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 C10ADC433EF for ; Fri, 24 Jun 2022 19:18:40 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.355846.583772 (Exim 4.92) (envelope-from ) id 1o4op3-0004YZ-0Y; Fri, 24 Jun 2022 19:18:29 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 355846.583772; Fri, 24 Jun 2022 19:18:28 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1o4op2-0004YS-U3; Fri, 24 Jun 2022 19:18:28 +0000 Received: by outflank-mailman (input) for mailman id 355846; Fri, 24 Jun 2022 19:18:28 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1o4op2-0004Y7-8B for xen-devel@lists.xenproject.org; Fri, 24 Jun 2022 19:18:28 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1o4op1-0005yQ-Va; Fri, 24 Jun 2022 19:18:27 +0000 Received: from 54-240-197-238.amazon.com ([54.240.197.238] helo=[192.168.4.76]) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1o4op1-0000B4-Oh; Fri, 24 Jun 2022 19:18:27 +0000 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" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID; bh=I4Fwegyrc1IZQItWF5i8KJDAzGvkaQ79eiPkaAvvogs=; b=v+/p9wzC/UoVO94s9LOzsFujuC +adZaDA4TZ/N+dgQSD74dwvcqAyVKTCHSugEVpf7JHHBUiORzh/w1lDTu3GhsDuRBE1QK3Ct60s6o NM2Aal0FKPadFlIJq6CvFZwfBavONAkRd6G85e7Jqxk9yXshbBRZx2C4ygBtJS0Si0xk=; Message-ID: <3e397ff3-0b67-523c-179a-0a2035b081da@xen.org> Date: Fri, 24 Jun 2022 20:18:25 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH v5 5/8] xen/arm: Add additional reference to owner domain when the owner is allocated To: Penny Zheng , xen-devel@lists.xenproject.org Cc: wei.chen@arm.com, Stefano Stabellini , Bertrand Marquis , Volodymyr Babchuk References: <20220620051114.210118-1-Penny.Zheng@arm.com> <20220620051114.210118-6-Penny.Zheng@arm.com> From: Julien Grall In-Reply-To: <20220620051114.210118-6-Penny.Zheng@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Penny, On 20/06/2022 06:11, Penny Zheng wrote: > Borrower domain will fail to get a page ref using the owner domain > during allocation, when the owner is created after borrower. > > So here, we decide to get and add the right amount of reference, which > is the number of borrowers, when the owner is allocated. > > Signed-off-by: Penny Zheng > Reviewed-by: Stefano Stabellini > --- > v5 change: > - no change > --- > v4 changes: > - no change > --- > v3 change: > - printk rather than dprintk since it is a serious error > --- > v2 change: > - new commit > --- > xen/arch/arm/domain_build.c | 62 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 62 insertions(+) > > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c > index d4fd64e2bd..650d18f5ef 100644 > --- a/xen/arch/arm/domain_build.c > +++ b/xen/arch/arm/domain_build.c > @@ -799,6 +799,34 @@ static mfn_t __init acquire_shared_memory_bank(struct domain *d, > > } > > +static int __init acquire_nr_borrower_domain(struct domain *d, > + paddr_t pbase, paddr_t psize, > + unsigned long *nr_borrowers) > +{ > + unsigned long bank; > + > + /* Iterate reserved memory to find requested shm bank. */ > + for ( bank = 0 ; bank < bootinfo.reserved_mem.nr_banks; bank++ ) > + { > + paddr_t bank_start = bootinfo.reserved_mem.bank[bank].start; > + paddr_t bank_size = bootinfo.reserved_mem.bank[bank].size; > + > + if ( pbase == bank_start && psize == bank_size ) > + break; > + } > + > + if ( bank == bootinfo.reserved_mem.nr_banks ) > + return -ENOENT; > + > + if ( d == dom_io ) > + *nr_borrowers = bootinfo.reserved_mem.bank[bank].nr_shm_domain; > + else > + /* Exclude the owner domain itself. */ NIT: I think this comment wants to be just above the 'if' and expanded to explain why the "dom_io" is not included. AFAIU, this is because "dom_io" is not described in the Device-Tree, so it would not be taken into account for nr_shm_domain. > + *nr_borrowers = bootinfo.reserved_mem.bank[bank].nr_shm_domain - 1; TBH, given the use here. I would have consider to not increment nr_shm_domain if the role was owner in parsing code. This is v5 now, so I would be OK with the comment above. But I would suggest to consider it as a follow-up. > + > + return 0; > +} > + > /* > * Func allocate_shared_memory is supposed to be only called > * from the owner. > @@ -810,6 +838,8 @@ static int __init allocate_shared_memory(struct domain *d, > { > mfn_t smfn; > int ret = 0; > + unsigned long nr_pages, nr_borrowers, i; > + struct page_info *page; > > dprintk(XENLOG_INFO, > "Allocate static shared memory BANK %#"PRIpaddr"-%#"PRIpaddr".\n", > @@ -824,6 +854,7 @@ static int __init allocate_shared_memory(struct domain *d, > * DOMID_IO is the domain, like DOMID_XEN, that is not auto-translated. > * It sees RAM 1:1 and we do not need to create P2M mapping for it > */ > + nr_pages = PFN_DOWN(psize); > if ( d != dom_io ) > { > ret = guest_physmap_add_pages(d, gaddr_to_gfn(gbase), smfn, PFN_DOWN(psize)); > @@ -835,6 +866,37 @@ static int __init allocate_shared_memory(struct domain *d, > } > } > > + /* > + * Get the right amount of references per page, which is the number of > + * borrow domains. > + */ > + ret = acquire_nr_borrower_domain(d, pbase, psize, &nr_borrowers); > + if ( ret ) > + return ret; > + > + /* > + * Instead of let borrower domain get a page ref, we add as many Typo: s/let/letting/ > + * additional reference as the number of borrowers when the owner > + * is allocated, since there is a chance that owner is created > + * after borrower. What if the borrower is created first? Wouldn't this result to add pages in the P2M without reference? If yes, then I think this is worth an explaination. > + */ > + page = mfn_to_page(smfn); Where do you validate the range [smfn, nr_pages]? > + for ( i = 0; i < nr_pages; i++ ) > + { > + if ( !get_page_nr(page + i, d, nr_borrowers) ) > + { > + printk(XENLOG_ERR > + "Failed to add %lu references to page %"PRI_mfn".\n", > + nr_borrowers, mfn_x(smfn) + i); > + goto fail; > + } > + } > + > + return 0; > + > + fail: > + while ( --i >= 0 ) > + put_page_nr(page + i, nr_borrowers); > return ret; > } > Cheers, -- Julien Grall