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Re: [PATCH] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

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  Re: [PATCH] Do not reserve crashkernel high memory if crashkernel  low memory reserving failed Joerg Roedel <jroedel@suse.de> - 2015-10-14 10:50 +0200
    Re: [PATCH] Do not reserve crashkernel high memory if crashkernel  low memory reserving failed Borislav Petkov <bp@suse.de> - 2015-10-14 12:50 +0200

#1246421 — Re: [PATCH] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

On Thu, Sep 24, 2015 at 11:24:51AM +0800, Baoquan He wrote:
> People reported that when allocating crashkernel memory using
> ",high" and ",low" syntax, there were cases where the reservation
> of the "high" portion succeeds, but the reservation of the "low"
> portion fails. Then kexec can load kdump kernel successfully, but
> the boot of kdump kernel fails as there's no low memory. This is
> because allocation of low memory for kdump kernel can fail on large
> systems for reasons. E.g it could be manually specified crashkernel
> low memory is too large to find in memblock region.
> 
> In this patch add return value for reserve_crashkernel_low. Then
> try to reserve crashkernel low memory after crashkernel high memory
> has been allocated. If crashkernel low memory reservation failed
> free crashkernel high memory and return. User can take measures
> when they found kdump kernel cann't be loaded successfully.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
> v1->v2:
>   Boris commented that error value EINVAL is negative, should
>   use "return -EINVAL".
> 
> v2->v3:
>   Yinghai pointed out that during memblock_reserve, we could double
>   the memblock reserve array. New memblock reserve could be overlapped
>   with range for crashkernel high. So we have to reserve crashkernel
>   high firstly, then free it if crashkernel low memory allocation
>   failed.
> 
> v3->v4:
>   Dave suggested using "return -ENOMEM" when low memory reservation
>   failed and printing failure message anyway.
> 
> v4->v5:
>   Andrew suggested changing the content of failure message and taking
>   higher severity KERN_ERR.
> 
>  arch/x86/kernel/setup.c | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)

Reviewed-by: Joerg Roedel <jroedel@suse.de>

The patch is also in SLES for some time now and was successfully tested
there.


	Joerg

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#1246509

On Wed, Oct 14, 2015 at 10:43:28AM +0200, Joerg Roedel wrote:
> Reviewed-by: Joerg Roedel <jroedel@suse.de>
> 
> The patch is also in SLES for some time now and was successfully tested
> there.

Thanks, I massaged it a bit and ended up applying this:

---
From: Baoquan He <bhe@redhat.com>
Date: Thu, 24 Sep 2015 11:24:51 +0800
Subject: [PATCH] x86/setup: Do not reserve crashkernel high memory if low
 reservation failed

People reported that when allocating crashkernel memory using the
",high" and ",low" syntax, there were cases where the reservation of the
high portion succeeds but the reservation of the low portion fails.

Then kexec can load the kdump kernel successfully, but booting the kdump
kernel fails as there's no low memory.

The low memory allocation for the kdump kernel can fail on large systems
for a couple of reasons. For example, the manually specified crashkernel
low memory can be too large and thus no adequate memblock region would
be found.

Therefore, we try to reserve low memory for the crash kernel *after*
the high memory portion has been allocated. If that fails, we free
crashkernel high memory too and return. The user can then take measures
accordingly.

Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Joerg Roedel <jroedel@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Young <dyoung@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: jerry_hoemann@hp.com
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Juergen Gross <jgross@suse.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: WANG Chao <chaowang@redhat.com>
Cc: x86-ml <x86@kernel.org>
Cc: yinghai@kernel.org
Link: http://lkml.kernel.org/r/1443065091-28198-1-git-send-email-bhe@redhat.com
[ Massage text. ]
Signed-off-by: 
---
 arch/x86/kernel/setup.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index fdb7f2a2d328..1b36839e41eb 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -493,7 +493,7 @@ static void __init memblock_x86_reserve_range_setup_data(void)
 # define CRASH_KERNEL_ADDR_HIGH_MAX	MAXMEM
 #endif
 
-static void __init reserve_crashkernel_low(void)
+static int __init reserve_crashkernel_low(void)
 {
 #ifdef CONFIG_X86_64
 	const unsigned long long alignment = 16<<20;	/* 16M */
@@ -522,17 +522,16 @@ static void __init reserve_crashkernel_low(void)
 	} else {
 		/* passed with crashkernel=0,low ? */
 		if (!low_size)
-			return;
+			return 0;
 	}
 
 	low_base = memblock_find_in_range(low_size, (1ULL<<32),
 					low_size, alignment);
 
 	if (!low_base) {
-		if (!auto_set)
-			pr_info("crashkernel low reservation failed - No suitable area found.\n");
-
-		return;
+		pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
+		       (unsigned long)(low_size >> 20));
+		return -ENOMEM;
 	}
 
 	memblock_reserve(low_base, low_size);
@@ -544,6 +543,7 @@ static void __init reserve_crashkernel_low(void)
 	crashk_low_res.end   = low_base + low_size - 1;
 	insert_resource(&iomem_resource, &crashk_low_res);
 #endif
+	return 0;
 }
 
 static void __init reserve_crashkernel(void)
@@ -595,6 +595,11 @@ static void __init reserve_crashkernel(void)
 	}
 	memblock_reserve(crash_base, crash_size);
 
+	if (crash_base >= (1ULL << 32) && reserve_crashkernel_low()) {
+		memblock_free(crash_base, crash_size);
+		return;
+	}
+
 	printk(KERN_INFO "Reserving %ldMB of memory at %ldMB "
 			"for crashkernel (System RAM: %ldMB)\n",
 			(unsigned long)(crash_size >> 20),
@@ -604,9 +609,6 @@ 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);
-
-	if (crash_base >= (1ULL<<32))
-		reserve_crashkernel_low();
 }
 #else
 static void __init reserve_crashkernel(void)
-- 
2.3.5

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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