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:   Mon, 29 Aug 2022 16:02:22 -0700
From:   Dan Williams <dan.j.williams@intel.com>
To:     Davidlohr Bueso <dave@stgolabs.net>, <dan.j.williams@intel.com>
CC:     <x86@kernel.org>, <nvdimm@lists.linux.dev>,
        <linux-cxl@vger.kernel.org>, <peterz@infradead.org>,
        <bp@alien8.de>, <akpm@linux-foundation.org>,
        <dave.jiang@intel.com>, <Jonathan.Cameron@huawei.com>,
        <vishal.l.verma@intel.com>, <ira.weiny@intel.com>,
        <a.manzanares@samsung.com>, <linux-kernel@vger.kernel.org>,
        <dave@stgolabs.net>, <hch@lst.de>
Subject: RE: [PATCH -next] memregion: Add arch_flush_memregion() interface
Message-ID: <630d457ee7739_259e5b29444@dwillia2-xfh.jf.intel.com.notmuch>
References: <20220829212918.4039240-1-dave@stgolabs.net>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20220829212918.4039240-1-dave@stgolabs.net>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?0TAWkamx5b9hvbVljUMe9HmPuSZqoc3woN+DrEpcGHx9FSU2Svan9DUGPHjF?=
 =?us-ascii?Q?BjgsV5yM/aCOwCy0cXrA1ydOs7NNesCGPLDhgqMCR4Opyed7Q7srhXgJQtA8?=
 =?us-ascii?Q?ZQ9NYOo1ZoAQbtRkDnOiKFbaxRlwSIE4HJgKMRiV3gt72qsCwnpg7Zd2x+mH?=
 =?us-ascii?Q?hEtPOZgsWqnYjI21cLZEDC2v8lbwBqJ3OaY4tCKQhIEGC1qpQI8xRK8Q0G6G?=
 =?us-ascii?Q?Cuf81SiQTVr6+4sbE6CsUyX34kQXFnn0XZRNaxug0fIp3DqMmoJdR7OU5oP6?=
 =?us-ascii?Q?idCsIGw3opNbZYuWNp1DsG2s3KFBE/51vXDix9T7v2KMVOwVKBmoacdEwE/1?=
 =?us-ascii?Q?C7m5jWVdao+N9l3Tp56XDmMzWSKpklJno8Nt+/DLTSiptrxahSQ4S8hVDkzK?=
 =?us-ascii?Q?skp/oEiHq5uDnA9vj1t4mZ75xgQp8XUoQB8BdqJYaT/uO4agNK87aisCr1fQ?=
 =?us-ascii?Q?SRX9RXVPO45+UBIXxyehjkeIjBitdaD4JybKxq4yWsxJuLGPbSzhqy3YH3DU?=
 =?us-ascii?Q?Xq9nkLXpU8bXB1chP5oHjpyG8PiSuhqI7TvUWQNhYkbwFBhOAapTJuSbfzXv?=
 =?us-ascii?Q?FP1vA26Y8ye+vLCTRB2YZPlVh8c4wXDKCh031hlcJfnHsxnDNot8BIs1KXFq?=
 =?us-ascii?Q?JW7knzt1aZfXIi2h9Mz79hNQAGCbW724Urc+IP/kHk36Lw3ZOefmvOI2VUi5?=
 =?us-ascii?Q?aBvU9UdSTrFrog2KZDybJKuNCzZ9/umRuRlIu8tBxrCBlEO/mBrj1uQB8llc?=
 =?us-ascii?Q?wNE32uBTce0U80q975IpzSgvEX85hOaAX9xr9oGj+usnYNw+VBTxqJMrNy/z?=
 =?us-ascii?Q?gSRImlITiYeChIfpazeD0LNaivNYfVG5D5Q4hM8v/44ZWfv8Q+lLHcrawM59?=
 =?us-ascii?Q?Kej/ZkykgMjsb9Yy5n/1RmRBCIzLBrKH4hZ0ia589aNKkTL0Jj5KJgQEBovr?=
 =?us-ascii?Q?NDybDHTEnvozNawl6JPMp6hbKCgCd1DHkAHI2g5BldwwAfoDWFCI5QRPjs5y?=
 =?us-ascii?Q?AeJ2fjP5O60XWcf0fb6RRi1FKcOgDCxz7jHj4duqOD5/DkEwSB2+g3DiZuDC?=
 =?us-ascii?Q?GLvdnThaZJFO+gVoCLpLsQ55WM84r0zcGaG/07FnyXityynN7EhF2J8FD533?=
 =?us-ascii?Q?toCZrOhHg/k9fagzjRn7CRu9j6SLtrv79tOwHIsIow7XjyIFA95J9TsHlY0z?=
 =?us-ascii?Q?XN477CSrRJikuqUesYYbN7CHbLnWisBIX16Zd0XG0+a7zps+cBu6yGhH8Vdl?=
 =?us-ascii?Q?L9/+BPho7khYAb63y6VgOhE/D4RncRQFNQn1a0rwYbwzKxafzMou7z/tKqSd?=
 =?us-ascii?Q?I6p87H7mTAl8RicWxnlf+8dbugEp51DYj0Alq7049THiuVpStFG5+BLGOOU/?=
 =?us-ascii?Q?xV6BUmknLuAbUIobiAiQcUwl2wwwmr6us+9knps7frZUJK6uKQ2B/NHyMKiJ?=
 =?us-ascii?Q?nB0bJ4+iQrmcVRAWOtVuuL2xWsUmYqYygVaAQ/m7b/nDfUYWqMHkeViYCEY9?=
 =?us-ascii?Q?UwRU2QQa/edUt0NwaYxhl1w2bN6QuEbH5sgzdfPhVXE2guds8+O4ONB1K1M+?=
 =?us-ascii?Q?jQuSqbT1PR1EVHNoaJHljk8qZpCmT00ybfxu2NLzEr8gzLuV6s5xuMu0vv7u?=
 =?us-ascii?Q?ZQ=3D=3D?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 7a58cab4-22f0-4a4f-e333-08da8a1289eb
X-MS-Exchange-CrossTenant-AuthSource: MWHPR1101MB2126.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Aug 2022 23:02:25.6203
 (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: 97OO0aTeKBWd55yTltPsCosk8pCrnhENVure6d90LalHYV508HTL5mjyO2WDjwWWPNRlKzxWldNP7MG8zhdkm0u6JaoBVFWg+tCoMWrJcis=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR1101MB2287
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

[ add Christoph ]

Davidlohr Bueso wrote:
> With CXL security features, global CPU cache flushing nvdimm requirements
> are no longer specific to that subsystem, even beyond the scope of
> security_ops. CXL will need such semantics for features not necessarily
> limited to persistent memory.
> 
> The functionality this is enabling is to be able to instantaneously
> secure erase potentially terabytes of memory at once and the kernel
> needs to be sure that none of the data from before the secure is still
> present in the cache. It is also used when unlocking a memory device
> where speculative reads and firmware accesses could have cached poison
> from before the device was unlocked.
> 
> This capability is typically only used once per-boot (for unlock), or
> once per bare metal provisioning event (secure erase), like when handing
> off the system to another tenant or decommissioning a device.
> 
> Users must first call arch_has_flush_memregion() to know whether this
> functionality is available on the architecture. Only enable it on x86-64
> via the wbinvd() hammer.
> 
> Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> ---
> 
> Changes from v2 (https://lore.kernel.org/all/20220819171024.1766857-1-dave@stgolabs.net/):
> - Redid to use memregion based interfaces + VMM check on x86 (Dan)
> - Restricted the flushing to x86-64.
> 
> Note: Since we still are dealing with a physical "range" at this level,
> added the spa range for nfit even though this is unused.

Looks reasonable to me.

Reviewed-by: Dan Williams <dan.j.williams@intel.com>