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Subject[PATCH 2/2] arm64: mm: support bootparam max_addr
Date
From: Peng Fan <peng.fan@nxp.com>

There is a "mem=[x]" boot parameter, but when there is a whole reserved
by secure TEE, the continuous DRAM area is split with two memblocks.

For example, DRAM area [0x40000000, 0xffffffff], when TEE uses
[0x50000000, 0x51000000), the memblock will be split into
[0x40000000, 0x50000000) and [0x51000000, 0xffffffff].

If pass "mem=1024MB", the actually max addr will be 0x81000000.
However if need the max addr be 0x80000000, mem=1008MB should be used.

There also might be multiple other holes that no visible to Linux, when
we wanna to limit the max addr usable by Linux, using "max_addr=[X]" is
much easier than "mem=[X]"

Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
arch/arm64/mm/init.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index db63cc885771..3364b5e7a7fe 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -173,6 +173,7 @@ int pfn_is_map_memory(unsigned long pfn)
EXPORT_SYMBOL(pfn_is_map_memory);

static phys_addr_t memory_limit __ro_after_init = PHYS_ADDR_MAX;
+static phys_addr_t max_addr __ro_after_init = PHYS_ADDR_MAX;

/*
* Limit the memory size that was specified via FDT.
@@ -189,6 +190,18 @@ static int __init early_mem(char *p)
}
early_param("mem", early_mem);

+static int __init set_max_addr(char *p)
+{
+ if (!p)
+ return 1;
+
+ max_addr = memparse(p, &p) & PAGE_MASK;
+ pr_notice("Memory max addr set to 0x%llx\n", max_addr);
+
+ return 0;
+}
+early_param("max_addr", set_max_addr);
+
void __init arm64_memblock_init(void)
{
s64 linear_region_size = PAGE_END - _PAGE_OFFSET(vabits_actual);
@@ -253,6 +266,9 @@ void __init arm64_memblock_init(void)
memblock_add(__pa_symbol(_text), (u64)(_end - _text));
}

+ if (max_addr != PHYS_ADDR_MAX)
+ memblock_cap_memory_range(0, max_addr);
+
if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
/*
* Add back the memory we just removed if it results in the
@@ -427,4 +443,9 @@ void dump_mem_limit(void)
} else {
pr_emerg("Memory Limit: none\n");
}
+
+ if (max_addr != PHYS_ADDR_MAX)
+ pr_emerg("Max addr: 0x%llx\n", max_addr);
+ else
+ pr_emerg("Max addr: none\n");
}
--
2.25.1
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