* [PATCHv6] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr
@ 2019-01-14 3:15 Pingfan Liu
2019-01-14 4:23 ` Randy Dunlap
0 siblings, 1 reply; 3+ messages in thread
From: Pingfan Liu @ 2019-01-14 3:15 UTC (permalink / raw)
To: kexec
Cc: linux-kernel, Pingfan Liu, Dave Young, Baoquan He, Andrew Morton,
Mike Rapoport, yinghai, vgoyal
People reported a bug on a high end server with many pcie devices, where
kernel bootup with crashkernel=384M, and kaslr is enabled. Even
though we still see much memory under 896 MB, the finding still failed
intermittently. Because currently we can only find region under 896 MB,
if w/0 ',high' specified. Then KASLR breaks 896 MB into several parts
randomly, and crashkernel reservation need be aligned to 128 MB, that's
why failure is found. It raises confusion to the end user that sometimes
crashkernel=X works while sometimes fails.
If want to make it succeed, customer can change kernel option to
"crashkernel=384M, high". Just this give "crashkernel=xx@yy" a very
limited space to behave even though its grammer looks more generic.
And we can't answer questions raised from customer that confidently:
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@gmail.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: yinghai@kernel.org,
Cc: vgoyal@redhat.com
---
v5 -> v6
discard bottom-up allocation, just repost dyoung's original patch with commit log improved
---
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCHv6] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr
2019-01-14 3:15 [PATCHv6] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr Pingfan Liu
@ 2019-01-14 4:23 ` Randy Dunlap
2019-01-15 8:03 ` Pingfan Liu
0 siblings, 1 reply; 3+ messages in thread
From: Randy Dunlap @ 2019-01-14 4:23 UTC (permalink / raw)
To: Pingfan Liu, kexec
Cc: linux-kernel, Dave Young, Baoquan He, Andrew Morton,
Mike Rapoport, yinghai, vgoyal
Hi,
Just fix a few of the commit log comments...
On 1/13/19 7:15 PM, Pingfan Liu wrote:
> People reported a bug on a high end server with many pcie devices, where
> kernel bootup with crashkernel=384M, and kaslr is enabled. Even
> though we still see much memory under 896 MB, the finding still failed
> intermittently. Because currently we can only find region under 896 MB,
> if w/0 ',high' specified. Then KASLR breaks 896 MB into several parts
if w/o
or preferably:
if without
> randomly, and crashkernel reservation need be aligned to 128 MB, that's
> why failure is found. It raises confusion to the end user that sometimes
> crashkernel=X works while sometimes fails.
> If want to make it succeed, customer can change kernel option to
> "crashkernel=384M, high". Just this give "crashkernel=xx@yy" a very
no space? just
"crashkernel=384M,high"
> limited space to behave even though its grammer looks more generic.
grammar
> And we can't answer questions raised from customer that confidently:
> 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@gmail.com>
> Cc: Dave Young <dyoung@redhat.com>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
> Cc: yinghai@kernel.org,
> Cc: vgoyal@redhat.com
> ---
> v5 -> v6
> discard bottom-up allocation, just repost dyoung's original patch with commit log improved
> ---
> 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;
>
ciao.
--
~Randy
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCHv6] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr
2019-01-14 4:23 ` Randy Dunlap
@ 2019-01-15 8:03 ` Pingfan Liu
0 siblings, 0 replies; 3+ messages in thread
From: Pingfan Liu @ 2019-01-15 8:03 UTC (permalink / raw)
To: Randy Dunlap
Cc: kexec, LKML, Dave Young, Baoquan He, Andrew Morton,
Mike Rapoport, Yinghai Lu, vgoyal
On Mon, Jan 14, 2019 at 12:24 PM Randy Dunlap <rdunlap@infradead.org> wrote:
>
> Hi,
>
> Just fix a few of the commit log comments...
>
> On 1/13/19 7:15 PM, Pingfan Liu wrote:
> > People reported a bug on a high end server with many pcie devices, where
> > kernel bootup with crashkernel=384M, and kaslr is enabled. Even
> > though we still see much memory under 896 MB, the finding still failed
> > intermittently. Because currently we can only find region under 896 MB,
> > if w/0 ',high' specified. Then KASLR breaks 896 MB into several parts
>
> if w/o
> or preferably:
> if without
>
> > randomly, and crashkernel reservation need be aligned to 128 MB, that's
> > why failure is found. It raises confusion to the end user that sometimes
> > crashkernel=X works while sometimes fails.
> > If want to make it succeed, customer can change kernel option to
> > "crashkernel=384M, high". Just this give "crashkernel=xx@yy" a very
>
> no space? just
> "crashkernel=384M,high"
>
> > limited space to behave even though its grammer looks more generic.
>
> grammar
>
Thanks for your review, will cc you in next version.
Regards,
Pingfan
> > And we can't answer questions raised from customer that confidently:
> > 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@gmail.com>
> > Cc: Dave Young <dyoung@redhat.com>
> > Cc: Baoquan He <bhe@redhat.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
> > Cc: yinghai@kernel.org,
> > Cc: vgoyal@redhat.com
> > ---
> > v5 -> v6
> > discard bottom-up allocation, just repost dyoung's original patch with commit log improved
> > ---
> > 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;
> >
>
> ciao.
> --
> ~Randy
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-01-14 3:15 [PATCHv6] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr Pingfan Liu
2019-01-14 4:23 ` Randy Dunlap
2019-01-15 8:03 ` Pingfan Liu
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