From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.19]) (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 84D16385D76; Fri, 12 Jun 2026 14:25:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.19 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781274312; cv=none; b=uxkDXdCNsHL21zjK9nFMJvVNx6BnQv7t002HiiNNtDgtZ2MighWO4Lhv7FkOwSvFyruRdkH3wh/+Tgg5YvAv0En0kDFaEo3WVgYtatd2YPuRTtFkf59IYxYgqSRd6/3xAmhXCt58vL6lSIp1Ft616jPMAOZUH0f95v8Njv9Z3V4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781274312; c=relaxed/simple; bh=yWDIQ525CsCrGba842/ZiC36lT56EmiAWt4deOpVL6Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=TerLuEpKq3K1rK8mHmw+9pr/fS6iHNoV66xTexZzsjMqqpVignbzCeBR8c6ZMua7oyQvIvSNDJkAr7RJR89SuPoreo0OZf7CKXuzwGpxp5qVv4K2rbek89YvjPOOdCailybJyJUun3KoScKcvr8aTmT6rYh39faG6K7nXsTCv7E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Sz76rST/; arc=none smtp.client-ip=192.198.163.19 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Sz76rST/" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1781274309; x=1812810309; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=yWDIQ525CsCrGba842/ZiC36lT56EmiAWt4deOpVL6Y=; b=Sz76rST/AAjmIVwDbLEWtCcjdm6dy1Jzo0YQnIGwwc89+68QK2U/YjWR TbqMXnQpEx0CYuXYN3x4kdsWYJAtFpQQeMIVOTEX477iNY8BwHP7d2d6E rbLNGLg0KddvVOcER5C5uKNPgz4ZA/256VbYajFDBvxAK5I+4TmAh98Te 6zTSYL9PiUJ0FODHWVZLQpIM/e5x77HNSjiMcKav5j8SEbVIJNGxgX0Lx q0JJUNOMjTLCiFGNYae90SlDCeOU2YOt5BaHLnLZ9cYLf6Z5PSeP4HqpX zeC6TVCGScy59CWzbp7bga1iUxIYZ7NC6dFX4/fPNkwjHZttWbTR+T+8A w==; X-CSE-ConnectionGUID: D994XSUNRU+cY+KywyUVaw== X-CSE-MsgGUID: D4XiI9ZLSD24EknMrjTBSw== X-IronPort-AV: E=McAfee;i="6800,10657,11813"; a="81116101" X-IronPort-AV: E=Sophos;i="6.24,200,1774335600"; d="scan'208";a="81116101" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by fmvoesa113.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jun 2026 07:25:09 -0700 X-CSE-ConnectionGUID: +a8NPcjIRDO8RZkcFNkx7w== X-CSE-MsgGUID: 2vFqB7OMQQWGST3/MQ7/ZQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.24,200,1774335600"; d="scan'208";a="243902245" Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.124.240.18]) ([10.124.240.18]) by fmviesa007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jun 2026 07:25:06 -0700 Message-ID: <49728a57-a996-470d-92b7-209a010b4761@intel.com> Date: Fri, 12 Jun 2026 22:25:03 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] x86/tdx: Add helper to query maximum TD Quote size To: Peter Fang , Dave Hansen , Kiryl Shutsemau , Rick Edgecombe , Kuppuswamy Sathyanarayanan Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org References: <20260612110853.3188196-1-peter.fang@intel.com> <20260612110853.3188196-2-peter.fang@intel.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: <20260612110853.3188196-2-peter.fang@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/12/2026 7:08 PM, Peter Fang wrote: > TDX attestation blob ("TD Quote") sizes can grow with newer > cryptographic schemes, so guests can no longer rely on a fixed-size > buffer for the Quote. > > Newer TDX modules report the maximum TD Quote size via a TD-scope > metadata field. Add a helper to query it instead of exposing tdg_vm_rd() > directly, as it can read arbitrary metadata fields. > > Thanks to Xu Yilun for suggesting this. > > Assisted-by: Claude:claude-opus-4-7 > Assisted-by: GitHub Copilot:gpt-5.4 > Signed-off-by: Peter Fang Reviewed-by: Xiaoyao Li I have another nit other than Kiryl's > --- > arch/x86/coco/tdx/tdx.c | 19 +++++++++++++++++++ > arch/x86/include/asm/shared/tdx.h | 1 + > arch/x86/include/asm/tdx.h | 2 ++ > 3 files changed, 22 insertions(+) > > diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c > index 186915a17c50..88c66c46e70a 100644 > --- a/arch/x86/coco/tdx/tdx.c > +++ b/arch/x86/coco/tdx/tdx.c > @@ -197,6 +197,25 @@ u64 tdx_hcall_get_quote(u8 *buf, size_t size) > } > EXPORT_SYMBOL_GPL(tdx_hcall_get_quote); > > +/** > + * tdx_get_max_quote_size() - Get the maximum TD Quote size > + * > + * Read the maximum size of a TD Quote from a 4-byte TD metadata field. The TDX > + * guest driver uses it to size the buffer for Quote retrieval. Older TDX > + * modules do not support this field and return an error. > + * > + * Return: Maximum Quote size in bytes on success, or 0 on failure. > + */ > +u32 tdx_get_max_quote_size(void) > +{ > + u64 val, ret; > + > + ret = tdg_vm_rd(TDCS_QUOTE_MAX_SIZE, &val); > + > + return ret ? 0 : (u32)val; > +} > +EXPORT_SYMBOL_GPL(tdx_get_max_quote_size); Do we need to start to use EXPORT_SYMBOL_FOR_MODULES(tdx_get_max_quote_size, "tdx-guest") ? > + > static void __noreturn tdx_panic(const char *msg) > { > struct tdx_module_args args = { > diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h > index 049638e3da74..2880f493a8e5 100644 > --- a/arch/x86/include/asm/shared/tdx.h > +++ b/arch/x86/include/asm/shared/tdx.h > @@ -49,6 +49,7 @@ > /* TDX TD-Scope Metadata. To be used by TDG.VM.WR and TDG.VM.RD */ > #define TDCS_CONFIG_FLAGS 0x1110000300000016 > #define TDCS_TD_CTLS 0x1110000300000017 > +#define TDCS_QUOTE_MAX_SIZE 0x9010000200000008 > #define TDCS_NOTIFY_ENABLES 0x9100000000000010 > #define TDCS_TOPOLOGY_ENUM_CONFIGURED 0x9100000000000019 > > diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h > index a149740b24e8..ac39674c9479 100644 > --- a/arch/x86/include/asm/tdx.h > +++ b/arch/x86/include/asm/tdx.h > @@ -72,6 +72,8 @@ int tdx_mcall_extend_rtmr(u8 index, u8 *data); > > u64 tdx_hcall_get_quote(u8 *buf, size_t size); > > +u32 tdx_get_max_quote_size(void); > + > void __init tdx_dump_attributes(u64 td_attr); > void __init tdx_dump_td_ctls(u64 td_ctls); >