[PATCH 1/2] riscv: Only initialize swiotlb when necessary

[PATCH 1/2] riscv: Only initialize swiotlb when necessary

[Kefeng Wang]

The SWIOTLB buffer is not needed unless the physical address space
is beyond the limit of dma, only initialize swiotlb when swiotlb_force
is true or not all system memory is DMA-able.

Also move the swiotlb_init() into mem_init().

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 arch/riscv/kernel/setup.c | 5 -----
 arch/riscv/mm/init.c      | 8 ++++++++
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 03901d3a8b02..0ccf5a1a250f 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -17,7 +17,6 @@
 #include <linux/of_fdt.h>
 #include <linux/of_platform.h>
 #include <linux/sched/task.h>
-#include <linux/swiotlb.h>
 #include <linux/smp.h>
 #include <linux/efi.h>
 #include <linux/crash_dump.h>
@@ -296,10 +295,6 @@ void __init setup_arch(char **cmdline_p)
 		protect_kernel_linear_mapping_text_rodata();
 	}
 
-#ifdef CONFIG_SWIOTLB
-	swiotlb_init(1);
-#endif
-
 #ifdef CONFIG_KASAN
 	kasan_init();
 #endif
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 4faf8bd157ea..17f2e1da2b3d 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -11,6 +11,7 @@
 #include <linux/memblock.h>
 #include <linux/initrd.h>
 #include <linux/swap.h>
+#include <linux/swiotlb.h>
 #include <linux/sizes.h>
 #include <linux/of_fdt.h>
 #include <linux/of_reserved_mem.h>
@@ -113,6 +114,13 @@ void __init mem_init(void)
 	BUG_ON(!mem_map);
 #endif /* CONFIG_FLATMEM */
 
+#ifdef CONFIG_SWIOTLB
+	if (swiotlb_force == SWIOTLB_FORCE ||
+	    max_pfn > PFN_DOWN(dma32_phys_limit))
+		swiotlb_init(1);
+	else
+		swiotlb_force = SWIOTLB_NO_FORCE;
+#endif
 	high_memory = (void *)(__va(PFN_PHYS(max_low_pfn)));
 	memblock_free_all();
 
-- 
2.18.0.huawei.25


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[PATCH 2/2] riscv: Add mem kernel parameter support

[Kefeng Wang]

The memblock_enforce_memory_limit() could change the memblock
range, so move the dram_end assignment after it in bootmem_init(),
then support mem= cmdline.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 arch/riscv/mm/init.c | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 17f2e1da2b3d..ce61510a08c0 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -127,19 +127,39 @@ void __init mem_init(void)
 	print_vm_layout();
 }
 
+/*
+ * The default maximal physical memory size is -PAGE_OFFSET,
+ * limit the memory size via mem.
+ */
+static phys_addr_t memory_limit = -PAGE_OFFSET;
+
+static int __init early_mem(char *p)
+{
+	u64 size;
+
+	if (!p)
+		return 1;
+
+	size = memparse(p, &p) & PAGE_MASK;
+	memory_limit = min_t(u64, size, memory_limit);
+
+	pr_notice("Memory limited to %lldMB\n", (u64)memory_limit >> 20);
+
+	return 0;
+}
+early_param("mem", early_mem);
+
 void __init setup_bootmem(void)
 {
 	phys_addr_t vmlinux_end = __pa_symbol(&_end);
 	phys_addr_t vmlinux_start = __pa_symbol(&_start);
-	phys_addr_t dram_end = memblock_end_of_DRAM();
 	phys_addr_t max_mapped_addr = __pa(~(ulong)0);
+	phys_addr_t dram_end;
 
 #ifdef CONFIG_XIP_KERNEL
 	vmlinux_start = __pa_symbol(&_sdata);
 #endif
-
-	/* The maximal physical memory size is -PAGE_OFFSET. */
-	memblock_enforce_memory_limit(-PAGE_OFFSET);
+	memblock_enforce_memory_limit(memory_limit);
 
 	/*
 	 * Reserve from the start of the kernel to the end of the kernel
@@ -154,6 +174,7 @@ void __init setup_bootmem(void)
 #endif
 	memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
 
+	dram_end = memblock_end_of_DRAM();
 	/*
 	 * memblock allocator is not aware of the fact that last 4K bytes of
 	 * the addressable memory can not be mapped because of IS_ERR_VALUE
-- 
2.18.0.huawei.25


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Re: [PATCH 2/2] riscv: Add mem kernel parameter support

[Palmer Dabbelt]

On Wed, 02 Jun 2021 01:55:17 PDT (-0700), wangkefeng.wang@huawei.com wrote:
> The memblock_enforce_memory_limit() could change the memblock
> range, so move the dram_end assignment after it in bootmem_init(),
> then support mem= cmdline.
>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>  arch/riscv/mm/init.c | 29 +++++++++++++++++++++++++----
>  1 file changed, 25 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 17f2e1da2b3d..ce61510a08c0 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -127,19 +127,39 @@ void __init mem_init(void)
>  	print_vm_layout();
>  }
>
> +/*
> + * The default maximal physical memory size is -PAGE_OFFSET,
> + * limit the memory size via mem.
> + */
> +static phys_addr_t memory_limit = -PAGE_OFFSET;
> +
> +static int __init early_mem(char *p)
> +{
> +	u64 size;
> +
> +	if (!p)
> +		return 1;
> +
> +	size = memparse(p, &p) & PAGE_MASK;
> +	memory_limit = min_t(u64, size, memory_limit);
> +
> +	pr_notice("Memory limited to %lldMB\n", (u64)memory_limit >> 20);
> +
> +	return 0;
> +}
> +early_param("mem", early_mem);
> +
>  void __init setup_bootmem(void)
>  {
>  	phys_addr_t vmlinux_end = __pa_symbol(&_end);
>  	phys_addr_t vmlinux_start = __pa_symbol(&_start);
> -	phys_addr_t dram_end = memblock_end_of_DRAM();
>  	phys_addr_t max_mapped_addr = __pa(~(ulong)0);
> +	phys_addr_t dram_end;
>
>  #ifdef CONFIG_XIP_KERNEL
>  	vmlinux_start = __pa_symbol(&_sdata);
>  #endif
> -
> -	/* The maximal physical memory size is -PAGE_OFFSET. */
> -	memblock_enforce_memory_limit(-PAGE_OFFSET);
> +	memblock_enforce_memory_limit(memory_limit);
>
>  	/*
>  	 * Reserve from the start of the kernel to the end of the kernel
> @@ -154,6 +174,7 @@ void __init setup_bootmem(void)
>  #endif
>  	memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
>
> +	dram_end = memblock_end_of_DRAM();
>  	/*
>  	 * memblock allocator is not aware of the fact that last 4K bytes of
>  	 * the addressable memory can not be mapped because of IS_ERR_VALUE

I'm not sure why, but this patch won't apply.  I've applied it manually, 
it's on for-next (along with the #1).

Thanks!

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