Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751464AbbL1Gcl (ORCPT ); Mon, 28 Dec 2015 01:32:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33121 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750929AbbL1Gci (ORCPT ); Mon, 28 Dec 2015 01:32:38 -0500 Subject: Re: [PATCH 2/2] kexec: Provide arch_kexec_protect(unprotect)_crashkres() To: Dave Young References: <1450869146-6186-1-git-send-email-xlpang@redhat.com> <1450869146-6186-2-git-send-email-xlpang@redhat.com> <20151224055425.GC3480@dhcp-128-65.nay.redhat.com> <567B8B44.9070807@redhat.com> <20151224061616.GD3480@dhcp-128-65.nay.redhat.com> <567B9444.1050608@redhat.com> Cc: akpm@linux-foundation.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, vgoyal@redhat.com, Eric Biederman From: Xunlei Pang Message-ID: <5680D780.4070709@redhat.com> Date: Mon, 28 Dec 2015 14:32:32 +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: <567B9444.1050608@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 Content-Length: 4569 Lines: 132 On 12/24/2015 at 02:44 PM, Xunlei Pang wrote: > On 12/24/2015 at 02:16 PM, Dave Young wrote: >> Hi, Xunlei >> >> On 12/24/15 at 02:05pm, Xunlei Pang wrote: >>> On 12/24/2015 at 01:54 PM, Dave Young wrote: >>>> Ccing Vivek >>>> >>>> On 12/23/15 at 07:12pm, Xunlei Pang wrote: >>>>> Implement the protection method for the crash kernel memory >>>>> reservation for the 64-bit x86 kdump. >>>>> >>>>> Signed-off-by: Xunlei Pang >>>>> --- >>>>> Only provided x86_64 implementation, as I've only tested on x86_64 so far. >>>>> >>>>> arch/x86/kernel/machine_kexec_64.c | 43 ++++++++++++++++++++++++++++++++++++++ >>>>> 1 file changed, 43 insertions(+) >>>>> >>>>> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c >>>>> index 819ab3f..a3d289c 100644 >>>>> --- a/arch/x86/kernel/machine_kexec_64.c >>>>> +++ b/arch/x86/kernel/machine_kexec_64.c >>>>> @@ -536,3 +536,46 @@ overflow: >>>>> return -ENOEXEC; >>>>> } >>>>> #endif /* CONFIG_KEXEC_FILE */ >>>>> + >>>>> +#ifdef CONFIG_KEXEC_CORE >>>> The file is only compiled when CONFIG_KEXEC_CORE=y so #ifdef is not necessary >>> Yes, indeed. I'll remove this macro and send v2 later. >>> >>>>> +static int >>>>> +kexec_mark_range(unsigned long start, unsigned long end, bool protect) >>>>> +{ >>>>> + struct page *page; >>>>> + unsigned int nr_pages; >>>>> + >>>>> + if (!start || !end || start >= end) >>>>> + return 0; >>>>> + >>>>> + page = pfn_to_page(start >> PAGE_SHIFT); >>>>> + nr_pages = (end + 1 - start) >> PAGE_SHIFT; >>>>> + if (protect) >>>>> + return set_pages_ro(page, nr_pages); >>>>> + else >>>>> + return set_pages_rw(page, nr_pages); >>>> May use set_memory_ro/rw to avoid converting to *page? >>> on x86 it just a wrapper of set_memory_ro/rw, I think both are ok. >> Ok, I have no strong opinion on that.. >> >>>>> +} >>>>> + >>>>> +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. */ >>>>> + control = control + PAGE_SIZE; >> Though it works because the control code is less than 1 page, but use the macro >> of KEXEC_CONTROL_PAGE_SIZE looks better.. The 1st page is pagetable, control code page locates at the 2nd page. The following kexec_mark_range() wants to mark ro from crashk_res.start to the 1st page(included), so here we must use PAGE_SIZE. >> >>>>> + kexec_mark_range(crashk_res.start, control - 1, protect); >>>>> + kexec_mark_range(control + PAGE_SIZE, crashk_res.end, protect); >>>> X86 kexec will copy the page while kexecing, could you check if we can move >>>> that copying to earliyer while kexec loading, maybe machine_kexec_prepare so >>>> that we can make a arch-independent implementation. >>> For some arch, may use huge tlb directly to do the kernel mapping, >>> in such cases, we can't implement this function. So I think it should >>> be arch-dependent. >> Ok, that's fine. > At least moving the x86 control-copying code into arch-related > machine_kexec_prepare() should work, and this can omit the > special treatment of the control code page. The "relocate_kernel" routine in "relocate_kernel_64.S" will use it as a temp storage "for jumping back"(as its comment), so we can't mark it readonly. > > Regards, > Xunlei > >>> Regards, >>> Xunlei >>> >>>>> +} >>>>> + >>>>> +void arch_kexec_protect_crashkres(void) >>>>> +{ >>>>> + kexec_mark_crashkres(true); >>>>> +} >>>>> + >>>>> +void arch_kexec_unprotect_crashkres(void) >>>>> +{ >>>>> + kexec_mark_crashkres(false); >>>>> +} >>>>> +#endif >>>>> -- >>>>> 2.5.0 >>>>> >>>>> >>>>> _______________________________________________ >>>>> 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 >> Thanks >> Dave >> >> _______________________________________________ >> 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/