linux-kernel - [PATCH v2 2/5] kdump: implement reserve_crashkernel

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Message-ID: <Z7dd0_XLzmb1tBUk@dwarf.suse.cz>
Date: Thu, 20 Feb 2025 17:52:35 +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: Philipp Rudo <prudo@...hat.com>, Donald Dutile <ddutile@...hat.com>,
	Pingfan Liu <piliu@...hat.com>, Tao Liu <ltao@...hat.com>,
	linux-kernel@...r.kernel.org,
	David Hildenbrand <dhildenb@...hat.com>,
	Michal Hocko <mhocko@...e.cz>
Subject: [PATCH v2 2/5] 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 blocks.

Store the reserved ranges in the crashk_cma_ranges array
and the number of ranges in crashk_cma_cnt.
---
 include/linux/crash_reserve.h | 12 +++++++++
 kernel/crash_reserve.c        | 49 +++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/include/linux/crash_reserve.h b/include/linux/crash_reserve.h
index a681f265a361..97964f2a583d 100644
--- a/include/linux/crash_reserve.h
+++ b/include/linux/crash_reserve.h
@@ -13,12 +13,24 @@
  */
 extern struct resource crashk_res;
 extern struct resource crashk_low_res;
+extern struct range crashk_cma_ranges[];
+#if defined(CONFIG_CMA) && defined(CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION)
+#define CRASHKERNEL_CMA
+#define CRASHKERNEL_CMA_RANGES_MAX 4
+extern int crashk_cma_cnt;
+#else
+#define crashk_cma_cnt 0
+#define CRASHKERNEL_CMA_RANGES_MAX 0
+#endif
+
 
 int __init parse_crashkernel(char *cmdline, unsigned long long system_ram,
 		unsigned long long *crash_size, unsigned long long *crash_base,
 		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_reserve.c b/kernel/crash_reserve.c
index e72a9c897694..d71aff19a28d 100644
--- a/kernel/crash_reserve.c
+++ b/kernel/crash_reserve.c
@@ -14,6 +14,8 @@
 #include <linux/cpuhotplug.h>
 #include <linux/memblock.h>
 #include <linux/kmemleak.h>
+#include <linux/cma.h>
+#include <linux/crash_reserve.h>
 
 #include <asm/page.h>
 #include <asm/sections.h>
@@ -470,6 +472,53 @@ void __init reserve_crashkernel_generic(char *cmdline,
 #endif
 }
 
+struct range crashk_cma_ranges[CRASHKERNEL_CMA_RANGES_MAX];
+#ifdef CRASHKERNEL_CMA
+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 /* CRASHKERNEL_CMA */
+void __init reserve_crashkernel_cma(unsigned long long cma_size)
+{
+	if (cma_size)
+		pr_warn("crashkernel CMA reservation not supported\n");
+}
+#endif
+
 #ifndef HAVE_ARCH_ADD_CRASH_RES_TO_IOMEM_EARLY
 static __init int insert_crashkernel_resources(void)
 {

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