Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 8 Sep 2022 14:10:00 -0700
From:   Dan Williams <dan.j.williams@intel.com>
To:     "Jonathan Zhang (Infra)" <jonzhang@fb.com>,
        Robert Richter <rrichter@amd.com>
CC:     Alison Schofield <alison.schofield@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Ben Widawsky <bwidawsk@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        "linux-cxl@vger.kernel.org" <linux-cxl@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Len Brown <lenb@kernel.org>
Subject: Re: [PATCH 09/15] cxl/acpi: Determine PCI host bridge's ACPI UID
Message-ID: <631a5a27f22ac_166f29479@dwillia2-xfh.jf.intel.com.notmuch>
References: <20220831081603.3415-1-rrichter@amd.com>
 <20220831081603.3415-10-rrichter@amd.com>
 <DE840F3C-0CBA-49A5-B9B9-9D279FFAAFFA@fb.com>
Content-Type: text/plain; charset="utf-8"
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <DE840F3C-0CBA-49A5-B9B9-9D279FFAAFFA@fb.com>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?cDJ2dDVhY3FJRzRFcFpXOHlPdGJHZU5rQVJVTi9SSHhiUXpuWEJubGk2UUlu?=
 =?utf-8?B?b202NXJ6ZjRpSUFVODRxUTR2bytyRHUyYTBxZVFpb3l3TzdFaUQ3dE5TMXR2?=
 =?utf-8?B?Sy9ZeHFMU1N5QmF5V0tSMjlxSXB6QnNDdEZzREFSelBud0l3WDdTOTEwaS9n?=
 =?utf-8?B?L1RlYnJLeldIbWlxNE9sK25FZVZseHhKTkl5S2FWaU1za1F1OFE5RmdxSEIy?=
 =?utf-8?B?SFpwUXNWVTFJc1RKaVIzaWE5ZncvNUIrL2JXaHpYYXJkV2Z2WjBtRGE3UVk4?=
 =?utf-8?B?RlRpdjJZUGZWK3VvOVFFSEFxRDM1dmMwR1I4dXhtdDZlSlhDL0NzQTI3cHNt?=
 =?utf-8?B?SzBRZDVldndxelY5eFhHZ3BoVVhSRW1qVlltcDdHL0pUdXV2R09VTWZYbEVy?=
 =?utf-8?B?VDZ2RkNkaHZYSUg1L3VQV29HazhscldBa2RqcXZCOG83eFhiQUM5djhqb2JF?=
 =?utf-8?B?WEFJUWtMOEs5dlFlVGFFdjMzUW9mbEt0bUx4OVZmdGxqU1dKTFY5MHNtMnp0?=
 =?utf-8?B?YlM4RE01c01xR0hPUVJJOHN1Rmsva3pOQVpJT3FJL0h4NERJTGYrVWFwaGk1?=
 =?utf-8?B?QndmSjNYQjNRa3RIT0Q5MWtJM0Z4NnJCZXczNTdvRUhzR0tEQllMQU85QUVn?=
 =?utf-8?B?OVFscFdZR2x3UEhzRjRDalpqMng1VkY4WnBoZGZvdUVmd1owaVNQVEYvMy8v?=
 =?utf-8?B?OCtQaVF5WVhpNk1UMXdWcTZzTW1HbzB0S3FtMS9rMks3U2VlSUFGTFV6Tkh1?=
 =?utf-8?B?a1B2NXlqZ204WnBGbWR5MkgvaW1LOExHTk5GaURDVlJlSGl4a0poQksvSVd6?=
 =?utf-8?B?OGorY1I5SzRTdzQrbGUzYitWVm1OWm9ONlhZdUdFbU1aTzNxeG95bmxyNXNO?=
 =?utf-8?B?OGRkeDcxQTlWU1dhME1Wd2ZLalIrQ29RU1dwdW9RYmZKM0JlUXJKV3AxYXVh?=
 =?utf-8?B?SzVPQUgwekNHSi9RbFc3WGUrM25BQzMvT0wwSWF2bHIwR1ZmNWNIdGZzaXpp?=
 =?utf-8?B?YkNudkdSdURRK3lydmx6S29EOCtDNDNTMXEvTnNqVVNOcXBDbmVLcTg4YkdC?=
 =?utf-8?B?L2k5Snd4cFU2SkkxRTZaSVFpTHZSNzRIN0tSQWFBeHl6L2o0anF3aDVld0Ew?=
 =?utf-8?B?cHhIcXNLM282QWYzVi92b0lxL01iQ1NmdE9WNXJSY2o1TnU5SDBVVlBzS21N?=
 =?utf-8?B?K1pldWF0ZER1ZFNnL1V0a3lmMk44bnNXM0l3amttWDJTZC9kUzNZODl0V3RM?=
 =?utf-8?B?MkFVeXlQei9QTlpyOWJ4WU1Ld0hlYzNPb0haWlpMdU1NOVJwRnhNK1JTbGhr?=
 =?utf-8?B?SHEwOWR3UTh4bURxUXkxdXRDWE9OU2U0SjN4TXFqZ2NwQzhIVmcwYSszZ1JR?=
 =?utf-8?B?azlMQW1zNGdCYmRVcnpUbUM3dGxRQVZrd3Y2cVU1SnZ3MUZQbnVscXp2dVhM?=
 =?utf-8?B?VWhTc0lEL25ETzlBRHV3R2V4MHdpUW1qN2dXNUVlZmJHYnZsdmZGK2lxdjF5?=
 =?utf-8?B?ZGJocnpsM0psc3p6eHVqRWJ0VHVVK0p3U2dBTURtQ05wQkJLUStyajJCRlhs?=
 =?utf-8?B?SDVGb2JVQk8xY2lvbzlYdHFzUlQ5aE5GU0hhL2hQbXVkQmxsa3luVGhEMGZV?=
 =?utf-8?B?Nmc4WnRkZVhmNzZoS0I2dE44VjhjZFBjVVFjRnE3RWlKVjd2QUlzUUdid3hL?=
 =?utf-8?B?NExLMzJxYkgxbjFNYWt6UTJReEpTMHVQRVNIRnU2WERSbGltNUVzUnhseEU0?=
 =?utf-8?B?eHdZREpqUzNEd284Z1RieDhaeTJra2pGK1B6TTNRTmFxdCtBMXU4em13cmNS?=
 =?utf-8?B?SGxHTWxkc1FrNzROWlgrSmZDZitUd0dLOHlnc1BRaXhNSjBjTEJYeDZRUlhC?=
 =?utf-8?B?MVZqdzFqQW5BbnJnYUtlT0RVaENNbE9yVDFZZVpBY1lLUFdUSzFickFvMXpN?=
 =?utf-8?B?MDFuVmVLYVF6V0ZYTlhDSXJ2bFdSOUxBOFBUWGNRQ2dRaHU4YkQ0cGs0cEhp?=
 =?utf-8?B?b1hnOWY4b1pBSlY0UnNTMDNtcnUzLzRrZnhsbk1LWFNQdysxY3hSL3hSQXNt?=
 =?utf-8?B?QXM1OEVYVWZpSWpYS1BDSlloY01tSWlDalQ1NnRpelMrNmRwTWYwN25GYVUx?=
 =?utf-8?B?azNadnhwWUFyMVdQNE1wcDNhOStxRnV4cVhZbko0cVQ2S3ZjbTdHMlM0Tkc5?=
 =?utf-8?B?RUE9PQ==?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 8acf2880-cd4f-401d-a233-08da91de7ecf
X-MS-Exchange-CrossTenant-AuthSource: MWHPR1101MB2126.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Sep 2022 21:10:02.4056
 (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: aojSmEG52rh1j2b0OQi0BXrN4zRxgiTRB5SSYhYcdzr8zD8ZEqGBG/GjyUOcevQxkknqYYkdODuoI3xa3shJbzqmzETELtC2m6zGr1JZ258=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR11MB5968
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,
        RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE,
        T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Jonathan Zhang (Infra) wrote:
> 
> 
> > On Aug 31, 2022, at 1:15 AM, Robert Richter <rrichter@amd.com> wrote:
> > 
> > The UID is needed to read the RCH's CEDT entry with the RCRB base
> > address. Determine the host's UID from its ACPI fw node.
> > 
> > Signed-off-by: Robert Richter <rrichter@amd.com>
> > ---
> > drivers/cxl/acpi.c | 12 ++++++++++++
> > 1 file changed, 12 insertions(+)
> > 
> > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> > index f9cdf23a91a8..b3146b7ae922 100644
> > --- a/drivers/cxl/acpi.c
> > +++ b/drivers/cxl/acpi.c
> > @@ -368,8 +368,20 @@ struct pci_host_bridge *cxl_find_next_rch(struct pci_host_bridge *host)
> > static int __init cxl_restricted_host_probe(struct platform_device *pdev)
> > {
> > 	struct pci_host_bridge *host = NULL;
> > +	struct acpi_device *adev;
> > +	unsigned long long uid = ~0;
> > 
> > 	while ((host = cxl_find_next_rch(host)) != NULL) {
> > +		adev = ACPI_COMPANION(&host->dev);
> > +		if (!adev || !adev->pnp.unique_id ||
> > +			(kstrtoull(adev->pnp.unique_id, 10, &uid) < 0))
> The UID field holds 4 bytes of ASCII characters. kstrtoull() would fail
> if the UID field has value such as ‘CX03’.

The UID field is not 4 ASCII characters.

We went through this before in the original code in
drivers/cxl/acpi.c::add_host_bridge_dport().

The CEDT.CHBS defines _UID as an integer so use acpi_evaluate_integer()
to retrieve the UID to perform the comparison. I thought there was an
errata filed to clarify this, but it seems the current spec still just
says "value". The CFMWS also places _UID values in the target list,
those are also handled as integers.