From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F03F3C55172 for ; Sat, 1 Aug 2026 14:43:08 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.1380254.1624255 (Exim 4.92) (envelope-from ) id 1wqAv8-0005Se-Lr; Sat, 01 Aug 2026 14:42:38 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 1380254.1624255; Sat, 01 Aug 2026 14:42:38 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1wqAv8-0005SX-Ij; Sat, 01 Aug 2026 14:42:38 +0000 Received: by outflank-mailman (input) for mailman id 1380254; Sat, 01 Aug 2026 14:42:37 +0000 Received: from mx.expurgate.net ([194.145.224.20]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1wqAv6-0005SR-8R for xen-devel@lists.xenproject.org; Sat, 01 Aug 2026 14:42:37 +0000 Received: from mx.expurgate.net (helo=localhost) by mx.expurgate.net with esmtp id 1wqAv4-009QRQ-BF for xen-devel@lists.xenproject.org; Sat, 01 Aug 2026 16:42:35 +0200 Received: from [10.42.69.11] (helo=localhost) by localhost with ESMTP (eXpurgate MTA 0.9.1) (envelope-from ) id 6a6e05b7-e002-0a2a0a5209dd-0a2a450ba9c2-20 for ; Sat, 01 Aug 2026 16:42:33 +0200 Received: from [91.218.175.185] (helo=out-185.mta0.migadu.com) by tlsNG-42698a.mxtls.expurgate.net with ESMTPS (eXpurgate 4.57.1) (envelope-from ) id 6a6e05d8-b7e8-0a2a450b0019-5bdaafb99398-3 for ; Sat, 01 Aug 2026 16:42:32 +0200 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" Authentication-Results: eu.smtp.expurgate.cloud; dkim=pass header.s=key1 header.d=linux.dev header.i="@linux.dev" header.h="From:Subject:Date:Message-ID:To:Cc:MIME-Version:Content-Transfer-Encoding:In-Reply-To:References" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1785595351; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9bAGXb0quOYyJBifFj3CMsobl7Wj528s8Q4pbvQG4r8=; b=NEVhQSZZKi4DShjfGxrZuPRqNtphOqe5pi5nbT5xk6bKbRruhnX8733czhr713IWW5JtNX lBIXPePnqdQ4ryvX+Ui/oO5FEIW8RXuUpYzDAhh8N6HVjtmRQGHRB2ii5QDX7Pypq+cifn JH9gGi4r4HorTfPR/8XI8D8vS+iUZ30= From: Usama Arif To: Zi Yan Cc: Usama Arif , David Hildenbrand , "Matthew Wilcox (Oracle)" , Andrew Morton , Muchun Song , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Gregory Price , Ying Huang , Alistair Popple , Johannes Weiner , Qi Zheng , Shakeel Butt , Kairui Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , xen-devel@lists.xenproject.org Subject: Re: [PATCH RFC 03/14] xen/grant-table: stop setting PG_private on pages for grant mapping Date: Sat, 1 Aug 2026 07:42:19 -0700 Message-ID: <20260801144223.1599317-1-usama.arif@linux.dev> In-Reply-To: <20260731-remove-pg_private-v1-3-142c97ba3562@nvidia.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-purgate-ID: tlsNG-42698a/1785595353-1AEDE9EA-5B6B8159/0/0 X-purgate-type: clean X-purgate-size: 2611 On Fri, 31 Jul 2026 22:13:26 -0400 Zi Yan wrote: > gnttab_alloc_pages() stores xen_page_foreign in allocated page->private. in allocated page->private "for 32-bit only". > On 32-bit, a pointer to xen_page_foreign is stored; on 64-bit, > xen_page_foreign is stored inline. Checking page->private != NULL is enough > to tell whether a xen_page_foreign needs to be freed on 32-bit and > page->private is zeroed unconditionally on 64-bit. > > It prepares for a future commit that remove PG_private. > > No funtional change intended. > > Assisted-by: Claude:claude-opus-4-8 > Assisted-by: Codex:gpt-5 > Signed-off-by: Zi Yan > To: Juergen Gross > To: Stefano Stabellini > Cc: Oleksandr Tyshchenko > Cc: xen-devel@lists.xenproject.org > Cc: linux-kernel@vger.kernel.org > --- > drivers/xen/balloon.c | 5 +++++ > drivers/xen/grant-table.c | 7 +++---- > 2 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c > index e7f1d4ca6d753..7f47b0ad05607 100644 > --- a/drivers/xen/balloon.c > +++ b/drivers/xen/balloon.c > @@ -182,6 +182,11 @@ static struct page *balloon_retrieve(bool require_lowmem) > > __ClearPageOffline(page); > dec_node_page_state(page, NR_BALLOON_PAGES); > + /* > + * clear page->private before giving it out, since it might be used to > + * store xen_page_foreign info. > + */ > + set_page_private(page, 0); > > return page; > } > diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c > index 35f879dc5dfb8..cc348ba2e0786 100644 > --- a/drivers/xen/grant-table.c > +++ b/drivers/xen/grant-table.c > @@ -875,7 +875,7 @@ int gnttab_pages_set_private(int nr_pages, struct page **pages) > > set_page_private(pages[i], (unsigned long)foreign); > #endif > - SetPagePrivate(pages[i]); > + /* Data is stored in page->private on 64-bit */ On 64-bit arch you just iterate an empty for loop. Cleaner to put the whole for loop in ifdef? > } > > return 0; > @@ -1031,12 +1031,11 @@ void gnttab_pages_clear_private(int nr_pages, struct page **pages) > int i; > > for (i = 0; i < nr_pages; i++) { > - if (PagePrivate(pages[i])) { > #if BITS_PER_LONG < 64 > + if (page_private(pages[i])) > kfree((void *)page_private(pages[i])); > #endif > - ClearPagePrivate(pages[i]); > - } > + set_page_private(pages[i], 0); > } > } > EXPORT_SYMBOL_GPL(gnttab_pages_clear_private); > > -- > 2.53.0 > >