Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755781AbcCaDwO (ORCPT ); Wed, 30 Mar 2016 23:52:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51859 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751595AbcCaDwM (ORCPT ); Wed, 30 Mar 2016 23:52:12 -0400 Reply-To: xlpang@redhat.com Subject: Re: [PATCH] s390/kexec: Consolidate crash_map/unmap_reserved_pages() and arch_kexec_protect(unprotect)_crashkres() References: <1459338441-21919-1-git-send-email-xlpang@redhat.com> <20160330123026.GB2607@x1.redhat.com> <20160331024309.GA16292@dhcp-128-25.nay.redhat.com> <20160331025255.GB2555@x1.redhat.com> To: Baoquan He , Minfei Huang Cc: Xunlei Pang , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, ebiederm@xmission.com, akpm@linux-foundation.org, Michael Holzheu , Vivek Goyal From: Xunlei Pang Message-ID: <56FC9EE7.7020506@redhat.com> Date: Thu, 31 Mar 2016 11:52:07 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20160331025255.GB2555@x1.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: 13172 Lines: 366 Hi Bao, On 2016/03/31 at 10:52, Baoquan He wrote: > On 03/31/16 at 10:43am, Minfei Huang wrote: >> On 03/30/16 at 08:30pm, Baoquan He wrote: >>> Hi Xunlei, >>> >>> I have two questions. >>> >>> One is do we still need Minfei's patch if this patch is applied since >>> you have completely delete crash_map/unmap_reserved_pages in >>> kernel/kexec.c ? >> I think it is necessary to apply my bug-fixing patch firstly before >> apply this, since other maintainers can backport my bug-fixing patch to >> fix issue for stable linux kernel. > This is why previously I said you two need get together to discuss how > to fix this issue and post. Two questions: 1st is Xunlei is doing a > cleanup but leave the map/unmap there thought they are doing the same > thing in different way; 2nd is your bug fix patch with his clean up. It > looks totally mess, to reviewers and maintainers. So now I will leave > these to other people interested to review because I personally don't > like it, but I don't object it strongly since I don't like always aruging > by type writing. > Thanks for your comments, and I'm fine with your concern. There is a "historical" reason, we didn't expect these patches back then, they were coming out gradually due to some discussion in the mailinglist. It would be clear if these patches were reordered as follows: Minfei's patchset: [Patch01] kexec: make a pair of map/unmap reserved pages in error path [Patch02] kexec: do a cleanup for function kexec_load Then my patchset: [Patch01] kexec: introduce a protection mechanism for the crashkernel reserved memory [Patch02] s390/kexec: Consolidate crash_map/unmap_reserved_pages() and arch_kexec_protect(unprotect)_crashkres() [Patch03(x86_64)] kexec: provide arch_kexec_protect(unprotect)_crashkres() I don't know if it is possible to reorder that since they are already in "linux-next", ask Andrew for help :-) Regards, Xunlei >> Thanks >> Minfei >> >>> On 03/30/16 at 07:47pm, Xunlei Pang wrote: >>>> Commit 3f625002581b ("kexec: introduce a protection mechanism >>>> for the crashkernel reserved memory") is a similar mechanism >>>> for protecting the crash kernel reserved memory to previous >>>> crash_map/unmap_reserved_pages() implementation, the new one >>>> is more generic in name and cleaner in code (besides, some >>>> arch may not be allowed to unmap the pgtable). >>>> >>>> Therefore, this patch consolidates them, and uses the new >>>> arch_kexec_protect(unprotect)_crashkres() to replace former >>>> crash_map/unmap_reserved_pages() which by now has been only >>>> used by S390. >>>> >>>> The consolidation work needs the crash memory to be mapped >>>> initially, so get rid of S390 crash kernel memblock removal >>>> in reserve_crashkernel(). Once kdump kernel is loaded, the >>>> new arch_kexec_protect_crashkres() implemented for S390 will >>>> actually unmap the pgtable like before. >>>> >>>> The patch also fixed a S390 crash_shrink_memory() bad page warning >>>> in passing due to not using memblock_reserve(): >>>> BUG: Bad page state in process bash pfn:7e400 >>>> page:000003d101f90000 count:0 mapcount:1 mapping: (null) index:0x0 >>>> flags: 0x0() >>>> page dumped because: nonzero mapcount >>>> Modules linked in: ghash_s390 prng aes_s390 des_s390 des_generic >>>> CPU: 0 PID: 1558 Comm: bash Not tainted 4.6.0-rc1-next-20160327 #1 >>>> 0000000073007a58 0000000073007ae8 0000000000000002 0000000000000000 >>>> 0000000073007b88 0000000073007b00 0000000073007b00 000000000022cf4e >>>> 0000000000a579b8 00000000007b0dd6 0000000000791a8c >>>> 000000000000000b >>>> 0000000073007b48 0000000073007ae8 0000000000000000 0000000000000000 >>>> 070003d100000001 0000000000112f20 0000000073007ae8 0000000073007b48 >>>> Call Trace: >>>> ([<0000000000112e0c>] show_trace+0x5c/0x78) >>>> ([<0000000000112ed4>] show_stack+0x6c/0xe8) >>>> ([<00000000003f28dc>] dump_stack+0x84/0xb8) >>>> ([<0000000000235454>] bad_page+0xec/0x158) >>>> ([<00000000002357a4>] free_pages_prepare+0x2e4/0x308) >>>> ([<00000000002383a2>] free_hot_cold_page+0x42/0x198) >>>> ([<00000000001c45e0>] crash_free_reserved_phys_range+0x60/0x88) >>>> ([<00000000001c49b0>] crash_shrink_memory+0xb8/0x1a0) >>>> ([<000000000015bcae>] kexec_crash_size_store+0x46/0x60) >>>> ([<000000000033d326>] kernfs_fop_write+0x136/0x180) >>>> ([<00000000002b253c>] __vfs_write+0x3c/0x100) >>>> ([<00000000002b35ce>] vfs_write+0x8e/0x190) >>>> ([<00000000002b4ca0>] SyS_write+0x60/0xd0) >>>> ([<000000000063067c>] system_call+0x244/0x264) >>>> >>>> Cc: Michael Holzheu >>>> Signed-off-by: Xunlei Pang >>>> --- >>>> Tested kexec/kdump on S390x >>>> >>>> arch/s390/kernel/machine_kexec.c | 86 ++++++++++++++++++++++------------------ >>>> arch/s390/kernel/setup.c | 7 ++-- >>>> include/linux/kexec.h | 2 - >>>> kernel/kexec.c | 12 ------ >>>> kernel/kexec_core.c | 11 +---- >>>> 5 files changed, 54 insertions(+), 64 deletions(-) >>>> >>>> diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c >>>> index 2f1b721..1ec6cfc 100644 >>>> --- a/arch/s390/kernel/machine_kexec.c >>>> +++ b/arch/s390/kernel/machine_kexec.c >>>> @@ -35,6 +35,52 @@ extern const unsigned long long relocate_kernel_len; >>>> #ifdef CONFIG_CRASH_DUMP >>>> >>>> /* >>>> + * Map or unmap crashkernel memory >>>> + */ >>>> +static void crash_map_pages(int enable) >>>> +{ >>>> + unsigned long size = resource_size(&crashk_res); >>>> + >>>> + BUG_ON(crashk_res.start % KEXEC_CRASH_MEM_ALIGN || >>>> + size % KEXEC_CRASH_MEM_ALIGN); >>>> + if (enable) >>>> + vmem_add_mapping(crashk_res.start, size); >>>> + else { >>>> + vmem_remove_mapping(crashk_res.start, size); >>>> + if (size) >>>> + os_info_crashkernel_add(crashk_res.start, size); >>>> + else >>>> + os_info_crashkernel_add(0, 0); >>>> + } >>>> +} >>>> + >>>> +/* >>>> + * Map crashkernel memory >>>> + */ >>>> +static void crash_map_reserved_pages(void) >>>> +{ >>>> + crash_map_pages(1); >>>> +} >>>> + >>>> +/* >>>> + * Unmap crashkernel memory >>>> + */ >>>> +static void crash_unmap_reserved_pages(void) >>>> +{ >>>> + crash_map_pages(0); >>>> +} >>>> + >>>> +void arch_kexec_protect_crashkres(void) >>> The second is in kernel I saw res is abbreviation of resource. So here >>> what is the full name of crashkres? >>> >>> >>>> +{ >>>> + crash_unmap_reserved_pages(); >>>> +} >>>> + >>>> +void arch_kexec_unprotect_crashkres(void) >>>> +{ >>>> + crash_map_reserved_pages(); >>>> +} >>>> + >>>> +/* >>>> * PM notifier callback for kdump >>>> */ >>>> static int machine_kdump_pm_cb(struct notifier_block *nb, unsigned long action, >>>> @@ -43,12 +89,12 @@ static int machine_kdump_pm_cb(struct notifier_block *nb, unsigned long action, >>>> switch (action) { >>>> case PM_SUSPEND_PREPARE: >>>> case PM_HIBERNATION_PREPARE: >>>> - if (crashk_res.start) >>>> + if (kexec_crash_image) >>>> crash_map_reserved_pages(); >>>> break; >>>> case PM_POST_SUSPEND: >>>> case PM_POST_HIBERNATION: >>>> - if (crashk_res.start) >>>> + if (kexec_crash_image) >>>> crash_unmap_reserved_pages(); >>>> break; >>>> default: >>>> @@ -147,42 +193,6 @@ static int kdump_csum_valid(struct kimage *image) >>>> } >>>> >>>> /* >>>> - * Map or unmap crashkernel memory >>>> - */ >>>> -static void crash_map_pages(int enable) >>>> -{ >>>> - unsigned long size = resource_size(&crashk_res); >>>> - >>>> - BUG_ON(crashk_res.start % KEXEC_CRASH_MEM_ALIGN || >>>> - size % KEXEC_CRASH_MEM_ALIGN); >>>> - if (enable) >>>> - vmem_add_mapping(crashk_res.start, size); >>>> - else { >>>> - vmem_remove_mapping(crashk_res.start, size); >>>> - if (size) >>>> - os_info_crashkernel_add(crashk_res.start, size); >>>> - else >>>> - os_info_crashkernel_add(0, 0); >>>> - } >>>> -} >>>> - >>>> -/* >>>> - * Map crashkernel memory >>>> - */ >>>> -void crash_map_reserved_pages(void) >>>> -{ >>>> - crash_map_pages(1); >>>> -} >>>> - >>>> -/* >>>> - * Unmap crashkernel memory >>>> - */ >>>> -void crash_unmap_reserved_pages(void) >>>> -{ >>>> - crash_map_pages(0); >>>> -} >>>> - >>>> -/* >>>> * Give back memory to hypervisor before new kdump is loaded >>>> */ >>>> static int machine_kexec_prepare_kdump(void) >>>> diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c >>>> index d3f9688..5f00437 100644 >>>> --- a/arch/s390/kernel/setup.c >>>> +++ b/arch/s390/kernel/setup.c >>>> @@ -603,7 +603,7 @@ static void __init reserve_crashkernel(void) >>>> crashk_res.start = crash_base; >>>> crashk_res.end = crash_base + crash_size - 1; >>>> insert_resource(&iomem_resource, &crashk_res); >>>> - memblock_remove(crash_base, crash_size); >>>> + memblock_reserve(crash_base, crash_size); >>>> pr_info("Reserving %lluMB of memory at %lluMB " >>>> "for crashkernel (System RAM: %luMB)\n", >>>> crash_size >> 20, crash_base >> 20, >>>> @@ -871,7 +871,6 @@ void __init setup_arch(char **cmdline_p) >>>> setup_memory(); >>>> >>>> check_initrd(); >>>> - reserve_crashkernel(); >>>> #ifdef CONFIG_CRASH_DUMP >>>> /* >>>> * Be aware that smp_save_dump_cpus() triggers a system reset. >>>> @@ -890,7 +889,9 @@ void __init setup_arch(char **cmdline_p) >>>> /* >>>> * Create kernel page tables and switch to virtual addressing. >>>> */ >>>> - paging_init(); >>>> + paging_init(); >>>> + >>>> + reserve_crashkernel(); >>>> >>>> /* Setup default console */ >>>> conmode_default(); >>>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h >>>> index f82d6a2..c76641c 100644 >>>> --- a/include/linux/kexec.h >>>> +++ b/include/linux/kexec.h >>>> @@ -230,8 +230,6 @@ extern void crash_kexec(struct pt_regs *); >>>> int kexec_should_crash(struct task_struct *); >>>> void crash_save_cpu(struct pt_regs *regs, int cpu); >>>> void crash_save_vmcoreinfo(void); >>>> -void crash_map_reserved_pages(void); >>>> -void crash_unmap_reserved_pages(void); >>>> void arch_crash_save_vmcoreinfo(void); >>>> __printf(1, 2) >>>> void vmcoreinfo_append_str(const char *fmt, ...); >>>> diff --git a/kernel/kexec.c b/kernel/kexec.c >>>> index b73dc21..4384672 100644 >>>> --- a/kernel/kexec.c >>>> +++ b/kernel/kexec.c >>>> @@ -136,9 +136,6 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, >>>> if (ret) >>>> return ret; >>>> >>>> - if (flags & KEXEC_ON_CRASH) >>>> - crash_map_reserved_pages(); >>>> - >>>> if (flags & KEXEC_PRESERVE_CONTEXT) >>>> image->preserve_context = 1; >>>> >>>> @@ -161,12 +158,6 @@ out: >>>> if ((flags & KEXEC_ON_CRASH) && kexec_crash_image) >>>> arch_kexec_protect_crashkres(); >>>> >>>> - /* >>>> - * Once the reserved memory is mapped, we should unmap this memory >>>> - * before returning >>>> - */ >>>> - if (flags & KEXEC_ON_CRASH) >>>> - crash_unmap_reserved_pages(); >>>> kimage_free(image); >>>> return ret; >>>> } >>>> @@ -232,9 +223,6 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, >>>> >>>> result = do_kexec_load(entry, nr_segments, segments, flags); >>>> >>>> - if ((flags & KEXEC_ON_CRASH) && kexec_crash_image) >>>> - arch_kexec_protect_crashkres(); >>>> - >>>> mutex_unlock(&kexec_mutex); >>>> >>>> return result; >>>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c >>>> index f826e11..58cd872 100644 >>>> --- a/kernel/kexec_core.c >>>> +++ b/kernel/kexec_core.c >>>> @@ -953,7 +953,6 @@ int crash_shrink_memory(unsigned long new_size) >>>> start = roundup(start, KEXEC_CRASH_MEM_ALIGN); >>>> end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN); >>>> >>>> - crash_map_reserved_pages(); >>>> crash_free_reserved_phys_range(end, crashk_res.end); >>>> >>>> if ((start == end) && (crashk_res.parent != NULL)) >>>> @@ -967,7 +966,6 @@ int crash_shrink_memory(unsigned long new_size) >>>> crashk_res.end = end - 1; >>>> >>>> insert_resource(&iomem_resource, ram_res); >>>> - crash_unmap_reserved_pages(); >>>> >>>> unlock: >>>> mutex_unlock(&kexec_mutex); >>>> @@ -1549,17 +1547,12 @@ int kernel_kexec(void) >>>> } >>>> >>>> /* >>>> - * Add and remove page tables for crashkernel memory >>>> + * Protection mechanism for crashkernel reserved memory after >>>> + * the kdump kernel is loaded. >>>> * >>>> * Provide an empty default implementation here -- architecture >>>> * code may override this >>>> */ >>>> -void __weak crash_map_reserved_pages(void) >>>> -{} >>>> - >>>> -void __weak crash_unmap_reserved_pages(void) >>>> -{} >>>> - >>>> void __weak arch_kexec_protect_crashkres(void) >>>> {} >>>> >>>> -- >>>> 1.8.3.1 >>>> >>>> >>>> _______________________________________________ >>>> 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 > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec