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Subject[PATCH v3 2/3] arm64: mm: Don't defer reserve_crashkernel() with dma_force_32bit
Date
ARM64 enable ZONE_DMA by default, and with ZONE_DMA crash kernel
memory reservation is delayed until DMA zone memory range size
initilazation performed in zone_sizes_init(), but for most platforms
use 32bit dma_zone_bits, so add dma_force_32bit kernel parameter
if ZONE_DMA enabled, and initialize arm64_dma_phys_limit to
max_zone_phys(32) in arm64_memblock_init() if dma_force_32bit
is setup, this could let the crash kernel reservation earlier,
and allows linear creation with block mapping.

Reviewed-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
arch/arm64/include/asm/kexec.h | 1 +
arch/arm64/mm/init.c | 43 +++++++++++++++++++++++++++-------
arch/arm64/mm/mmu.c | 4 ++--
3 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 9839bfc163d7..624865d1cc71 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -95,6 +95,7 @@ void cpu_soft_restart(unsigned long el2_switch, unsigned long entry,
unsigned long arg0, unsigned long arg1,
unsigned long arg2);
#endif
+bool crashkernel_early_reserve(void);

#define ARCH_HAS_KIMAGE_ARCH

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 897de41102d9..18b0031eadd0 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -35,6 +35,7 @@
#include <asm/boot.h>
#include <asm/fixmap.h>
#include <asm/kasan.h>
+#include <asm/kexec.h>
#include <asm/kernel-pgtable.h>
#include <asm/kvm_host.h>
#include <asm/memory.h>
@@ -66,7 +67,8 @@ EXPORT_SYMBOL(memstart_addr);
* depending on DMA memory zones configs (ZONE_DMA) --
*
* In absence of ZONE_DMA and ZONE_DMA32 configs arm64_dma_phys_limit
- * initialized here and if only with ZONE_DMA32 arm64_dma_phys_limit
+ * initialized here, and if only with ZONE_DMA32 or if with ZONE_DMA
+ * and dma_force_32bit kernel parameter, the arm64_dma_phys_limit is
* initialised to max_zone_phys(32). This lets early reservation of
* crash kernel memory which has a dependency on arm64_dma_phys_limit.
* Reserving memory early for crash kernel allows linear creation of block
@@ -91,6 +93,27 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit;
phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1;
#endif

+static bool __ro_after_init arm64_dma_force_32bit;
+#ifdef CONFIG_ZONE_DMA
+static int __init arm64_dma_force_32bit_setup(char *p)
+{
+ zone_dma_bits = 32;
+ arm64_dma_force_32bit = true;
+
+ return 0;
+}
+early_param("dma_force_32bit", arm64_dma_force_32bit_setup);
+#endif
+
+bool __init crashkernel_early_reserve(void)
+{
+ if (!IS_ENABLED(CONFIG_ZONE_DMA))
+ return true;
+ if (arm64_dma_force_32bit)
+ return true;
+ return false;
+}
+
/*
* reserve_crashkernel() - reserves memory for crash kernel
*
@@ -162,12 +185,14 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
{
unsigned long max_zone_pfns[MAX_NR_ZONES] = {0};
#ifdef CONFIG_ZONE_DMA
- unsigned int acpi_zone_dma_bits;
- unsigned int dt_zone_dma_bits;
+ if (!arm64_dma_force_32bit) {
+ unsigned int acpi_zone_dma_bits;
+ unsigned int dt_zone_dma_bits;

- acpi_zone_dma_bits = fls64(acpi_iort_dma_get_max_cpu_address());
- dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL));
- zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_zone_dma_bits);
+ acpi_zone_dma_bits = fls64(acpi_iort_dma_get_max_cpu_address());
+ dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL));
+ zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_zone_dma_bits);
+ }
arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
#endif
@@ -334,8 +359,8 @@ void __init arm64_memblock_init(void)

early_init_fdt_scan_reserved_mem();

- if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
- if (IS_ENABLED(CONFIG_ZONE_DMA32))
+ if (crashkernel_early_reserve()) {
+ if (IS_ENABLED(CONFIG_ZONE_DMA32) || arm64_dma_force_32bit)
arm64_dma_phys_limit = max_zone_phys(32);
reserve_crashkernel();
}
@@ -386,7 +411,7 @@ void __init bootmem_init(void)
* request_standard_resources() depends on crashkernel's memory being
* reserved, so do it here.
*/
- if (IS_ENABLED(CONFIG_ZONE_DMA))
+ if (!crashkernel_early_reserve())
reserve_crashkernel();

memblock_dump_all();
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 23734481318a..46b626025b78 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -529,7 +529,7 @@ static void __init map_mem(pgd_t *pgdp)

#ifdef CONFIG_KEXEC_CORE
if (crash_mem_map) {
- if (IS_ENABLED(CONFIG_ZONE_DMA))
+ if (!crashkernel_early_reserve())
flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
else if (crashk_res.end)
memblock_mark_nomap(crashk_res.start,
@@ -570,7 +570,7 @@ static void __init map_mem(pgd_t *pgdp)
* through /sys/kernel/kexec_crash_size interface.
*/
#ifdef CONFIG_KEXEC_CORE
- if (crash_mem_map && !IS_ENABLED(CONFIG_ZONE_DMA)) {
+ if (crash_mem_map && crashkernel_early_reserve()) {
if (crashk_res.end) {
__map_memblock(pgdp, crashk_res.start,
crashk_res.end + 1,
--
2.26.2
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