On 01/21/19 at 01:16pm, Pingfan Liu wrote: > People reported crashkernel=384M reservation failed on a high end server > with KASLR enabled. In that case there is enough free memory under 896M > but crashkernel reservation still fails intermittently. > > The situation is crashkernel reservation code only finds free region under > 896 MB with 128M aligned in case no ',high' being used. And KASLR could > break the first 896M into several parts randomly thus the failure happens. > User has no way to predict and make sure crashkernel=xM working unless > he/she use 'crashkernel=xM,high'. Since 'crashkernel=xM' is the most > common use case this issue is a serious bug. > > And we can't answer questions raised from customer: > 1) why it doesn't succeed to reserve 896 MB; > 2) what's wrong with memory region under 4G; > 3) why I have to add ',high', I only require 384 MB, not 3840 MB. > > This patch tries to get memory region from 896 MB firstly, then [896MB,4G], > finally above 4G. > > Dave Young sent the original post, and I just re-post it with commit log > improvement as his requirement. > http://lists.infradead.org/pipermail/kexec/2017-October/019571.html > There was an old discussion below (previously posted by Chao Wang): > https://lkml.org/lkml/2013/10/15/601 > > Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx> > Cc: Dave Young <dyoung@xxxxxxxxxx> > Cc: Baoquan He <bhe@xxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> > Cc: yinghai@xxxxxxxxxx, > Cc: vgoyal@xxxxxxxxxx > Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> > Cc: Borislav Petkov <bp@xxxxxxxxx> > Cc: x86@xxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx Looks good, ack. Acked-by: Baoquan He <bhe@xxxxxxxxxx> Thanks Baoquan > --- > v6 -> v7: commit log improvement > arch/x86/kernel/setup.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > index 3d872a5..fa62c81 100644 > --- a/arch/x86/kernel/setup.c > +++ b/arch/x86/kernel/setup.c > @@ -551,6 +551,22 @@ static void __init reserve_crashkernel(void) > high ? CRASH_ADDR_HIGH_MAX > : CRASH_ADDR_LOW_MAX, > crash_size, CRASH_ALIGN); > +#ifdef CONFIG_X86_64 > + /* > + * crashkernel=X reserve below 896M fails? Try below 4G > + */ > + if (!high && !crash_base) > + crash_base = memblock_find_in_range(CRASH_ALIGN, > + (1ULL << 32), > + crash_size, CRASH_ALIGN); > + /* > + * crashkernel=X reserve below 4G fails? Try MAXMEM > + */ > + if (!high && !crash_base) > + crash_base = memblock_find_in_range(CRASH_ALIGN, > + CRASH_ADDR_HIGH_MAX, > + crash_size, CRASH_ALIGN); > +#endif > if (!crash_base) { > pr_info("crashkernel reservation failed - No suitable area found.\n"); > return; > -- > 2.7.4 > _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
