From patchwork Wed Jan 29 17:10:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Paul Durrant X-Patchwork-Id: 11356611 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7257E13A4 for ; Wed, 29 Jan 2020 17:12:01 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 447B4206D4 for ; Wed, 29 Jan 2020 17:12:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="nAc9lp/x" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 447B4206D4 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=amazon.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1iwqrg-0006KY-F8; Wed, 29 Jan 2020 17:10:56 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1iwqrf-0006KP-3i for xen-devel@lists.xenproject.org; Wed, 29 Jan 2020 17:10:55 +0000 X-Inumbo-ID: 4ecc7432-42ba-11ea-a933-bc764e2007e4 Received: from smtp-fw-9102.amazon.com (unknown [207.171.184.29]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 4ecc7432-42ba-11ea-a933-bc764e2007e4; Wed, 29 Jan 2020 17:10:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1580317855; x=1611853855; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=8c5ERSVSHTbXYDRSfW5NraYwBUPt1wDLT2y/xF2VfsI=; b=nAc9lp/xB6lms8OMOhEFoCAPlriEZCp9MOF+dNySG27upuOoe0fJDaRm vG0tbu7q6Gw05hI8mkA9RSi/NviNHd04MIp3nWfpZ6QdPU1kPRwd3bul7 ngR4a2qMzusf8hIbfCMcZ5KCKELKC4Est+KgiddGTBKKx4lSR7A5oOAtk 0=; IronPort-SDR: 4rN7P5YIcOcShi60KgezKryEltXx4dyjakZwQ3OSrqbE99hyF6tuJgbcItPw8YxJqgoWikimjp npxvEF6+lUBg== X-IronPort-AV: E=Sophos;i="5.70,378,1574121600"; d="scan'208";a="21841749" Received: from sea32-co-svc-lb4-vlan3.sea.corp.amazon.com (HELO email-inbound-relay-2c-6f38efd9.us-west-2.amazon.com) ([10.47.23.38]) by smtp-border-fw-out-9102.sea19.amazon.com with ESMTP; 29 Jan 2020 17:10:43 +0000 Received: from EX13MTAUEA002.ant.amazon.com (pdx4-ws-svc-p6-lb7-vlan3.pdx.amazon.com [10.170.41.166]) by email-inbound-relay-2c-6f38efd9.us-west-2.amazon.com (Postfix) with ESMTPS id 949C4A23FE; Wed, 29 Jan 2020 17:10:42 +0000 (UTC) Received: from EX13D32EUC002.ant.amazon.com (10.43.164.94) by EX13MTAUEA002.ant.amazon.com (10.43.61.77) with Microsoft SMTP Server (TLS) id 15.0.1236.3; Wed, 29 Jan 2020 17:10:42 +0000 Received: from EX13MTAUWB001.ant.amazon.com (10.43.161.207) by EX13D32EUC002.ant.amazon.com (10.43.164.94) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Wed, 29 Jan 2020 17:10:41 +0000 Received: from u2f063a87eabd5f.cbg10.amazon.com (10.125.106.135) by mail-relay.amazon.com (10.43.161.249) with Microsoft SMTP Server id 15.0.1367.3 via Frontend Transport; Wed, 29 Jan 2020 17:10:37 +0000 From: Paul Durrant To: Date: Wed, 29 Jan 2020 17:10:29 +0000 Message-ID: <20200129171030.1341-3-pdurrant@amazon.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200129171030.1341-1-pdurrant@amazon.com> References: <20200129171030.1341-1-pdurrant@amazon.com> MIME-Version: 1.0 Precedence: Bulk Subject: [Xen-devel] [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount safe to assign X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Stefano Stabellini , Julien Grall , Wei Liu , Konrad Rzeszutek Wilk , George Dunlap , Andrew Cooper , Paul Durrant , Ian Jackson , Volodymyr Babchuk , =?utf-8?q?Roger_Pau_Monn?= =?utf-8?q?=C3=A9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Currently it is unsafe to assign a domheap page allocated with MEMF_no_refcount to a domain because the domain't 'tot_pages' will not be incremented, but will be decrement when the page is freed (since free_domheap_pages() has no way of telling that the increment was skipped). This patch allocates a new 'count_info' bit for a PGC_extra flag which is then used to mark pages when alloc_domheap_pages() is called with MEMF_no_refcount. The MEMF_no_refcount is *not* passed through to assign_pages() because it still needs to call domain_adjust_tot_pages() to make sure the domain is appropriately referenced. assign_pages() is accordingly modified to account pages marked with PGC_extra to an 'extra_pages' counter, which is then subtracted from 'tot_pages' before it is checked against 'max_pages', thus avoiding over-allocation errors. NOTE: steal_page() is also modified to decrement extra_pages in the case of a PGC_extra page being stolen from a domain. Also, whilst adding the extra_pages counter into struct domain, make some cosmetic fixes to comments for neighbouring fields. Signed-off-by: Paul Durrant --- Cc: Andrew Cooper Cc: George Dunlap Cc: Ian Jackson Cc: Jan Beulich Cc: Julien Grall Cc: Konrad Rzeszutek Wilk Cc: Stefano Stabellini Cc: Wei Liu Cc: Volodymyr Babchuk Cc: "Roger Pau Monné" v7: - s/PGC_no_refcount/PGC_extra/g - Re-work allocation to account for 'extra' pages, also making it safe to assign PGC_extra pages post-allocation v6: - Add an extra ASSERT into assign_pages() that PGC_no_refcount is not set if MEMF_no_refcount is clear - ASSERT that count_info is 0 in alloc_domheap_pages() and set to PGC_no_refcount rather than ORing v5: - Make sure PGC_no_refcount is set before assign_pages() is called - Don't bother to clear PGC_no_refcount in free_domheap_pages() and drop ASSERT in free_heap_pages() - Don't latch count_info in free_heap_pages() v4: - New in v4 --- xen/arch/x86/mm.c | 5 ++++ xen/common/page_alloc.c | 49 +++++++++++++++++++++++++++++----------- xen/include/asm-arm/mm.h | 5 +++- xen/include/asm-x86/mm.h | 7 ++++-- xen/include/xen/sched.h | 18 ++++++++------- 5 files changed, 60 insertions(+), 24 deletions(-) diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c index f50c065af3..5b04db8c21 100644 --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -4266,6 +4266,11 @@ int steal_page( page_list_del(page, &d->page_list); /* Unlink from original owner. */ + if ( page->count_info & PGC_extra ) + { + ASSERT(d->extra_pages); + d->extra_pages--; + } if ( !(memflags & MEMF_no_refcount) && !domain_adjust_tot_pages(d, -1) ) drop_dom_ref = true; diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c index 919a270587..a2d69f222a 100644 --- a/xen/common/page_alloc.c +++ b/xen/common/page_alloc.c @@ -2256,6 +2256,7 @@ int assign_pages( { int rc = 0; unsigned long i; + unsigned int extra_pages = 0; spin_lock(&d->page_alloc_lock); @@ -2267,13 +2268,19 @@ int assign_pages( goto out; } + for ( i = 0; i < (1 << order); i++ ) + if ( pg[i].count_info & PGC_extra ) + extra_pages++; + if ( !(memflags & MEMF_no_refcount) ) { - if ( unlikely((d->tot_pages + (1 << order)) > d->max_pages) ) + unsigned int max_pages = d->max_pages - d->extra_pages - extra_pages; + + if ( unlikely((d->tot_pages + (1 << order)) > max_pages) ) { gprintk(XENLOG_INFO, "Over-allocation for domain %u: " "%u > %u\n", d->domain_id, - d->tot_pages + (1 << order), d->max_pages); + d->tot_pages + (1 << order), max_pages); rc = -E2BIG; goto out; } @@ -2282,13 +2289,17 @@ int assign_pages( get_knownalive_domain(d); } + d->extra_pages += extra_pages; for ( i = 0; i < (1 << order); i++ ) { + unsigned long count_info = pg[i].count_info; + ASSERT(page_get_owner(&pg[i]) == NULL); - ASSERT(!pg[i].count_info); + ASSERT(!(count_info & ~PGC_extra)); page_set_owner(&pg[i], d); smp_wmb(); /* Domain pointer must be visible before updating refcnt. */ - pg[i].count_info = PGC_allocated | 1; + count_info &= PGC_extra; + pg[i].count_info = count_info | PGC_allocated | 1; page_list_add_tail(&pg[i], &d->page_list); } @@ -2314,11 +2325,6 @@ struct page_info *alloc_domheap_pages( if ( memflags & MEMF_no_owner ) memflags |= MEMF_no_refcount; - else if ( (memflags & MEMF_no_refcount) && d ) - { - ASSERT(!(memflags & MEMF_no_refcount)); - return NULL; - } if ( !dma_bitsize ) memflags &= ~MEMF_no_dma; @@ -2331,11 +2337,23 @@ struct page_info *alloc_domheap_pages( memflags, d)) == NULL)) ) return NULL; - if ( d && !(memflags & MEMF_no_owner) && - assign_pages(d, pg, order, memflags) ) + if ( d && !(memflags & MEMF_no_owner) ) { - free_heap_pages(pg, order, memflags & MEMF_no_scrub); - return NULL; + if ( memflags & MEMF_no_refcount ) + { + unsigned long i; + + for ( i = 0; i < (1ul << order); i++ ) + { + ASSERT(!pg[i].count_info); + pg[i].count_info = PGC_extra; + } + } + if ( assign_pages(d, pg, order, memflags & ~MEMF_no_refcount) ) + { + free_heap_pages(pg, order, memflags & MEMF_no_scrub); + return NULL; + } } return pg; @@ -2383,6 +2401,11 @@ void free_domheap_pages(struct page_info *pg, unsigned int order) BUG(); } arch_free_heap_page(d, &pg[i]); + if ( pg[i].count_info & PGC_extra ) + { + ASSERT(d->extra_pages); + d->extra_pages--; + } } drop_dom_ref = !domain_adjust_tot_pages(d, -(1 << order)); diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h index 333efd3a60..7df91280bc 100644 --- a/xen/include/asm-arm/mm.h +++ b/xen/include/asm-arm/mm.h @@ -119,9 +119,12 @@ struct page_info #define PGC_state_offlined PG_mask(2, 9) #define PGC_state_free PG_mask(3, 9) #define page_state_is(pg, st) (((pg)->count_info&PGC_state) == PGC_state_##st) +/* Page is not reference counted */ +#define _PGC_extra PG_shift(10) +#define PGC_extra PG_mask(1, 10) /* Count of references to this frame. */ -#define PGC_count_width PG_shift(9) +#define PGC_count_width PG_shift(10) #define PGC_count_mask ((1UL<count_info&PGC_state) == PGC_state_##st) +/* Page is not reference counted */ +#define _PGC_extra PG_shift(10) +#define PGC_extra PG_mask(1, 10) - /* Count of references to this frame. */ -#define PGC_count_width PG_shift(9) +/* Count of references to this frame. */ +#define PGC_count_width PG_shift(10) #define PGC_count_mask ((1UL<