From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1aH2oc-0005jn-NZ for kexec@lists.infradead.org; Thu, 07 Jan 2016 05:08:51 +0000 Subject: Re: [PATCH v2 2/2] kexec: Provide arch_kexec_protect(unprotect)_crashkres() References: <1452073845-1474-1-git-send-email-xlpang@redhat.com> <1452073845-1474-2-git-send-email-xlpang@redhat.com> <20160106170832.GB25832@dhcp-128-25.nay.redhat.com> <568DC9F0.8090609@redhat.com> <20160107023637.GA12526@dhcp-128-25.nay.redhat.com> From: Xunlei Pang Message-ID: <568DF2C5.9080701@redhat.com> Date: Thu, 7 Jan 2016 13:08:21 +0800 MIME-Version: 1.0 In-Reply-To: <20160107023637.GA12526@dhcp-128-25.nay.redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Minfei Huang Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org, ebiederm@xmission.com, akpm@linux-foundation.org, Dave Young , Vivek Goyal On 01/07/2016 at 10:36 AM, Minfei Huang wrote: > On 01/07/16 at 10:14am, Xunlei Pang wrote: >>>> +static int >>>> +kexec_mark_range(unsigned long start, unsigned long end, bool protect) >>>> +{ >>>> + struct page *page; >>>> + unsigned int nr_pages; >>>> + >>>> + /* For physical range: [start, end] */ >>>> + if (!start || !end || start > end) >>>> + return 0; >>> Hi, Xunlei. >>> >>> if (start > end) >>> return 0; >> If both start and end are zero, we want to return directly, so the two >> more check doesn't hurt. > How about if the start is equal to 0, and end is larger than 0? It is > better to make code more robust, although it never happen in currect > kexec code. Hmm, this will be better: if (!end || start > end) return 0; it handles the common case not using crash_low_res(start and end are 0). Regards, Xunlei > >>> See the below comment. >>>> + >>>> + page = pfn_to_page(start >> PAGE_SHIFT); >>>> + nr_pages = (end + PAGE_SIZE - start) >> PAGE_SHIFT; >>> As I commented in last version, it is better to cover the case if the >>> range from start to end acrosses two pages. >> right. >> >>>> + if (protect) >>>> + return set_pages_ro(page, nr_pages); >>>> + else >>>> + return set_pages_rw(page, nr_pages); >>>> +} >>>> + >>>> +static void kexec_mark_crashkres(bool protect) >>>> +{ >>>> + unsigned long control; >>>> + >>>> + kexec_mark_range(crashk_low_res.start, crashk_low_res.end, protect); >>> Adding the following if test to test crashk_low_res is better. Then we >>> do not need to test if start or end is equal to 0 in kexec_mark_range. >>> >>> if (crashk_low_res.start != crashk_low_res.end) { >>> kexec_mark_range(crashk_low_res.start, >>> crashk_low_res.end, protect); >>> } >> The checks in kexec_mark_range() will handle the case, it's not >> performance-critical path and will make the code less clean. >> >>>> + >>>> + /* Don't touch the control code page used in crash_kexec().*/ >>>> + control = PFN_PHYS(page_to_pfn(kexec_crash_image->control_code_page)); >>>> + /* Control code page is located in the 2nd page. */ >>>> + kexec_mark_range(crashk_res.start, control + PAGE_SIZE - 1, protect); >>>> + kexec_mark_range(control + 2 * PAGE_SIZE, crashk_res.end, protect); >>> I think it is more readable, if we use MACRO KEXEC_CONTROL_PAGE_SIZE, >>> instead of using 2*PAGE_SIZE directly. >> OK. >> >> How about the following update: >> +static void kexec_mark_crashkres(bool protect) >> +{ >> + unsigned long control; >> + >> + kexec_mark_range(crashk_low_res.start, crashk_low_res.end, protect); >> + >> + /* Don't touch the control code page used in crash_kexec().*/ >> + control = PFN_PHYS(page_to_pfn(kexec_crash_image->control_code_page)); >> + /* Control code page is located in the 2nd page. */ >> + kexec_mark_range(crashk_res.start, control + PAGE_SIZE - 1, protect); >> + control += KEXEC_CONTROL_PAGE_SIZE; >> + kexec_mark_range(control, crashk_res.end, protect); >> +} > I'm fine with this. > > Thanks > Minfei > > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750890AbcAGFIc (ORCPT ); Thu, 7 Jan 2016 00:08:32 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43299 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750707AbcAGFI2 (ORCPT ); Thu, 7 Jan 2016 00:08:28 -0500 Subject: Re: [PATCH v2 2/2] kexec: Provide arch_kexec_protect(unprotect)_crashkres() To: Minfei Huang References: <1452073845-1474-1-git-send-email-xlpang@redhat.com> <1452073845-1474-2-git-send-email-xlpang@redhat.com> <20160106170832.GB25832@dhcp-128-25.nay.redhat.com> <568DC9F0.8090609@redhat.com> <20160107023637.GA12526@dhcp-128-25.nay.redhat.com> Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org, ebiederm@xmission.com, akpm@linux-foundation.org, Dave Young , Vivek Goyal From: Xunlei Pang Message-ID: <568DF2C5.9080701@redhat.com> Date: Thu, 7 Jan 2016 13:08:21 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <20160107023637.GA12526@dhcp-128-25.nay.redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/07/2016 at 10:36 AM, Minfei Huang wrote: > On 01/07/16 at 10:14am, Xunlei Pang wrote: >>>> +static int >>>> +kexec_mark_range(unsigned long start, unsigned long end, bool protect) >>>> +{ >>>> + struct page *page; >>>> + unsigned int nr_pages; >>>> + >>>> + /* For physical range: [start, end] */ >>>> + if (!start || !end || start > end) >>>> + return 0; >>> Hi, Xunlei. >>> >>> if (start > end) >>> return 0; >> If both start and end are zero, we want to return directly, so the two >> more check doesn't hurt. > How about if the start is equal to 0, and end is larger than 0? It is > better to make code more robust, although it never happen in currect > kexec code. Hmm, this will be better: if (!end || start > end) return 0; it handles the common case not using crash_low_res(start and end are 0). Regards, Xunlei > >>> See the below comment. >>>> + >>>> + page = pfn_to_page(start >> PAGE_SHIFT); >>>> + nr_pages = (end + PAGE_SIZE - start) >> PAGE_SHIFT; >>> As I commented in last version, it is better to cover the case if the >>> range from start to end acrosses two pages. >> right. >> >>>> + if (protect) >>>> + return set_pages_ro(page, nr_pages); >>>> + else >>>> + return set_pages_rw(page, nr_pages); >>>> +} >>>> + >>>> +static void kexec_mark_crashkres(bool protect) >>>> +{ >>>> + unsigned long control; >>>> + >>>> + kexec_mark_range(crashk_low_res.start, crashk_low_res.end, protect); >>> Adding the following if test to test crashk_low_res is better. Then we >>> do not need to test if start or end is equal to 0 in kexec_mark_range. >>> >>> if (crashk_low_res.start != crashk_low_res.end) { >>> kexec_mark_range(crashk_low_res.start, >>> crashk_low_res.end, protect); >>> } >> The checks in kexec_mark_range() will handle the case, it's not >> performance-critical path and will make the code less clean. >> >>>> + >>>> + /* Don't touch the control code page used in crash_kexec().*/ >>>> + control = PFN_PHYS(page_to_pfn(kexec_crash_image->control_code_page)); >>>> + /* Control code page is located in the 2nd page. */ >>>> + kexec_mark_range(crashk_res.start, control + PAGE_SIZE - 1, protect); >>>> + kexec_mark_range(control + 2 * PAGE_SIZE, crashk_res.end, protect); >>> I think it is more readable, if we use MACRO KEXEC_CONTROL_PAGE_SIZE, >>> instead of using 2*PAGE_SIZE directly. >> OK. >> >> How about the following update: >> +static void kexec_mark_crashkres(bool protect) >> +{ >> + unsigned long control; >> + >> + kexec_mark_range(crashk_low_res.start, crashk_low_res.end, protect); >> + >> + /* Don't touch the control code page used in crash_kexec().*/ >> + control = PFN_PHYS(page_to_pfn(kexec_crash_image->control_code_page)); >> + /* Control code page is located in the 2nd page. */ >> + kexec_mark_range(crashk_res.start, control + PAGE_SIZE - 1, protect); >> + control += KEXEC_CONTROL_PAGE_SIZE; >> + kexec_mark_range(control, crashk_res.end, protect); >> +} > I'm fine with this. > > Thanks > Minfei > > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec