[PATCH 7/8] x86: kdump: use generic interface to simplify crashkernel reservation code

Baoquan He
2023-08-27T10:12:43Z

With the help of newly changed function parse_crashkernel() and
generic reserve_crashkernel_generic(), crashkernel reservation can be
simplified by steps:

1) Provide CRASH_ALIGN, CRASH_ADDR_LOW_MAX, CRASH_ADDR_HIGH_MAX and
DEFAULT_CRASH_KERNEL_LOW_SIZE in <asm/kexec.h>;

2) Add arch_reserve_crashkernel() to call parse_crashkernel() and
reserve_crashkernel_generic(), and do the ARCH specific work if
needed.

3) Add ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION Kconfig in
arch/x86/Kconfig.

When adding DEFAULT_CRASH_KERNEL_LOW_SIZE, add crash_low_size_default()
to calculate crashkernel low memory because x86_64 has special
requirement.

The old reserve_crashkernel_low() and reserve_crashkernel() can be
removed.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
arch/x86/Kconfig | 3 +
arch/x86/include/asm/kexec.h | 32 ++++++++
arch/x86/kernel/setup.c | 144 ++++-------------------------------
3 files changed, 51 insertions(+), 128 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e36261b4ea14..31515b3ef55b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2073,6 +2073,9 @@ config KEXEC_FILE
config ARCH_HAS_KEXEC_PURGATORY
def_bool KEXEC_FILE

+config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
+ def_bool CRASH_CORE
+
config KEXEC_SIG
bool "Verify kernel signature during kexec_file_load() syscall"
depends on KEXEC_FILE
diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index 5b77bbc28f96..84a7d1f6f153 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -66,6 +66,37 @@ struct kimage;
# define KEXEC_ARCH KEXEC_ARCH_X86_64
#endif

+/*
+ * --------- Crashkernel reservation ------------------------------
+ */
+
+/* 16M alignment for crash kernel regions */
+#define CRASH_ALIGN SZ_16M
+
+/*
+ * Keep the crash kernel below this limit.
+ *
+ * Earlier 32-bits kernels would limit the kernel to the low 512 MB range
+ * due to mapping restrictions.
+ *
+ * 64-bit kdump kernels need to be restricted to be under 64 TB, which is
+ * the upper limit of system RAM in 4-level paging mode. Since the kdump
+ * jump could be from 5-level paging to 4-level paging, the jump will fail if
+ * the kernel is put above 64 TB, and during the 1st kernel bootup there's
+ * no good way to detect the paging mode of the target kernel which will be
+ * loaded for dumping.
+ */
+
+#ifdef CONFIG_X86_32
+# define CRASH_ADDR_LOW_MAX SZ_512M
+# define CRASH_ADDR_HIGH_MAX SZ_512M
+#else
+# define CRASH_ADDR_LOW_MAX SZ_4G
+# define CRASH_ADDR_HIGH_MAX SZ_64T
+#endif
+
+# define DEFAULT_CRASH_KERNEL_LOW_SIZE crash_low_size_default()
+
/*
* This function is responsible for capturing register states if coming
* via panic otherwise just fix up the ss and sp if coming via kernel
@@ -209,6 +240,7 @@ typedef void crash_vmclear_fn(void);
extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
extern void kdump_nmi_shootdown_cpus(void);

+extern unsigned long crash_low_size_default(void);
#endif /* __ASSEMBLY__ */

#endif /* _ASM_X86_KEXEC_H */
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 382c66d2cf71..559a5c4141db 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -474,152 +474,40 @@ static void __init memblock_x86_reserve_range_setup_data(void)
/*
* --------- Crashkernel reservation ------------------------------
*/
-
-/* 16M alignment for crash kernel regions */
-#define CRASH_ALIGN SZ_16M
-
-/*
- * Keep the crash kernel below this limit.
- *
- * Earlier 32-bits kernels would limit the kernel to the low 512 MB range
- * due to mapping restrictions.
- *
- * 64-bit kdump kernels need to be restricted to be under 64 TB, which is
- * the upper limit of system RAM in 4-level paging mode. Since the kdump
- * jump could be from 5-level paging to 4-level paging, the jump will fail if
- * the kernel is put above 64 TB, and during the 1st kernel bootup there's
- * no good way to detect the paging mode of the target kernel which will be
- * loaded for dumping.
- */
-#ifdef CONFIG_X86_32
-# define CRASH_ADDR_LOW_MAX SZ_512M
-# define CRASH_ADDR_HIGH_MAX SZ_512M
-#else
-# define CRASH_ADDR_LOW_MAX SZ_4G
-# define CRASH_ADDR_HIGH_MAX SZ_64T
-#endif
-
-static int __init reserve_crashkernel_low(void)
+unsigned long crash_low_size_default(void)
{
#ifdef CONFIG_X86_64
- unsigned long long base, low_base = 0, low_size = 0;
- unsigned long low_mem_limit;
- int ret;
-
- low_mem_limit = min(memblock_phys_mem_size(), CRASH_ADDR_LOW_MAX);
-
- /* crashkernel=Y,low */
- ret = parse_crashkernel_low(boot_command_line, low_mem_limit, &low_size, &base);
- if (ret) {
- /*
- * two parts from kernel/dma/swiotlb.c:
- * -swiotlb size: user-specified with swiotlb= or default.
- *
- * -swiotlb overflow buffer: now hardcoded to 32k. We round it
- * to 8M for other buffers that may need to stay low too. Also
- * make sure we allocate enough extra low memory so that we
- * don't run out of DMA buffers for 32-bit devices.
- */
- low_size = max(swiotlb_size_or_default() + (8UL << 20), 256UL << 20);
- } else {
- /* passed with crashkernel=0,low ? */
- if (!low_size)
- return 0;
- }
-
- low_base = memblock_phys_alloc_range(low_size, CRASH_ALIGN, 0, CRASH_ADDR_LOW_MAX);
- if (!low_base) {
- pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
- (unsigned long)(low_size >> 20));
- return -ENOMEM;
- }
-
- pr_info("Reserving %ldMB of low memory at %ldMB for crashkernel (low RAM limit: %ldMB)\n",
- (unsigned long)(low_size >> 20),
- (unsigned long)(low_base >> 20),
- (unsigned long)(low_mem_limit >> 20));
-
- crashk_low_res.start = low_base;
- crashk_low_res.end = low_base + low_size - 1;
- insert_resource(&iomem_resource, &crashk_low_res);
-#endif
+ return max(swiotlb_size_or_default() + (8UL << 20), 256UL << 20);
+#else
return 0;
+#endif
}

-static void __init reserve_crashkernel(void)
+static void __init arch_reserve_crashkernel(void)
{
- unsigned long long crash_size, crash_base, total_mem;
+ unsigned long long crash_base, crash_size, low_size = 0;
+ char *cmdline = boot_command_line;
bool high = false;
int ret;

if (!IS_ENABLED(CONFIG_KEXEC_CORE))
return;

- total_mem = memblock_phys_mem_size();
-
- /* crashkernel=XM */
- ret = parse_crashkernel(boot_command_line, total_mem,
- &crash_size, &crash_base, NULL, NULL);
- if (ret != 0 || crash_size <= 0) {
- /* crashkernel=X,high */
- ret = parse_crashkernel_high(boot_command_line, total_mem,
- &crash_size, &crash_base);
- if (ret != 0 || crash_size <= 0)
- return;
- high = true;
- }
+ ret = parse_crashkernel(cmdline, memblock_phys_mem_size(),
+ &crash_size, &crash_base,
+ &low_size, &high);
+ if (ret)
+ return;

if (xen_pv_domain()) {
pr_info("Ignoring crashkernel for a Xen PV domain\n");
return;
}

- /* 0 means: find the address automatically */
- if (!crash_base) {
- /*
- * Set CRASH_ADDR_LOW_MAX upper bound for crash memory,
- * crashkernel=x,high reserves memory over 4G, also allocates
- * 256M extra low memory for DMA buffers and swiotlb.
- * But the extra memory is not required for all machines.
- * So try low memory first and fall back to high memory
- * unless "crashkernel=size[KMG],high" is specified.
- */
- if (!high)
- crash_base = memblock_phys_alloc_range(crash_size,
- CRASH_ALIGN, CRASH_ALIGN,
- CRASH_ADDR_LOW_MAX);
- if (!crash_base)
- crash_base = memblock_phys_alloc_range(crash_size,
- CRASH_ALIGN, CRASH_ALIGN,
- CRASH_ADDR_HIGH_MAX);
- if (!crash_base) {
- pr_info("crashkernel reservation failed - No suitable area found.\n");
- return;
- }
- } else {
- unsigned long long start;
-
- start = memblock_phys_alloc_range(crash_size, SZ_1M, crash_base,
- crash_base + crash_size);
- if (start != crash_base) {
- pr_info("crashkernel reservation failed - memory is in use.\n");
- return;
- }
- }
-
- if (crash_base >= (1ULL << 32) && reserve_crashkernel_low()) {
- memblock_phys_free(crash_base, crash_size);
- return;
- }
-
- pr_info("Reserving %ldMB of memory at %ldMB for crashkernel (System RAM: %ldMB)\n",
- (unsigned long)(crash_size >> 20),
- (unsigned long)(crash_base >> 20),
- (unsigned long)(total_mem >> 20));
+ reserve_crashkernel_generic(cmdline, crash_size, crash_base,
+ low_size, high);

- crashk_res.start = crash_base;
- crashk_res.end = crash_base + crash_size - 1;
- insert_resource(&iomem_resource, &crashk_res);
+ return;
}

static struct resource standard_io_resources[] = {
@@ -1231,7 +1119,7 @@ void __init setup_arch(char **cmdline_p)
* Reserve memory for crash kernel after SRAT is parsed so that it
* won't consume hotpluggable memory.
*/
- reserve_crashkernel();
+ arch_reserve_crashkernel();

memblock_find_dma_reserve();