arm64: kdump: Support crashkernel=X fall back to reserve region above DMA zones

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>
Acked-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20221116121044.1690-3-thunder.leizhen@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6c6fafc3fba9bb52ddd6ecdd9c3b0d26c03eed97..9d458dfbec5f196595589292e4a581b3d9705f5c 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -831,7 +831,7 @@
                        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 ba7227179822d10a9a2ab3aff2519ae10886d39e..58a0bb2c17f18cf53d680333ac1936d1ceacf1e7 100644 (file)
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -132,6 +132,7 @@ 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 = false;
 
        if (!IS_ENABLED(CONFIG_KEXEC_CORE))
                return;
@@ -163,12 +164,26 @@ static void __init reserve_crashkernel(void)
        crash_size = PAGE_ALIGN(crash_size);
 
        /* User specifies base address explicitly. */
-       if (crash_base)
+       if (crash_base) {
+               fixed_base = true;
                crash_max = crash_base + crash_size;
+       }
 
+retry:
        crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
                                               crash_base, crash_max);
        if (!crash_base) {
+               /*
+                * If the first attempt was for low memory, 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;