Date:   Tue, 31 Jan 2023 14:54:03 -0800
From:   Ashok Raj <ashok.raj@intel.com>
To:     Borislav Petkov <bp@alien8.de>
CC:     Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Tony Luck <tony.luck@intel.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Alison Schofield <alison.schofield@intel.com>,
        Reinette Chatre <reinette.chatre@intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Stefan Talpalaru <stefantalpalaru@yahoo.com>,
        David Woodhouse <dwmw2@infradead.org>,
        "Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
        Jonathan Corbet <corbet@lwn.net>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Peter Zilstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Andrew Cooper <Andrew.Cooper3@citrix.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Martin Pohlack <mpohlack@amazon.de>,
        "Li, Aubrey" <aubrey.li@intel.com>, Ashok Raj <ashok.raj@intel.com>
Subject: Re: [Patch v3 Part2 1/9] x86/microcode: Taint kernel only if
 microcode loading was successful
Message-ID: <Y9mcCxYK/VPB0ATM@a4bf019067fa.jf.intel.com>
References: <20230130213955.6046-1-ashok.raj@intel.com>
 <20230130213955.6046-2-ashok.raj@intel.com>
 <Y9kAlKFfdek2rq6g@zn.tnic>
 <Y9lHDWjjnqdletL3@a4bf019067fa.jf.intel.com>
 <Y9l4FdvytLqMc3jm@zn.tnic>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <Y9l4FdvytLqMc3jm@zn.tnic>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?02VLl/x3JHzR1uS2ISlUjGZtUqC5cAtWQPc4+mHX5JK2M/sqod5c6wfK4pgm?=
 =?us-ascii?Q?snjutUxs30lO/5WzUN5qZRrzoUaOsSq5ZogsoqSRzxlpbc6uO8vlQWXYUeat?=
 =?us-ascii?Q?CCATi8nY/xIuVjOigMIp40gJ/nwwSt4ClQE/s487c//AH5dF8+4X7E5VD/fS?=
 =?us-ascii?Q?L8noEyeQ33hh5FBVbkBXvcMcWNvbkxtVcZ1QGztheY8lRwl2725mXWWdR96a?=
 =?us-ascii?Q?uDiUoao28dyM82NmRjObU9DKcb19mnhJ3evlfzp1QaDrDDe/sqOSp422qT7N?=
 =?us-ascii?Q?TrNlVie7S34xWPPGm8fj2HzP0bWY8nkfVvgveqo5nQa6Gy8NHS7JIUNH8mCF?=
 =?us-ascii?Q?lk/IqADrf/ARW4eoh6LaCoV5O1TY84ACOa8hQJ+ktjb2JpqXCo6bBvTShVhy?=
 =?us-ascii?Q?9iLJ60IwD9S9lgnTG5jIsooMBknOjrALAO7TnEDe+eQcjIz00XXzJe/3DVCZ?=
 =?us-ascii?Q?vVt6+HH7vBXWrvqht6AVXD7a7SMe2PD75dTn+wh8c+sewzQ8maBPx5DlWX8c?=
 =?us-ascii?Q?ln015PaQlHzPJ6RQyLDqn+U9FYPhQ9VXyz2Ol+HCSPgaZK5hO5+W63oDaQmf?=
 =?us-ascii?Q?PmBfVOpHmki5CCHPr7ZfWRln3Ee/Y1w4aoNL9HTLYJy+D59ycMyphoCW+rZV?=
 =?us-ascii?Q?8Fjc47cVsOUwSTCjFO0HCeXb1K/Apau4gzyuzILv31+vk5zG4Of8kiA0U9Wl?=
 =?us-ascii?Q?9f/wiH3jb6zGnyE0S05/RITCb9/rDa8L1gC+TeolLm/HCm2CodydGmNNxl7k?=
 =?us-ascii?Q?ZRoMErNH9D5MWeUicrWw3rlYn2bHzU3jQEci0XiLmuypzScUwPhwdzUk1yEt?=
 =?us-ascii?Q?t68IPRgpR7KTGhadhC1TZWJn0qA0LgIA6KEIt4qq+1XutFmbL+3bqu0K3DBh?=
 =?us-ascii?Q?rlhQMts60dczM22HRYJ6hD51lwA4QVIXdWD2qfg+RkMIFBHl1w04SWq3DkB5?=
 =?us-ascii?Q?E83MY4NuIzr90qckvQ7A+aroAEPt9opkptkwop/M1yuTy9lot175L8ujLfyY?=
 =?us-ascii?Q?SqfG/fUguEYO3beN8KF/72XDgrcL59FPma3fLa+zZVHIZrDVfScFnFLKCr7K?=
 =?us-ascii?Q?Yucx8gRJc98uqLmUiC2tWxym7gVkOShCvlXfvsqQ420tr6bYwGRG5EG5ZzKM?=
 =?us-ascii?Q?RJCmnnIfqT0Ik+c2NrlRyC5xROnauktx9z83Sl8/9dLMkTU6B7jARO1fToBV?=
 =?us-ascii?Q?k2Eunu7RePgNRjuSOI7G81iw0zMwaP4Wl1Af039xTelAfkHKhYOWXpAjRY4K?=
 =?us-ascii?Q?tRSHq5OQvusITUb+yDORPwryGd2jaaq6BLfFa5sPm7/3evAioduF+3Rnx48/?=
 =?us-ascii?Q?wluZoWjdwaB+raqQwjO1ZJC43cEem5D2LkCpGciWwBiiM/IGJZmNj/T9V9oM?=
 =?us-ascii?Q?mY7SC8S0K0M78qBjPGzrvISjdr+5IY9nOE+tJ9ukvqaWb4TomNaQ8JM4VBhs?=
 =?us-ascii?Q?LI3SKmR9j3283yOYIAbAwZV2cZYKHIa4J8kvwQc4bDOepIAOrR5WN1sBDxgs?=
 =?us-ascii?Q?SvWvTTJHXtt3nyRuykIQ54WnSada/2oUf/Bx4yATHhe08ykK0iWaL9zWjqsT?=
 =?us-ascii?Q?aVfQwq66iIx04pDHXwkFh4orV3CUYblP1Qc+Fa2x6cYJpYgIk8TYhexJX92R?=
 =?us-ascii?Q?nA=3D=3D?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 27cb75fc-30f5-4ef1-966d-08db03de2033
X-MS-Exchange-CrossTenant-AuthSource: SJ1PR11MB6201.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 31 Jan 2023 22:54:36.3119
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: tC2RbWcGK8KSfmurRsJhrJf5LuB3mZ3mbNUlwEwuc/p9qNsiiVo5w5DkPOHlS6DXAj/OMJLlaVyGYcC+OUUUzA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR11MB6768
X-OriginatorOrg: intel.com
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Jan 31, 2023 at 09:20:37PM +0100, Borislav Petkov wrote:
> On Tue, Jan 31, 2023 at 08:51:25AM -0800, Ashok Raj wrote:
> > remove ret = 0 during initialization since its cleared right below. (tglx)
> 
> Sure.
> 
> > Need to set ret explicitly to either -EINVAL, or size. Otherwise it will be
> > endlessly waiting for write to complete. (As Aubrey pointed out)
> 
> Then do:
> 
>         tmp_ret = microcode_ops->request_microcode_fw(bsp, &microcode_pdev->dev);
>         if (tmp_ret != UCODE_NEW)
>                 return size;
> 
> to signal what it is. It certainly ain't an error if it doesn't find new
> microcode.

It's not an error, only when request_microcode() returns UCODE_ERROR, should
it return -EINVAL, if its UCODE_NFOUND, or otherwise the code should treat
as success. 

The diff I attached was: https://lore.kernel.org/lkml/Y9lHDWjjnqdletL3@a4bf019067fa.jf.intel.com/

 	if (tmp_ret != UCODE_NEW)
-		return ret;
+		return (tmp_ret == UCODE_ERROR ? -EINVAL : size);

Does the above look fine? 

> 
> > I think its safe to leave ret as is, since microcode_reload_late() only
> > returns -1, or 0.
> 
> No it doesn't. Hint: stop_machine_cpuslocked().
> 
> > Pull this into the ret == 0, so taint only if the update was successful? 
> 
> Ok.
> 
> > And add a message so its not silent?
> 
> You'd add a printk for every possible operation, wouldn't you?

:-) Not like that.. But looking through most of the cases that does
add_taint() either have some print, or there some big spalt message around
it.

This shouldn't be noisy, but if you think this isn't needed, it can go
away.

> 
> See, the world doesn't revolve around microcode loading. If that thing
> fails, then someone has done a bad job at the CPU vendor testing,
> provided the code does the right thing.
> 

When it fails due to current_rev < min_rev, Isn't it good to add indication
to user space that it didn't succeed? Thomas wanted these return codes, so
someone scripting can get a status after an attempt to load.

Otherwise agree, it shouldn't generally fail.