From nobody Tue Feb 10 02:54:58 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=fail(p=none dis=none) header.from=arm.com Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1658409730611466.916705190215; Thu, 21 Jul 2022 06:22:10 -0700 (PDT) Received: from list by lists.xenproject.org with outflank-mailman.372757.604723 (Exim 4.92) (envelope-from ) id 1oEW7h-0002vT-MZ; Thu, 21 Jul 2022 13:21:49 +0000 Received: by outflank-mailman (output) from mailman id 372757.604723; Thu, 21 Jul 2022 13:21:49 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1oEW7h-0002vK-Il; Thu, 21 Jul 2022 13:21:49 +0000 Received: by outflank-mailman (input) for mailman id 372757; Thu, 21 Jul 2022 13:21:48 +0000 Received: from se1-gles-flk1-in.inumbo.com ([94.247.172.50] helo=se1-gles-flk1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1oEW7f-0001je-Ro for xen-devel@lists.xenproject.org; Thu, 21 Jul 2022 13:21:47 +0000 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by se1-gles-flk1.inumbo.com (Halon) with ESMTP id 120ceba8-08f8-11ed-924f-1f966e50362f; Thu, 21 Jul 2022 15:21:46 +0200 (CEST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B30E723A; Thu, 21 Jul 2022 06:21:46 -0700 (PDT) Received: from a011292.shanghai.arm.com (a011292.shanghai.arm.com [10.169.190.94]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 93A0A3F73D; Thu, 21 Jul 2022 06:21:43 -0700 (PDT) X-Outflank-Mailman: Message body and most headers restored to incoming version 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" X-Inumbo-ID: 120ceba8-08f8-11ed-924f-1f966e50362f From: Penny Zheng To: xen-devel@lists.xenproject.org Cc: Penny Zheng , Stefano Stabellini , Julien Grall , Bertrand Marquis , Volodymyr Babchuk , Penny Zheng , Julien Grall Subject: [PATCH v6 4/9] xen/arm: introduce put_page_nr and get_page_nr Date: Thu, 21 Jul 2022 21:21:10 +0800 Message-Id: <20220721132115.3015761-5-Penny.Zheng@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220721132115.3015761-1-Penny.Zheng@arm.com> References: <20220721132115.3015761-1-Penny.Zheng@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZM-MESSAGEID: 1658409732766100002 Content-Type: text/plain; charset="utf-8" Later, we need to add the right amount of references, which should be the number of borrower domains, to the owner domain. Since we only have get_page() to increment the page reference by 1, a loop is needed per page, which is inefficient and time-consuming. To save the loop time, this commit introduces a set of new helpers put_page_nr() and get_page_nr() to increment/drop the page reference by nr. Signed-off-by: Penny Zheng Reviewed-by: Stefano Stabellini Reviewed-by: Julien Grall --- v6 change: - no change --- v5 change: - no change --- v4 changes: - fix the assert about checking overflow to make sure that the right equati= on return is at least equal to nr - simplify the assert about checking the underflow --- v3 changes: - check overflow with "n" - remove spurious change - bring back the check that we enter the loop only when count_info is greater than 0 --- v2 change: - new commit --- xen/arch/arm/include/asm/mm.h | 4 ++++ xen/arch/arm/mm.c | 42 +++++++++++++++++++++++++++-------- 2 files changed, 37 insertions(+), 9 deletions(-) diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h index c4bc3cd1e5..f1ab0fd030 100644 --- a/xen/arch/arm/include/asm/mm.h +++ b/xen/arch/arm/include/asm/mm.h @@ -343,6 +343,10 @@ void free_init_memory(void); int guest_physmap_mark_populate_on_demand(struct domain *d, unsigned long = gfn, unsigned int order); =20 +extern bool get_page_nr(struct page_info *page, const struct domain *domai= n, + unsigned long nr); +extern void put_page_nr(struct page_info *page, unsigned long nr); + extern void put_page_type(struct page_info *page); static inline void put_page_and_type(struct page_info *page) { diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c index 009b8cd9ef..d654980706 100644 --- a/xen/arch/arm/mm.c +++ b/xen/arch/arm/mm.c @@ -1587,21 +1587,29 @@ long arch_memory_op(int op, XEN_GUEST_HANDLE_PARAM(= void) arg) return 0; } =20 -struct domain *page_get_owner_and_reference(struct page_info *page) +static struct domain *page_get_owner_and_nr_reference(struct page_info *pa= ge, + unsigned long nr) { unsigned long x, y =3D page->count_info; struct domain *owner; =20 + /* Restrict nr to avoid "double" overflow */ + if ( nr >=3D PGC_count_mask ) + { + ASSERT_UNREACHABLE(); + return NULL; + } + do { x =3D y; /* * Count =3D=3D 0: Page is not allocated, so we cannot take a ref= erence. * Count =3D=3D -1: Reference count would wrap, which is invalid. */ - if ( unlikely(((x + 1) & PGC_count_mask) <=3D 1) ) + if ( unlikely(((x + nr) & PGC_count_mask) <=3D nr) ) return NULL; } - while ( (y =3D cmpxchg(&page->count_info, x, x + 1)) !=3D x ); + while ( (y =3D cmpxchg(&page->count_info, x, x + nr)) !=3D x ); =20 owner =3D page_get_owner(page); ASSERT(owner); @@ -1609,14 +1617,19 @@ struct domain *page_get_owner_and_reference(struct = page_info *page) return owner; } =20 -void put_page(struct page_info *page) +struct domain *page_get_owner_and_reference(struct page_info *page) +{ + return page_get_owner_and_nr_reference(page, 1); +} + +void put_page_nr(struct page_info *page, unsigned long nr) { unsigned long nx, x, y =3D page->count_info; =20 do { - ASSERT((y & PGC_count_mask) !=3D 0); + ASSERT((y & PGC_count_mask) >=3D nr); x =3D y; - nx =3D x - 1; + nx =3D x - nr; } while ( unlikely((y =3D cmpxchg(&page->count_info, x, nx)) !=3D x) ); =20 @@ -1626,19 +1639,30 @@ void put_page(struct page_info *page) } } =20 -bool get_page(struct page_info *page, const struct domain *domain) +void put_page(struct page_info *page) +{ + put_page_nr(page, 1); +} + +bool get_page_nr(struct page_info *page, const struct domain *domain, + unsigned long nr) { - const struct domain *owner =3D page_get_owner_and_reference(page); + const struct domain *owner =3D page_get_owner_and_nr_reference(page, n= r); =20 if ( likely(owner =3D=3D domain) ) return true; =20 if ( owner !=3D NULL ) - put_page(page); + put_page_nr(page, nr); =20 return false; } =20 +bool get_page(struct page_info *page, const struct domain *domain) +{ + return get_page_nr(page, domain, 1); +} + /* Common code requires get_page_type and put_page_type. * We don't care about typecounts so we just do the minimum to make it * happy. */ --=20 2.25.1