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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 70143C55172 for ; Sat, 1 Aug 2026 14:42:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3F9146B007B; Sat, 1 Aug 2026 10:42:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3CFDD6B0088; Sat, 1 Aug 2026 10:42:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 30F696B008A; Sat, 1 Aug 2026 10:42:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 0F3226B007B for ; Sat, 1 Aug 2026 10:42:37 -0400 (EDT) Received: from smtpin07.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 7D88B12032F for ; Sat, 1 Aug 2026 14:42:36 +0000 (UTC) X-FDA: 85052966712.07.E20C78E Received: from out-183.mta0.migadu.com (out-183.mta0.migadu.com [91.218.175.183]) by imf17.hostedemail.com (Postfix) with ESMTP id 65FFD4000E for ; Sat, 1 Aug 2026 14:42:34 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=NEVhQSZZ; spf=pass (imf17.hostedemail.com: domain of usama.arif@linux.dev designates 91.218.175.183 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1785595354; b=pJWDySNcIUQ8KK9ILKoBs/prU5TKG1KOOMSd/hyVYoaQG//c7+cnqhTUNKzrkR46Ft7jD4 LKXnlKrDHBn3YWNYZvYWT3P7XSGs7cFMrBrBYWCn6kMyLmj77G3P3FG0y6SLwXJjXFCNXb ZlF/IWA8u4egVqQOXuv0KxvWXJDaG+M= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=NEVhQSZZ; spf=pass (imf17.hostedemail.com: domain of usama.arif@linux.dev designates 91.218.175.183 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1785595354; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=9bAGXb0quOYyJBifFj3CMsobl7Wj528s8Q4pbvQG4r8=; b=XADjV2Izlmzw2CuecmbdSEOyUvNHzhOMh+ercKZ7whnB765ek2oFnFWkhJeXlQ5tUpLgEy Sbvy6gZHd/nF930duL7mAg4VuwyEOJf8jhivJWF97m3VOMJ6SCJY3Qqcg8VDsEKqrpaX2l iLchaaGQ8YE3pRs+F7UEK8kixivKf6Y= 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-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 65FFD4000E X-Stat-Signature: 8ta837mtwy6mc5ozt3pp3wg8nnyptbnm X-Rspam-User: X-HE-Tag: 1785595354-12082 X-HE-Meta: U2FsdGVkX1+P/qSoO2W7DdBDw7wIC+u7odxcXPXl6FSCA4SNY/jOgCz7NoXZvM1Hp1mkTwId7ANumhtreUdqbpa73Ehh6Q4UtNOLNhN54dXzbLSfw3aZMIBHN8l4PhMnf2FkW5xcbewjFpwwMDuh0+tSWcHvozupaeF8MJ+2E92uaXLPMl25fNnulm+ww92lk/41dN5f7YlmHFQrRIuA+9GJr5o0AHFMFhP0C8UMgbrXS0N6ZGpbMNKQ54A2owJ2ay916FFlJD8pvEKq9q9rneIWshbEd/6SnJm9Vy7BnMMMCxEpenfUkyq1xxXrQFRWeNd7H8nGEDiMdxwOsQZX6Jln4hCxQ/wTGskTA2zhbMTkyamp+9XC4522LyjiOsEHJQ7zZp3Sp7dXtWrnXn/X2rv+CI1i+X1WCEEUcyAKC3PXQc9slH2K7U742h8ENczjOWeYfZxSxghHc4XhuwJL2a2kExPW34eNW08zdlQ0+xIoICorbLbWqOvkHZrcfywTmOKL2DDvY4Pa1wrunObDkXD/H+0hSLWU3ZIazj4m1xYtvJ/tcpa7agtUkaTme+H4r5R+tUda6TNIztxnuzMvXHb4OSoEd5mREoHhCUwh62IKQcu6cqlc2aPhGLCXkP5R5XkAUji6EYODv1QtrDva9kGvKh5yvLJVCulinOSBM8O294wfs8lVIZuyH7QxBPV0DKvZ5czKJyf0crgKkzkIeuJckG/PkRIPDqcRrXD1iZ6w7vcIWRMo6lu65LQZjkaxHdaaFaex9CBYVCi8d7lu0GC0P1FjMMslIG0hreXDtXWECVg0gNuAvqQnyJdo5Y0uMaj4Wotc9NWhoVE67ZRxGKEB80Bz3euQHEQo/boRYqP3Fcwo7yoa6TW0BgJTkJ3ArLBFEfamOA1IFZMiIxZ3Nz41SRdzMwOmRBoAwRHHlXwSCJtKzz9dOCKVcIRLgczzQcFT6Kprcw8SKipetzE Mu7xkeJ+ 4NX/v+cALjeEOadlq9F+eaSM7tVUYZvz7RHVUdDtKY06SPSLaCO4wRBpWAlwFPTZ/7gOBR2lvJFn/pWq3KkcYWNd3FCt5YYZlWyIgXpZjI+TCpDnTFNxJh4uTDxJV2nxDVCMuEv2XZXZBUqaVBwtjgonch8c8oNeAgZ83/5yqxAtOclYPB601jIUc80Bo8etRUb/CFRBfllO6yn9IfGmsWgASAI+1h+9M64M9ojC+BeWu6ecCnJYP7bju1DpwHzRABpm47a1cAUYjLiMxV8gRNBwBKXVnYjPDVKqyC6LMbXHVxUn7jq+JZYfyBXTZTgfREHcdJsdicGtiZ2PxvxR/TWxJ3Bn1dEGEnDN7QmLY82zoFuWD3lVLIo8jPWEPjV+v83gun2CtQ0ATlcW0nw2AwFLdPCAvSP8OiPSVCIkkxWyPKkaDr+gJs6GVLA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 > >