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X-CSE-ConnectionGUID: NxFr/1WRT8yIXkvMUJrXDQ== X-CSE-MsgGUID: Bn0eXUqWRZa+rAZny03zMA== X-IronPort-AV: E=McAfee;i="6700,10204,11371"; a="42741911" X-IronPort-AV: E=Sophos;i="6.14,242,1736841600"; d="scan'208";a="42741911" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by orvoesa111.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Mar 2025 09:04:24 -0700 X-CSE-ConnectionGUID: Sd/nwZmtQjGCvGi4SH4L8A== X-CSE-MsgGUID: /4TOiqpLQ+qYetFEnI7wLg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.14,242,1736841600"; d="scan'208";a="121383959" Received: from ldmartin-desk2.corp.intel.com (HELO [10.125.108.3]) ([10.125.108.3]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Mar 2025 09:04:15 -0700 Message-ID: <862e626a-3d4b-40c0-b1b1-6a51b30dcd22@intel.com> Date: Wed, 12 Mar 2025 09:04:14 -0700 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 2/2] x86/sev: Make SEV_STATUS available via SYSFS To: Joerg Roedel Cc: Joerg Roedel , x86@kernel.org, hpa@zytor.com, Tom Lendacky , Nikunj A Dadhania , Larry.Dewey@amd.com, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, Juergen Gross , kirill.shutemov@linux.intel.com, alexey.gladkov@intel.com References: <20250312144107.108451-1-joro@8bytes.org> <20250312144107.108451-3-joro@8bytes.org> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/12/25 08:07, Joerg Roedel wrote: > Hi Dave, > > On Wed, Mar 12, 2025 at 07:57:31AM -0700, Dave Hansen wrote: >> Do we really want to just plumb the raw MSR out to userspace? Users >> would still need to parse the thing, so it's not _really_ human readable. > > I agree that this is not really human readable. On the other side SYSFS > is more an interface targeted for tools than optimized for human > readability (see the one-datum-per-file rule). Right, but I think it's also intended to be independent and not *require* tools to make sense of the output. A raw MSR requires tooling or someone sitting there with the hardware docs to make sense of it. That's why we have things like: /sys/kernel/mm/transparent_hugepage/enabled that tell you: [always] madvise never as opposed to the old style in: /proc/sys/vm/zone_reclaim_mode which require you to go read the docs and figure out what 0/1/2 mean. > The actual use-case (and the reason for these patches) of the sev_status > file is to provide a better and more secure interface than /dev/msr to a > tool named snpguest. Let's draw this out to its natural conclusion. There are also a bunch of TDX attributes that tell you about the capabilities of the VM and the TDX module. Should we have: /sys/devices/system/cpu/tdx/tdx_attributes which just dumps out the raw register values that come back from the TDCALL? Then we'll go write a tdxguest tool to parse those values.