From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.15]) (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 3FA55221F1C; Wed, 28 Jan 2026 06:38:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769582328; cv=none; b=N2MCeKI+vmKJddfopm0h4qpRfQ6Ucl6Nr6xqmAQp1ao7L8isV2R0TG4rvmUOKp5I8JAjVlL1bMD+ZJduhIzREd+FdXq44VQzmREF7J8tzwfjgx5hGD+N+Y0zyGT3DXkPfd4WndMEHKcVy8Rpn47EFeU/4XuhAmUnuQW/rq+vx3k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769582328; c=relaxed/simple; bh=01udh5m7XfU/YSuKGZba1QVK13n4mcDm9i4gsTeixnw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=T7gmbNU4MuBbimFWeJglns4WkAC8mQu24HnxwBy8q2aIrRx3HCHanCv/jIyinO85wCV4Gs3PF6/EIJ6I/HKc5e08rtfoLcqVxJCXptru5AUP6cv0BC9Zz+eeyrYc0dYHGeiKOvRnFcDxU8Gs85akpYzkoU/gNYmPz0Nli3CkitU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=ixjSigY9; arc=none smtp.client-ip=198.175.65.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="ixjSigY9" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1769582328; x=1801118328; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=01udh5m7XfU/YSuKGZba1QVK13n4mcDm9i4gsTeixnw=; b=ixjSigY99sPKslrIx9OwBlLkCrkHhBwJ8s6tEYMLzaeKDkCYgWi+nyqG uqsAFa+qg0xpkHkDum50lvIwoce/aRIwWZBa/tN9sUpquW0k+ciYTeEf8 I75AFU7TdqgkVBdVgl+U0Fd35VVd48tMoFQGHUddhaYjPjXNWu6Vd7TjQ 3PBg5bTmy3WnYBIvCMStW6owh6gX+K04ETSPgatxObYGNEUoaKzaLDBXt P9oxekOeflVcRd+NgU87uQ0G56nkQ2l+FAuxUOlTgvnJq+dyQh8cyhZxF tM5xEwpPVBcU0HxXyz3thxgclctxMaJMz4L0REqAKgZJEwqIki2VmmfET A==; X-CSE-ConnectionGUID: SWeDq2TgRdu3Mk4402b8vA== X-CSE-MsgGUID: hPknH3YzRBygJR+2zGVyag== X-IronPort-AV: E=McAfee;i="6800,10657,11684"; a="74415691" X-IronPort-AV: E=Sophos;i="6.21,258,1763452800"; d="scan'208";a="74415691" Received: from orviesa007.jf.intel.com ([10.64.159.147]) by orvoesa107.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jan 2026 22:38:47 -0800 X-CSE-ConnectionGUID: DZTJRim7QWi4V9kCgvJv3g== X-CSE-MsgGUID: ht2Ip1f+QIeko5cTbLLV+w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,258,1763452800"; d="scan'208";a="208255381" Received: from unknown (HELO [10.238.1.231]) ([10.238.1.231]) by orviesa007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jan 2026 22:38:42 -0800 Message-ID: <28f6ab70-94c9-46c0-bd64-7688cc1604d3@linux.intel.com> Date: Wed, 28 Jan 2026 14:38:39 +0800 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 07/26] x86/virt/seamldr: Introduce a wrapper for P-SEAMLDR SEAMCALLs To: Chao Gao Cc: linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, reinette.chatre@intel.com, ira.weiny@intel.com, kai.huang@intel.com, dan.j.williams@intel.com, yilun.xu@linux.intel.com, sagis@google.com, vannapurve@google.com, paulmck@kernel.org, nik.borisov@suse.com, zhenzhong.duan@intel.com, seanjc@google.com, rick.p.edgecombe@intel.com, kas@kernel.org, dave.hansen@linux.intel.com, vishal.l.verma@intel.com, Farrah Chen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" References: <20260123145645.90444-1-chao.gao@intel.com> <20260123145645.90444-8-chao.gao@intel.com> Content-Language: en-US From: Binbin Wu In-Reply-To: <20260123145645.90444-8-chao.gao@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 1/23/2026 10:55 PM, Chao Gao wrote: > Software needs to talk with P-SEAMLDR via P-SEAMLDR SEAMCALLs. So, add a > wrapper for P-SEAMLDR SEAMCALLs. > > Save and restore the current VMCS using VMPTRST and VMPTRLD instructions > to avoid breaking KVM. Doing so is because P-SEAMLDR SEAMCALLs would > invalidate the current VMCS as documented in Intel® Trust Domain CPU > Architectural Extensions (May 2021 edition) Chapter 2.3 [1]: > > SEAMRET from the P-SEAMLDR clears the current VMCS structure pointed > to by the current-VMCS pointer. A VMM that invokes the P-SEAMLDR using > SEAMCALL must reload the current-VMCS, if required, using the VMPTRLD > instruction. > > Disable interrupts to prevent KVM code from interfering with P-SEAMLDR > SEAMCALLs. For example, if a vCPU is scheduled before the current VMCS is > restored, it may encounter an invalid current VMCS, causing its VMX > instruction to fail. Additionally, if KVM sends IPIs to invalidate a > current VMCS and the invalidation occurs right after the current VMCS is > saved, that VMCS will be reloaded after P-SEAMLDR SEAMCALLs, leading to > unexpected behavior. > > NMIs are not a problem, as the only scenario where instructions relying on > the current-VMCS are used is during guest PMI handling in KVM. This occurs > immediately after VM exits with IRQ and NMI disabled, ensuring no > interference with P-SEAMLDR SEAMCALLs. > > Signed-off-by: Chao Gao > Tested-by: Farrah Chen > Link: https://cdrdv2.intel.com/v1/dl/getContent/733582 # [1] Reviewed-by: Binbin Wu Two nits below. > --- > v2: > - don't create a new, inferior framework to save/restore VMCS > - use human-friendly language, just "current VMCS" rather than > SDM term "current-VMCS pointer" > - don't mix guard() with goto > --- > arch/x86/virt/vmx/tdx/Makefile | 1 + > arch/x86/virt/vmx/tdx/seamldr.c | 56 ++++++++++++++++++++++++++++++ > drivers/virt/coco/tdx-host/Kconfig | 10 ++++++ > 3 files changed, 67 insertions(+) > create mode 100644 arch/x86/virt/vmx/tdx/seamldr.c > > diff --git a/arch/x86/virt/vmx/tdx/Makefile b/arch/x86/virt/vmx/tdx/Makefile > index 90da47eb85ee..26aea3531c36 100644 > --- a/arch/x86/virt/vmx/tdx/Makefile > +++ b/arch/x86/virt/vmx/tdx/Makefile > @@ -1,2 +1,3 @@ > # SPDX-License-Identifier: GPL-2.0-only > obj-y += seamcall.o tdx.o > +obj-$(CONFIG_INTEL_TDX_MODULE_UPDATE) += seamldr.o > diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c > new file mode 100644 > index 000000000000..b99d73f7bb08 > --- /dev/null > +++ b/arch/x86/virt/vmx/tdx/seamldr.c > @@ -0,0 +1,56 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright(c) 2025 Intel Corporation. Update to 2026? > + * > + * Intel TDX module runtime update > + */ > +#define pr_fmt(fmt) "seamldr: " fmt > + > +#include > +#include > + > +#include "seamcall.h" > + > +static __maybe_unused int seamldr_call(u64 fn, struct tdx_module_args *args) > +{ > + unsigned long flags; > + u64 vmcs; > + int ret; > + > + if (!is_seamldr_call(fn)) > + return -EINVAL; > + > + /* > + * SEAMRET from P-SEAMLDR invalidates the current VMCS. Save/restore > + * the VMCS across P-SEAMLDR SEAMCALLs to avoid clobbering KVM state. > + * Disable interrupts as KVM is allowed to do VMREAD/VMWRITE in IRQ > + * context (but not NMI context). > + */ > + local_irq_save(flags); > + > + asm goto("1: vmptrst %0\n\t" > + _ASM_EXTABLE(1b, %l[error]) > + : "=m" (vmcs) : : "cc" : error); > + > + ret = seamldr_prerr(fn, args); > + > + /* > + * Restore the current VMCS pointer. VMPTSTR "returns" all ones if the s/VMPTSTR/VMPTRST