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

[Borislav Petkov]

On Wed, Oct 14, 2015 at 10:43:28AM +0200, Joerg Roedel wrote:
> Reviewed-by: Joerg Roedel <jroedel@xxxxxxx>
> 
> 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@xxxxxxxxxx>
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@xxxxxxxxxx>
Reviewed-by: Joerg Roedel <jroedel@xxxxxxx>
Tested-by: Joerg Roedel <jroedel@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: jerry_hoemann@xxxxxx
Cc: Jiri Kosina <jkosina@xxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Mark Salter <msalter@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: WANG Chao <chaowang@xxxxxxxxxx>
Cc: x86-ml <x86@xxxxxxxxxx>
Cc: yinghai@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1443065091-28198-1-git-send-email-bhe@xxxxxxxxxx
[ 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 ImendÃrffer, Jane Smithard, Graham Norton, HRB 21284 (AG NÃrnberg)
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