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Thu, 22 Oct 2026 03:52:30 +0000 X-Mizu-Trace-ID: 27a94bb973f2152f X-Migadu-Flow: FLOW_OUT From: Lance Yang To: songmuchun@bytedance.com Cc: osalvador@suse.de, akpm@linux-foundation.org, rppt@kernel.org, qi.zheng@linux.dev, lance.yang@linux.dev, jthoughton@google.com, david@kernel.org, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 02/12] mm: hugetlb_vmemmap: unify VMEMMAP_{SPLIT,REMAP}_NO_TLB_FLUSH Date: Thu, 22 Oct 2026 11:52:19 +0800 Message-ID: <20261022035219.45930-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261020115824.823278-1-songmuchun@bytedance.com> References: <20261020115824.823278-1-songmuchun@bytedance.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: AD97140008 X-Stat-Signature: i14czpzbt7xnhozny7fnkqfmbxsy3hyc X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1792641151-68673 X-HE-Meta: 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 Y++BPv5/ MzBMjRIBYyGDor6T3A9uju+hIAX2XMR1NknIF3dFHAMd2rpIlEba1UmC9subKnTIAIjFAx1nurGI4fXNYjfee2rv9IYge4EtgWqHdZ40CsiCwSOUkRq7l4epmnkLXnkryRNkpk/YnBNA45C7Zhd5gyI6IO88LnS/LA/5fxw9p+JjnDUHG8uBr8MKTjrX9g0EMr6yj/A9ssIq31z+jGOepLiPk1Qt6QthORvK+xeyyc2y85n8GwtCtW6Faje6uuYFtWIiVYRa+u9/JsUR1hO/bM7ZMu+SGSrT7DNX2zSZlzhKdmfBAPEYNrgorTg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, Oct 20, 2026 at 07:58:14PM +0800, Muchun Song wrote: >VMEMMAP_SPLIT_NO_TLB_FLUSH and VMEMMAP_REMAP_NO_TLB_FLUSH do not >describe fully independent choices. A split-only walk can defer the >PMD-split flush to a later global flush, and a remap-only walk can >defer the final remap flush. However, when a PMD split is followed >by PTE remapping, the split flush must happen before the PTEs are >changed, because stale large-page translations must not overlap with >new small-page translations that map different physical pages. > >Replace the two flags with a single VMEMMAP_REMAP_NO_TLB_FLUSH flag. >Keep split-only walks able to defer the flush, but force the split >flush whenever a remap_pte callback is present. Callers that batch >HVO work can still defer the final remap flush and issue their own >global flush. > >Current callers keep the same flushing behavior. > >Signed-off-by: Muchun Song >--- Nice work, don't really need two flags anymore :) If we're going to remap, we still flush after the PMD split, so we can keep batching the final flush :) Reviewed-by: Lance Yang