdmsr_imm, [EXIT_REASON_MSR_WRITE_IMM] = handle_wrmsr_imm, };