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 8B3F0368DE1 for ; Thu, 20 Nov 2025 19:07:13 +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=1763665633; cv=none; b=uE31LqWb54WdqIFW6iMYe0orvTHAwTtV15BecrrOLmp4ml2mfn8+C2IiC72/UNJUS1lUJqaSlCluiPlAyMKHOwWIkUX5eWovVfsmegxAW8SL/oz7GXG4rg88tz7jWmQtWycll9sQFtHdwX6ZJpZkG0DAQkvjNp5/o7xLHEJ4rNg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763665633; c=relaxed/simple; bh=Dw8vHW3X+dLiS6nQJ0h0qLNdhiddcXaugr9g7u9Pgko=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=s91XdO6NScOYu11mLYDb6e1GGLubZLfKDg8lG+veo4a4TCbiaOP7uG234A2miaSAy9t0z6vfFfzMs/ZNc8BxnkpQWuQP8rb0yxkdkchslDGqGJNs+weeSsvTE74TxJJTMGARit7fyG4c4KY6txuq+vc6XfaQHmE6FPa6Fc0Bdnk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SzubWlIz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="SzubWlIz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4178BC16AAE; Thu, 20 Nov 2025 19:07:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763665633; bh=Dw8vHW3X+dLiS6nQJ0h0qLNdhiddcXaugr9g7u9Pgko=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SzubWlIzepbG/4h12ZGqtHtKEL5xhMvz59Mhv7R4wIiJHnui91ErXz1CveaAPU5k/ 9JAvhO/AHtNgrHerflipgkRKpPTPrQ1bLfzZhW/szH/p5ejnsDR60PCRJ/bXXLDhB5 felj2aD8M37YdTcocSnS0IP3z4mjo9Nkl0XczWL+c0Ej5R17w+1U4ad+E3VNTbxbJ4 0xy/vpPuDa/Dh12mLXynjN3EXLPjCFPz84LVx95P0hmYh7zzusv/4R0w9e6I7aV1pe bhkSEITjPyCkDcWf5LWxxgJFGr2vEmydR46ElLaXHSs3InF3TuNAkiZ+5MD+GIVQQb zRrVhi9n9ZQsQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Sean Christopherson , Kai Huang , Xiaoyao Li , Rick Edgecombe , Dan Williams , Binbin Wu , Sasha Levin Subject: [PATCH 6.17.y 3/3] KVM: VMX: Inject #UD if guest tries to execute SEAMCALL or TDCALL Date: Thu, 20 Nov 2025 14:07:07 -0500 Message-ID: <20251120190708.2275081-3-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251120190708.2275081-1-sashal@kernel.org> References: <2025112027-ranch-retool-efaa@gregkh> <20251120190708.2275081-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 --- 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(+) diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h index 9792e329343e8..1baa86dfe0293 100644 --- 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 diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 4e6352ef95201..c66145aca2d8d 100644 --- 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(struct kvm_vcpu *vcpu, 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; } diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 4d1af365f5845..7bd1679634e93 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -5953,6 +5953,12 @@ static int handle_vmx_instruction(struct kvm_vcpu *vcpu) 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[])(struct kvm_vcpu *vcpu) = { [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, }; -- 2.51.0