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Message-ID: <56FC9EE7.7020506@redhat.com>
Date: Thu, 31 Mar 2016 11:52:07 +0800
From: Xunlei Pang <xpang@...hat.com>
To: Baoquan He <bhe@...hat.com>, Minfei Huang <mhuang@...hat.com>
Cc: Xunlei Pang <xlpang@...hat.com>, kexec@...ts.infradead.org,
linux-kernel@...r.kernel.org, ebiederm@...ssion.com,
akpm@...ux-foundation.org,
Michael Holzheu <holzheu@...ux.vnet.ibm.com>,
Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH] s390/kexec: Consolidate crash_map/unmap_reserved_pages()
and arch_kexec_protect(unprotect)_crashkres()
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 <holzheu@...ux.vnet.ibm.com>
>>>> Signed-off-by: Xunlei Pang <xlpang@...hat.com>
>>>> ---
>>>> 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@...ts.infradead.org
>>>> http://lists.infradead.org/mailman/listinfo/kexec
>>> _______________________________________________
>>> kexec mailing list
>>> kexec@...ts.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/kexec
> _______________________________________________
> kexec mailing list
> kexec@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
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