Re: [PATCH] s390/kexec: Consolidate crash_map/unmap_reserved_pages() and arch_kexec_protect(unprotect)_crashkres()
From: Minfei Huang
Date: Wed Mar 30 2016 - 22:38:43 EST
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.
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@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Xunlei Pang <xlpang@xxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxxxxxxxxxxx
> > http://lists.infradead.org/mailman/listinfo/kexec
>
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