linux-kernel - [PATCH 2/4] kdump: implement reserve_crashkernel

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Message-ID: <ZWEASEz37xE2Cmb5@dwarf.suse.cz>
Date:   Fri, 24 Nov 2023 20:58:00 +0100
From:   Jiri Bohac <jbohac@...e.cz>
To:     Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        Dave Young <dyoung@...hat.com>, kexec@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, mhocko@...e.cz
Subject: [PATCH 2/4] kdump: implement reserve_crashkernel_cma

reserve_crashkernel_cma() reserves CMA ranges for the
crash kernel. If allocating the requested size fails, 
try to reserve in smaller pieces.

Store the reserved ranges in the crashk_cma_ranges array
and the number of ranges in crashk_cma_cnt.

Signed-off-by: Jiri Bohac <jbohac@...e.cz>

---
 include/linux/crash_core.h |  9 +++++++
 kernel/crash_core.c        | 52 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index f1edefcf7377..5afe3866d35a 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -14,6 +14,13 @@
 extern struct resource crashk_res;
 extern struct resource crashk_low_res;
 
+extern struct range crashk_cma_ranges[];
+#ifdef CONFIG_CMA
+extern int crashk_cma_cnt;
+#else
+#define crashk_cma_cnt 0
+#endif
+
 #define CRASH_CORE_NOTE_NAME	   "CORE"
 #define CRASH_CORE_NOTE_HEAD_BYTES ALIGN(sizeof(struct elf_note), 4)
 #define CRASH_CORE_NOTE_NAME_BYTES ALIGN(sizeof(CRASH_CORE_NOTE_NAME), 4)
@@ -98,6 +105,8 @@ int __init parse_crashkernel(char *cmdline, unsigned long long system_ram,
 		unsigned long long *low_size, unsigned long long *cma_size,
 		bool *high);
 
+void __init reserve_crashkernel_cma(unsigned long long cma_size);
+
 #ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
 #ifndef DEFAULT_CRASH_KERNEL_LOW_SIZE
 #define DEFAULT_CRASH_KERNEL_LOW_SIZE	(128UL << 20)
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 1e952d2e451b..d71ecd59f16b 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -15,6 +15,7 @@
 #include <linux/memblock.h>
 #include <linux/kexec.h>
 #include <linux/kmemleak.h>
+#include <linux/cma.h>
 
 #include <asm/page.h>
 #include <asm/sections.h>
@@ -475,6 +476,57 @@ void __init reserve_crashkernel_generic(char *cmdline,
 }
 #endif
 
+#ifdef CONFIG_CMA
+#define CRASHKERNEL_CMA_RANGES_MAX 4
+
+struct range crashk_cma_ranges[CRASHKERNEL_CMA_RANGES_MAX];
+int crashk_cma_cnt = 0;
+
+void __init reserve_crashkernel_cma(unsigned long long cma_size)
+{
+	unsigned long long request_size = roundup(cma_size, PAGE_SIZE);
+	unsigned long long reserved_size = 0;
+
+	while (cma_size > reserved_size &&
+	       crashk_cma_cnt < CRASHKERNEL_CMA_RANGES_MAX) {
+
+		struct cma *res;
+
+		if (cma_declare_contiguous(0, request_size, 0, 0, 0, false,
+				       "crashkernel", &res)) {
+			/* reservation failed, try half-sized blocks */
+			if (request_size <= PAGE_SIZE)
+				break;
+
+			request_size = roundup(request_size / 2, PAGE_SIZE);
+			continue;
+		}
+
+		crashk_cma_ranges[crashk_cma_cnt].start = cma_get_base(res);
+		crashk_cma_ranges[crashk_cma_cnt].end =
+			crashk_cma_ranges[crashk_cma_cnt].start +
+			cma_get_size(res) - 1;
+		++crashk_cma_cnt;
+		reserved_size += request_size;
+	}
+
+	if (cma_size > reserved_size)
+		pr_warn("crashkernel CMA reservation failed: %lld MB requested, %lld MB reserved in %d ranges\n",
+			cma_size >> 20, reserved_size >> 20, crashk_cma_cnt);
+	else
+		pr_info("crashkernel CMA reserved: %lld MB in %d ranges\n",
+			reserved_size >> 20, crashk_cma_cnt);
+}
+
+#else /* CONFIG_CMA */
+struct range crashk_cma_ranges[0];
+void __init reserve_crashkernel_cma(unsigned long long cma_size)
+{
+	if (cma_size)
+		pr_warn("crashkernel CMA reservation failed: CMA disabled\n");
+}
+#endif
+
 int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
 			  void **addr, unsigned long *sz)
 {

-- 
Jiri Bohac <jbohac@...e.cz>
SUSE Labs, Prague, Czechia