[PATCH 2/5] arm64: kdump: Support crashkernel=X fall back to reserve region above DMA zones

From: Zhen Lei <thunder.leizhen@huawei.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	<x86@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	<devicetree@vger.kernel.org>, Dave Young <dyoung@redhat.com>,
	Baoquan He <bhe@redhat.com>, Vivek Goyal <vgoyal@redhat.com>,
	<kexec@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	Jonathan Corbet <corbet@lwn.net>, <linux-doc@vger.kernel.org>
Cc: Zhen Lei <thunder.leizhen@huawei.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	Feng Zhou <zhoufeng.zf@bytedance.com>,
	Kefeng Wang <wangkefeng.wang@huawei.com>,
	Chen Zhou <dingguo.cz@antgroup.com>,
	"John Donnelly" <John.p.donnelly@oracle.com>,
	Dave Kleikamp <dave.kleikamp@oracle.com>
Subject: [PATCH 2/5] arm64: kdump: Support crashkernel=X fall back to reserve region above DMA zones
Date: Mon, 13 Jun 2022 16:09:29 +0800	[thread overview]
Message-ID: <20220613080932.663-3-thunder.leizhen@huawei.com> (raw)
In-Reply-To: <20220613080932.663-1-thunder.leizhen@huawei.com>

For crashkernel=X without '@offset', select a region within DMA zones
first, and fall back to reserve region above DMA zones. This allows
users to use the same configuration on multiple platforms.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  2 +-
 arch/arm64/mm/init.c                            | 16 +++++++++++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 61b179232b68001..fdac18beba5624e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -823,7 +823,7 @@
 			memory region [offset, offset + size] for that kernel
 			image. If '@offset' is omitted, then a suitable offset
 			is selected automatically.
-			[KNL, X86-64] Select a region under 4G first, and
+			[KNL, X86-64, ARM64] Select a region under 4G first, and
 			fall back to reserve region above 4G when '@offset'
 			hasn't been specified.
 			See Documentation/admin-guide/kdump/kdump.rst for further details.
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 5390f361208ccf7..8539598f9e58b4d 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -138,6 +138,7 @@ static void __init reserve_crashkernel(void)
 	unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
 	char *cmdline = boot_command_line;
 	int ret;
+	bool fixed_base;
 
 	if (!IS_ENABLED(CONFIG_KEXEC_CORE))
 		return;
@@ -166,15 +167,28 @@ static void __init reserve_crashkernel(void)
 		return;
 	}
 
+	fixed_base = !!crash_base;
 	crash_size = PAGE_ALIGN(crash_size);
 
 	/* User specifies base address explicitly. */
-	if (crash_base)
+	if (fixed_base)
 		crash_max = crash_base + crash_size;
 
+retry:
 	crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
 					       crash_base, crash_max);
 	if (!crash_base) {
+		/*
+		 * Attempt to fully allocate low memory failed, fall back
+		 * to high memory, the minimum required low memory will be
+		 * reserved later.
+		 */
+		if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) {
+			crash_max = CRASH_ADDR_HIGH_MAX;
+			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
+			goto retry;
+		}
+
 		pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
 			crash_size);
 		return;
-- 
2.25.1

