From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 17A36606A326 for ; Sat, 7 Nov 2026 07:02:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=bnxM9mVA; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=I3yQwc+n DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:To:References:Message-Id: Content-Transfer-Encoding:Cc:Date:In-Reply-To:From:Subject:Mime-Version: Content-Type:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=SNyW7L7svCZC+4vm04JJa3Y3COX/LWxh617gbF6SI0E=; b=bnxM9mVAOa4BBd XBlm6B45fqYl/Ka/kCzpY1TXqgEVlnVMYcYOjavZ56M6NdKcqsWIBLqHKYl+jvsO7ctWgyVz+EHae hNIn44afcqk7A6fn/oRhcWVUKqooxBGLvXMqyuTLOnG3hFDCUhJHKWFzDOqsWJdU1pcjXnAjupqnA fA1vPgvYnmiePbRTnRhEi+hPx95faC8qTEgUkNYkOo8EH+6d+P1DIdM6HHDlyNKUlZyXLKOBdftaR U0H0g/Wy/cCLu4PSWpvXvnZBX/BTqCAD6ImdwxQjm5gTeWa/qVOGAEZUXXVx3S0DxgLJrU/K4djJh FZSMEwEHRg08e3qOeClg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xPaRQ-0000000EIXs-12Mq; Sat, 07 Nov 2026 07:02:20 +0000 Received: from out-111.mta1.migadu.com ([2001:41d0:203:375::6f] helo=mta1.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xPaRN-0000000EIXS-12Ok for linux-arm-kernel@lists.infradead.org; Sat, 07 Nov 2026 07:02:18 +0000 X-Envelope-To: linux-arm-kernel@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=1eU8LB4FiA31cEPkSs3z/GNpYbcTIlce7/3o/u8t5mo=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1794034934; v=1; x=1794639734; b=I3yQwc+nnr9dZ9rJHoIeeQfQUjIaGc2f/SLqKrFxDV2I480KdIkDlwFLnBpoNmKhbVN3fUXJ 61MUGbXwbuS+9RE94YjhsGLI1nsOE0EUWlJkqkywRE5Q624MjkvGo6fGlaAjtrHSpshsbklTY2m LIEKSxp9znNWy0ITPbV6NfYw= X-Envelope-To: linux-arm-kernel@lists.infradead.org Received: by mta10.migadu.com with ESMTPS id 89d1383c0cbcfc28; Sat, 07 Nov 2026 07:02:14 +0000 X-Mizu-Trace-ID: 89d1383c0cbcfc28 X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=us-ascii X-Archived-By: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3901.200.71.1.16\)) Subject: Re: [PATCH v2 07/20] hugetlb_vmemmap: Disable HVO sysctl if arch doesn't support HVO From: Muchun Song In-Reply-To: <20261003002123.505555-8-jthoughton@google.com> Date: Sat, 7 Nov 2026 15:01:47 +0800 Cc: Will Deacon , Catalin Marinas , Oscar Salvador , Andrew Morton , Nikos Nikoleris , Linu Cherian , Mark Rutland , David Hildenbrand , Ryan Roberts , Nanyong Sun , Yu Zhao , Frank van der Linden , David Rientjes , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org Content-Transfer-Encoding: quoted-printable Message-Id: <2122761A-45AD-4AEC-AE88-B51E92E2CA40@linux.dev> References: <20261003002123.505555-1-jthoughton@google.com> <20261003002123.505555-8-jthoughton@google.com> To: James Houghton X-Mailer: Apple Mail (2.3901.200.71.1.16) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261106_230217_494005_E4916411 X-CRM114-Status: GOOD ( 23.18 ) X-Spam-Score: -2.1 (--) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" X-Spam-Status: No, score=-15.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 > On Oct 3, 2026, at 08:21, James Houghton = wrote: >=20 > Do not create the vm.hugetlb_optimize_vmemmap sysctl when the > architecture lacks support. This serves only to avoid confusion for > users. >=20 > arm64 support for HVO is conditional on certain hardware features = being > enabled for all online CPUs. By the time hugetlb_vmemmap_init() runs, > all secondary CPUs will have started, and the system feature set will > have stabilized, including HVO-through-BBM, which > arch_hugetlb_vmemmap_optimization_supported() checks for. >=20 > Signed-off-by: James Houghton > --- > mm/hugetlb_vmemmap.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) >=20 > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c > index 8596a462fee6..817ce39d4cf3 100644 > --- a/mm/hugetlb_vmemmap.c > +++ b/mm/hugetlb_vmemmap.c > @@ -763,6 +763,21 @@ static int __init hugetlb_vmemmap_init(void) > /* HUGETLB_VMEMMAP_RESERVE_SIZE should cover all used struct = pages */ > BUILD_BUG_ON(__NR_USED_SUBPAGE > HUGETLB_VMEMMAP_RESERVE_PAGES); >=20 > + /* > + * Architectures that need to probe CPU support for HVO have = done > + * such probing now. = arch_hugetlb_vmemmap_optimization_supported() > + * will return the correct value. > + */ > + if (!arch_hugetlb_vmemmap_optimization_supported()) { I'm wondering if we could put this architectural check into = hugetlb_vmemmap_optimizable(), > + if (vmemmap_optimize_enabled) > + pr_info("vmemmap optimization not supported by = hardware\n"); then, we do not need those code. If the current kernel does not support = HVO, then the sysctl does not exist. It's already a common case when the size = of struct page is not power of two. If users really want to know whether = HVO is enabled, they can check via this sysctl file. Therefore, we don't = need to print a log line. Thanks, Muchun > + /* > + * Return early to avoid setting up the hugetlb vmemmap > + * sysctls; HVO is not usable. > + */ > + return 0; > + } > + > for_each_hstate(h) { > if (hugetlb_vmemmap_optimizable(h)) { > register_sysctl_init("vm", = hugetlb_vmemmap_sysctls); > --=20 > 2.56.0.rc1.315.gc6ed9934b7-goog >=20