From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1AE931CAA6C for ; Tue, 21 Apr 2026 13:19:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776777600; cv=none; b=RHU/9NzvOUHTRKCt0ccli4P40YXIGHCODZwnXX7+uD42BpWPl7wSiuFuMFjMCzRlQKYyPxPvyHWhkvTD1G07jOKk1adcrxASXxXXcUZ8sX991/K65lZrs231inhcHi+C1ZbHtX8yhM6absmoriXs5jvb3x3p5prooqkwJc4LquU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776777600; c=relaxed/simple; bh=l5nh2tX+tG4PyQxEGrsy245Ln5RZlFhnAyXMUDP8PX4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: In-Reply-To:Content-Type:Content-Disposition; b=HHRr7B4Z5hBQRTloMShSQb4WunseTN8vsgZs7Su3y51VEYyIhfPYlYhSsYVOAl5ijMhRR4hmwcF7u9Si7J3i/jGwNugeP9ZqVupSntjXdM4NhqyUEMVuvQcE1ME67VKImeYgoOGLSypyj5I1WtO4mCcLNroLNRLaay4Ma4lQRZM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=i8UgxQ72; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="i8UgxQ72" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1776777598; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=xexzte0yTqtWkjudFGvCNSwnTYifigEpG3qwMv3/9fw=; b=i8UgxQ72fa+nIiggRyMF3RKAikNtQ9GC2WyMUhzIIkQBqZNcTEolPDZ7xO3ryYj9m42yvI FrIOj50XPdnf6sXcvd7JNiYDYXoLRUtMYeaZbHDGeUERmsa6ZWVzmyinB3Z3O8euC6ISUC XfeQEmIT9ImbFnQq/IQYA2qdP2km+mA= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-19-7EUvDMRYO5WDRD0a2p0ceA-1; Tue, 21 Apr 2026 09:19:56 -0400 X-MC-Unique: 7EUvDMRYO5WDRD0a2p0ceA-1 X-Mimecast-MFC-AGG-ID: 7EUvDMRYO5WDRD0a2p0ceA_1776777595 Received: by mail-ed1-f72.google.com with SMTP id 4fb4d7f45d1cf-66e6f1b315dso3635834a12.3 for ; Tue, 21 Apr 2026 06:19:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776777595; x=1777382395; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=xexzte0yTqtWkjudFGvCNSwnTYifigEpG3qwMv3/9fw=; b=dLJlVJD+vdEwg3S2cIXMRQIRXwAAs8CbRsPOk2dSyg5TEMQkYyZ7nilBJOrcBKekdD kd+WZWiC4xB6sO5rVKyKUMJG0p1NP3ixQpsgApOsHQUz0ZYj4OhYMf8MpWTpO3DZteh5 zP3SzRZwhU1MVHsJfDVZ8cP7rsRy055JwGpeRuJwn7bdneN/wWy7UbuFtA7oC5tmOQVp 8jE1pt3E34nMnSBsbSA4rlpAd2mMMSDGzXCOnbh/ksS69voQzkqDhbZ2+A9La8jliDR2 YKXRz+SynTyBajHHdkVlmcsp8HEon30TDv4zoXwu5jd1iVRBYTBLmM0RlUby0SOEBToj FoRA== X-Forwarded-Encrypted: i=1; AFNElJ+oNVALK+/63srgnMSkRZCf7BidWxSiValdcUvSVbnI+BXOgyfa7iSFyH5AHb5p8QyEIEtma01gqA7g/cpPqg==@lists.linux.dev X-Gm-Message-State: AOJu0YwfO4VKrCIhXNxSHnXLDeyhKZwd7CxK1JhIKHjWtZhNPP1UFdIO ctbHVeD81jGLsKkZA6CybDyHYFeGqg3838McFpk8/+RjHC1cplRF2q+CGR7/FxDTyYzMQwkn0a6 i85fqG0OUL0jannNVDmRacLQ/LQoRPo77haM+OujG1eJO6228np/B59MVV3lsNHNjjXrh X-Gm-Gg: AeBDieud5r553TRoIlGUwBwlbWqxVII9M1Tlz/f9qg/D7q8eDnGbp8MRm3CAofy8kN6 CYBvQMzdfIBWAoL25myoJn+MEk+gl6mrmM5IrITOQsEHyNUv1rfAph2gbbUvZxk2HmIc07gBdKq zMbADAWL9euFCDWF8vk9OvOwbcI7HJO48/z8JqXsiwrC4+ZqlPmKPAkl1wZuj81YHqkd4iYjV54 1CQZQFGZYO6qnaXO5JlAgG56IXh7EA0q9g9e7aJ4YqBtoqHsO/9qE37YL56POYb69NajZNTCGYm nOa9pF7768+FsqpXaD9WcD0a7kJbd1pvsRiYfWi3A/IEZfg+VFOY+kl0+pRi6GBNCy7d8xgVEUk +F33YJdcOrIzP9HrDKCnxcT0rKvLk6XCHTZKdTrGk76BUahr5VWOClw== X-Received: by 2002:a05:6402:2b9b:b0:670:8b30:a8a7 with SMTP id 4fb4d7f45d1cf-672bfc12ae6mr8152673a12.0.1776777594773; Tue, 21 Apr 2026 06:19:54 -0700 (PDT) X-Received: by 2002:a05:6402:2b9b:b0:670:8b30:a8a7 with SMTP id 4fb4d7f45d1cf-672bfc12ae6mr8152659a12.0.1776777594246; Tue, 21 Apr 2026 06:19:54 -0700 (PDT) Received: from redhat.com (IGLD-80-230-25-21.inter.net.il. [80.230.25.21]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6744dcdf29fsm2080687a12.30.2026.04.21.06.19.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Apr 2026 06:19:53 -0700 (PDT) Date: Tue, 21 Apr 2026 09:19:49 -0400 From: "Michael S. Tsirkin" To: "David Hildenbrand (Arm)" Cc: linux-kernel@vger.kernel.org, Andrew Morton , Vlastimil Babka , Brendan Jackman , Michal Hocko , Suren Baghdasaryan , Jason Wang , Andrea Arcangeli , linux-mm@kvack.org, virtualization@lists.linux.dev, Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport Subject: Re: [PATCH RFC v2 11/18] mm: skip zeroing in vma_alloc_zeroed_movable_folio for pre-zeroed pages Message-ID: <20260421091759-mutt-send-email-mst@kernel.org> References: <39c3c8e647fc4c8e3dcb5c9d12f2e29b5404e8f2.1776689093.git.mst@redhat.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: Fem095gNEh6379N8ywJ2k7l1IJcdcK3XPVXF4x-nEfo_1776777595 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Tue, Apr 21, 2026 at 12:58:11PM +0200, David Hildenbrand (Arm) wrote: > On 4/20/26 14:50, Michael S. Tsirkin wrote: > > Use vma_alloc_folio_hints() and check PGHINT_ZEROED to skip > > clear_user_highpage() when the page is already zeroed. > > > > On x86, vma_alloc_zeroed_movable_folio is overridden by a macro > > that uses __GFP_ZERO directly, so this change has no effect there. > > > > Signed-off-by: Michael S. Tsirkin > > Assisted-by: Claude:claude-opus-4-6 > > Assisted-by: cursor-agent:GPT-5.4-xhigh > > --- > > include/linux/highmem.h | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/include/linux/highmem.h b/include/linux/highmem.h > > index af03db851a1d..8bb67772c1cb 100644 > > --- a/include/linux/highmem.h > > +++ b/include/linux/highmem.h > > @@ -321,9 +321,11 @@ struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma, > > unsigned long vaddr) > > { > > struct folio *folio; > > + pghint_t hints; > > > > - folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr); > > - if (folio && user_alloc_needs_zeroing()) > > + folio = vma_alloc_folio_hints(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr, > > + &hints); > > + if (folio && user_alloc_needs_zeroing() && !(hints & PGHINT_ZEROED)) > > clear_user_highpage(&folio->page, vaddr); > > > > return folio; > > > For others reading along, the variant on your other branch: > > diff --git a/include/linux/highmem.h b/include/linux/highmem.h > index af03db851a1d9..ffa683f64f1d1 100644 > --- a/include/linux/highmem.h > +++ b/include/linux/highmem.h > @@ -320,13 +320,8 @@ static inline > struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma, > unsigned long vaddr) > { > - struct folio *folio; > - > - folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr); > - if (folio && user_alloc_needs_zeroing()) > - clear_user_highpage(&folio->page, vaddr); > - > - return folio; > + return vma_alloc_folio(GFP_HIGHUSER_MOVABLE | __GFP_ZERO, > + 0, vma, vaddr); > } > #endif > > Looks like an extremely clean interface. OK, sure. I will post that one as v3. Let me just add a changelog in the cover letter, and see what to do about balloon. > -- > Cheers, > > David