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, 14 Aug 2023 15:44:54 +0800
From:   Yan Zhao <yan.y.zhao@intel.com>
To:     Sean Christopherson <seanjc@google.com>,
        bibo mao <maobibo@loongson.cn>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>, <kvm@vger.kernel.org>,
        <pbonzini@redhat.com>, <mike.kravetz@oracle.com>,
        <apopple@nvidia.com>, <jgg@nvidia.com>, <rppt@kernel.org>,
        <akpm@linux-foundation.org>, <kevin.tian@intel.com>,
        <david@redhat.com>
Subject: Re: [RFC PATCH v2 5/5] KVM: Unmap pages only when it's indeed
 protected for NUMA migration
Message-ID: <ZNnbdlKb6Y4L4vMx@yzhao56-desk.sh.intel.com>
Reply-To: Yan Zhao <yan.y.zhao@intel.com>
References: <20230810085636.25914-1-yan.y.zhao@intel.com>
 <20230810090218.26244-1-yan.y.zhao@intel.com>
 <277ee023-dc94-6c23-20b2-7deba641f1b1@loongson.cn>
 <ZNWu2YCxy2FQBl4z@yzhao56-desk.sh.intel.com>
 <e7032573-9717-b1b9-7335-cbb0da12cd2a@loongson.cn>
 <ZNXq9M/WqjEkfi3x@yzhao56-desk.sh.intel.com>
 <ZNZshVZI5bRq4mZQ@google.com>
 <ZNnPF4W26ZbAyGto@yzhao56-desk.sh.intel.com>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <ZNnPF4W26ZbAyGto@yzhao56-desk.sh.intel.com>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?dh+bCkXevfxNjjzdFjTgIzUXge8qD3LFncRZGd16hHCpX3DZjOr692wI+JRk?=
 =?us-ascii?Q?KcbGkevDKQHwBjOJJ3ODAUFcX9XWMijDY+gD4GXMQy3KcURdG4lVnpHwLQRB?=
 =?us-ascii?Q?xtHSQmowDmLtOGpYmqeTS6Oi3E3WRxQIkKtcEvZVauCcUcp0ZUmRaK6h2/Ne?=
 =?us-ascii?Q?OpxpqaEbGASyOoVG5lNIiFMYVX08dPGoMvGjTYw8r+bCYXLc/6otq5TD1ugD?=
 =?us-ascii?Q?TeZN2GJAksoEcwMVC8iqs00NJFpWtLstJLjEUMcYSBxyAU+qQBJ0S1+oRQIG?=
 =?us-ascii?Q?gZ186SKjafmDGhzDXAFyFWOvWRho8FkQh8cBu8NOgwE1D3lG23/J68+lkBId?=
 =?us-ascii?Q?3OLs0dWWU3TIERZe6Syi992N87r2hBGKCw2nr9cB9MJYz6b98oSkySTWG+IC?=
 =?us-ascii?Q?cP0w39tdwcdGeVNOfdhrpSzls31XmyVE4cFN7Oj1Xa5rkkFPDbiGMVF1dE0/?=
 =?us-ascii?Q?A0EM9pctBh10PkIiffFQdW7O3Lv1kcd2o6XKh12/fPwx1CvYV+p2Gf+gbRY7?=
 =?us-ascii?Q?Zr9We97db+RGpLRTfv87Diywp5z8Bk/dbnHu35c9GwBdWsreLDSa+eA8omp1?=
 =?us-ascii?Q?KnomGIjgeeDjgkRlre+Y8aOUUbkNkiTfGG+E81q9Tdag4A3/Hj81uPt0kM8h?=
 =?us-ascii?Q?0eLldjGrfD/4lhe7Otp0jUyW41qd5mBB+tHGx1QA6rmnORPmCYLt0UinG4gS?=
 =?us-ascii?Q?xR8G7XZf2Sqkt26IzSN+zN2tOFjsJiwjanOo5toMI8xrNqEA210uDMY1xqeq?=
 =?us-ascii?Q?5PPqmfonWFiyaqZOWeAsV0ubSnXH2zl9ztae8U0XFsltDJZzDacKDVe2F4AO?=
 =?us-ascii?Q?zv+QuJYjEsGh7u0950GqXjTN9iWr6it5JmvnC2hoBTRQAy8Kq4fheKZ9+lGD?=
 =?us-ascii?Q?F6iYA93Ioh6G7S3Xlqxdk1Q8RUE/lTsScfnzhofWe49J4fwtAH5H0fXy5XD9?=
 =?us-ascii?Q?3TGLfKFeaEqhZYD9kuwqWIEMsLycraBYXq3hLDlYBSoQmmBY1Kawsnj264mL?=
 =?us-ascii?Q?pxLPmcfNSkb+Wzta5ZXGV9gMF81BBc+y64APwihjUXZ4BEmcOlKnEwHgWEkx?=
 =?us-ascii?Q?Eq9tKrCTv8qLgy6r7puwyMdLCHHjP1AQ5tCjfoGDtA6JV7Epnu+YdVPT6M9I?=
 =?us-ascii?Q?nVcEXpVCLAaMdpezCLdt1M5dNIuR94mrbCDpdsWHClSg96EA4QTTTQKYAQTQ?=
 =?us-ascii?Q?biRgog0RsMufCwzlPTxFo5dxQ2JlX7gD7lp0bLXyrTkH/fq0bglZBR0QK/GY?=
 =?us-ascii?Q?mhRllGMn1l1QHqfQ79jesTLf+FdCtYeDAicEqpBy/1IS4ZvGFb+OybO2CQl5?=
 =?us-ascii?Q?KFAMECrs16AGtH6uR0f09k6Xv8ey+lCQBu9z6mUwWypbxJA6Wm1MlxVQAJLo?=
 =?us-ascii?Q?LQXaGCGyn8kagPD4lsoPizlxc2tyFvRyz6Squa1Zz/XuONc1raHafcmD3N0Z?=
 =?us-ascii?Q?GgDynlOmTsMmzIXo3R68BZa3J0/zA38x0ZzTL9s68GV1MZpSpXeUijN4fbMx?=
 =?us-ascii?Q?BAJWYw1+QrCeUkzGYUQNlyh7IGUARVTPHIGMiA5imokML6T1U9ZlkVXdDBGH?=
 =?us-ascii?Q?d9HDwTJVPHOIm3y4jbWmh8P5AHAbWTxWwPiwsl9r?=
X-MS-Exchange-CrossTenant-Network-Message-Id: e39d5f31-95ac-4a4e-3957-08db9c9e2023
X-MS-Exchange-CrossTenant-AuthSource: DS7PR11MB5966.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Aug 2023 08:11:56.3475
 (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: ZfQ5g2AcwzcZQA/U0p6JsXfWYRAiuWfhI2CV5EOBLnWNXFY3KCK90eGoe+5E74Az9TpEEHspPqwfrF0UpsMjjA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR11MB7533
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,
        RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,
        SPF_HELO_NONE,SPF_NONE 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

On Mon, Aug 14, 2023 at 02:52:07PM +0800, Yan Zhao wrote:
> I wonder if we could loose the frequency to check for rescheduling in
> tdp_mmu_iter_cond_resched() if the zap range is wide, e.g.
> 
> if (iter->next_last_level_gfn ==
>     iter->yielded_gfn + KVM_PAGES_PER_HPAGE(PG_LEVEL_2M))
> 	return false;
Correct:

@@ -712,7 +713,8 @@ static inline bool __must_check tdp_mmu_iter_cond_resched(struct kvm *kvm,
        WARN_ON(iter->yielded);

        /* Ensure forward progress has been made before yielding. */
-       if (iter->next_last_level_gfn == iter->yielded_gfn)
+       if (iter->next_last_level_gfn >= iter->yielded_gfn &&
+          iter->next_last_level_gfn < iter->yielded_gfn + KVM_PAGES_PER_HPAGE(PG_LEVEL_2M))
                return false;

        if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) {


This can reduce kvm_flush_remote_tlbs() a lot in one kvm_unmap_gfn_range() in KVM x86 TDP MMU.