From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752513AbcAGCUl (ORCPT ); Wed, 6 Jan 2016 21:20:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53045 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751924AbcAGCUk (ORCPT ); Wed, 6 Jan 2016 21:20:40 -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> 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: <568DCB6F.4030208@redhat.com> Date: Thu, 7 Jan 2016 10:20:31 +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: <568DC9F0.8090609@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 10:14 AM, Xunlei Pang wrote: > On 01/07/2016 at 01:08 AM, Minfei Huang wrote: >> On 01/06/16 at 05:50pm, Xunlei Pang wrote: >>> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c >>> index 819ab3f..cda867d 100644 >>> --- a/arch/x86/kernel/machine_kexec_64.c >>> +++ b/arch/x86/kernel/machine_kexec_64.c >>> @@ -536,3 +536,44 @@ overflow: >>> return -ENOEXEC; >>> } >>> #endif /* CONFIG_KEXEC_FILE */ >>> + >>> +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. > >> 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 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; > + > + page = pfn_to_page(start >> PAGE_SHIFT); > + nr_pages = (end >> PAGE_SHIFT) - (start >> PAGE_SHIFT) + 1; > + 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); > + > + /* 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; In fact, control code page is only 1 page, using control + 2*PAGE_SIZE is clearer. For example, if we have more other type pages following it. Anyway this is not that important. Regards, Xunlei > + kexec_mark_range(control, crashk_res.end, protect); > +} > + > +void arch_kexec_protect_crashkres(void) > +{ > + kexec_mark_crashkres(true); > +} > + > +void arch_kexec_unprotect_crashkres(void) > +{ > + kexec_mark_crashkres(false); > +} > >> Thanks >> Minfei >> >> _______________________________________________ >> kexec mailing list >> kexec@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/kexec > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/