[PATCH -next 0/2] support allocating crashkernel above 4G explicitly on riscv

[PATCH -next 0/2] support allocating crashkernel above 4G explicitly on riscv

[Chen Jiahao]

On riscv, the current crash kernel allocation logic is trying to
allocate within 32bit addressible memory region by default, if
failed, try to allocate without 4G restriction.

In need of saving DMA zone memory while allocating a relatively large
crash kernel region, allocating the reserved memory top down in
high memory, without overlapping the DMA zone, is a mature solution.
Hence this patchset introduces the parameter option crashkernel=X,[high,low].

One can reserve the crash kernel from high memory above DMA zone range
by explicitly passing "crashkernel=X,high"; or reserve a memory range
below 4G with "crashkernel=X,low". Besides, there are few rules need
to take notice:
1. "crashkernel=X,[high,low]" will be ignored if "crashkernel=size"
   is specified.
2. "crashkernel=X,low" is valid only when "crashkernel=X,high" is passed
   and there is enough memory to be allocated under 4G.
3. When allocating crashkernel above 4G and no "crashkernel=X,low" is
   specified, a 128M low memory will be allocated automatically for
   swiotlb bounce buffer.
See Documentation/admin-guide/kernel-parameters.txt for more information.

Following test cases have been performed as expected:
1) crashkernel=256M                          //low=256M
2) crashkernel=1G                            //low=1G
3) crashkernel=4G                            //high=4G, low=128M(default)
4) crashkernel=4G crashkernel=256M,high      //high=4G, low=128M(default), high is ignored
5) crashkernel=4G crashkernel=256M,low       //high=4G, low=128M(default), low is ignored
6) crashkernel=4G,high                       //high=4G, low=128M(default)
7) crashkernel=256M,low                      //low=0M, invalid
8) crashkernel=4G,high crashkernel=256M,low  //high=4G, low=256M
9) crashkernel=4G,high crashkernel=4G,low    //high=0M, low=0M, invalid
10) crashkernel=512M@0xd0000000              //low=512M

Chen Jiahao (2):
  riscv: kdump: Implement crashkernel=X,[high,low]
  docs: kdump: Update the crashkernel description for riscv

 .../admin-guide/kernel-parameters.txt         | 15 ++---
 arch/riscv/kernel/setup.c                     |  5 ++
 arch/riscv/mm/init.c                          | 56 ++++++++++++++++++-
 3 files changed, 66 insertions(+), 10 deletions(-)

-- 
2.31.1

[PATCH -next 1/2] riscv: kdump: Implement crashkernel=X,[high,low]

[Chen Jiahao]

On riscv, the current crash kernel allocation logic is trying to
allocate within 32bit addressible memory region by default, if
failed, try to allocate without 4G restriction.

In need of saving DMA zone memory while allocating a relatively large
crash kernel region, allocating the reserved memory top down in
high memory, without overlapping the DMA zone, is a mature solution.
Here introduce the parameter option crashkernel=X,[high,low].

We can reserve the crash kernel from high memory above DMA zone range
by explicitly passing "crashkernel=X,high"; or reserve a memory range
below 4G with "crashkernel=X,low".

Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
---
 arch/riscv/kernel/setup.c |  5 ++++
 arch/riscv/mm/init.c      | 56 ++++++++++++++++++++++++++++++++++++---
 2 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 376d2827e736..d867b1535da4 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -176,6 +176,11 @@ static void __init init_resources(void)
 		if (ret < 0)
 			goto error;
 	}
+	if (crashk_low_res.start != crashk_low_res.end) {
+		ret = add_resource(&iomem_resource, &crashk_low_res);
+		if (ret < 0)
+			goto error;
+	}
 #endif
 
 #ifdef CONFIG_CRASH_DUMP
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 478d6763a01a..5def2174b243 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1152,6 +1152,28 @@ static inline void setup_vm_final(void)
 }
 #endif /* CONFIG_MMU */
 
+/* Reserve 128M low memory by default for swiotlb buffer */
+#define DEFAULT_CRASH_KERNEL_LOW_SIZE	(128UL << 20)
+
+static int __init reserve_crashkernel_low(unsigned long long low_size)
+{
+	unsigned long long low_base;
+
+	low_base = memblock_phys_alloc_range(low_size, PMD_SIZE, 0, dma32_phys_limit);
+	if (!low_base) {
+		pr_err("cannot allocate crashkernel low memory (size:0x%llx).\n", low_size);
+		return -ENOMEM;
+	}
+
+	pr_info("crashkernel low memory reserved: 0x%08llx - 0x%08llx (%lld MB)\n",
+		low_base, low_base + low_size, low_size >> 20);
+
+	crashk_low_res.start = low_base;
+	crashk_low_res.end = low_base + low_size - 1;
+
+	return 0;
+}
+
 /*
  * reserve_crashkernel() - reserves memory for crash kernel
  *
@@ -1163,6 +1185,7 @@ static void __init reserve_crashkernel(void)
 {
 	unsigned long long crash_base = 0;
 	unsigned long long crash_size = 0;
+	unsigned long long crash_low_size = 0;
 	unsigned long search_start = memblock_start_of_DRAM();
 	unsigned long search_end = memblock_end_of_DRAM();
 
@@ -1182,8 +1205,26 @@ static void __init reserve_crashkernel(void)
 
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 				&crash_size, &crash_base);
-	if (ret || !crash_size)
+	if (ret == -ENOENT) {
+		ret = parse_crashkernel_high(boot_command_line, 0, &crash_size, &crash_base);
+		if (ret || !crash_size)
+			return;
+
+		/*
+		 * crashkernel=Y,low can be specified or not, but invalid value
+		 * is not allowed.
+		 */
+		ret = parse_crashkernel_low(boot_command_line, 0, &crash_low_size, &crash_base);
+		if (ret == -ENOENT)
+			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
+		else if (ret)
+			return;
+
+		search_start = dma32_phys_limit;
+	} else if (ret || !crash_size) {
+		/* Invalid argument value specified */
 		return;
+	}
 
 	crash_size = PAGE_ALIGN(crash_size);
 
@@ -1201,16 +1242,25 @@ static void __init reserve_crashkernel(void)
 	 */
 	crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
 					       search_start,
-					       min(search_end, (unsigned long) SZ_4G));
+					       min(search_end, (unsigned long) dma32_phys_limit));
 	if (crash_base == 0) {
 		/* Try again without restricting region to 32bit addressible memory */
 		crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
-						search_start, search_end);
+						       search_start, search_end);
 		if (crash_base == 0) {
 			pr_warn("crashkernel: couldn't allocate %lldKB\n",
 				crash_size >> 10);
 			return;
 		}
+
+		if (!crash_low_size)
+			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
+	}
+
+	if ((crash_base > dma32_phys_limit - crash_low_size) &&
+	     crash_low_size && reserve_crashkernel_low(crash_low_size)) {
+		memblock_phys_free(crash_base, crash_size);
+		return;
 	}
 
 	pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n",
-- 
2.31.1

Re: [PATCH -next 1/2] riscv: kdump: Implement crashkernel=X,[high,low]

[Simon Horman]

On Tue, Mar 21, 2023 at 04:42:43AM +0800, Chen Jiahao wrote:
> On riscv, the current crash kernel allocation logic is trying to
> allocate within 32bit addressible memory region by default, if
> failed, try to allocate without 4G restriction.
> 
> In need of saving DMA zone memory while allocating a relatively large
> crash kernel region, allocating the reserved memory top down in
> high memory, without overlapping the DMA zone, is a mature solution.
> Here introduce the parameter option crashkernel=X,[high,low].
> 
> We can reserve the crash kernel from high memory above DMA zone range
> by explicitly passing "crashkernel=X,high"; or reserve a memory range
> below 4G with "crashkernel=X,low".
> 
> Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>

Some minor nits, but I don't think there is any need to respin for them.

Reviewed-by: Simon Horman <horms@kernel.org>

...

> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 478d6763a01a..5def2174b243 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c

...

> @@ -1201,16 +1242,25 @@ static void __init reserve_crashkernel(void)
>  	 */
>  	crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
>  					       search_start,
> -					       min(search_end, (unsigned long) SZ_4G));
> +					       min(search_end, (unsigned long) dma32_phys_limit));

nit: While here, you could drop the space before 'ma32_phys_limit'.
     Or perhaps use min_t, which seems appropriate here.

>  	if (crash_base == 0) {
>  		/* Try again without restricting region to 32bit addressible memory */
>  		crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
> -						search_start, search_end);
> +						       search_start, search_end);
>  		if (crash_base == 0) {
>  			pr_warn("crashkernel: couldn't allocate %lldKB\n",
>  				crash_size >> 10);
>  			return;
>  		}
> +
> +		if (!crash_low_size)
> +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> +	}
> +
> +	if ((crash_base > dma32_phys_limit - crash_low_size) &&
> +	     crash_low_size && reserve_crashkernel_low(crash_low_size)) {

nit: The line above should be aligned one character to the left
     (remove one space in the indent).

> +		memblock_phys_free(crash_base, crash_size);
> +		return;
>  	}
>  
>  	pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n",

...

Re: [PATCH -next 1/2] riscv: kdump: Implement crashkernel=X,[high,low]

[chenjiahao (C)]

On 2023/3/20 22:36, Simon Horman wrote:
> On Tue, Mar 21, 2023 at 04:42:43AM +0800, Chen Jiahao wrote:
>> On riscv, the current crash kernel allocation logic is trying to
>> allocate within 32bit addressible memory region by default, if
>> failed, try to allocate without 4G restriction.
>>
>> In need of saving DMA zone memory while allocating a relatively large
>> crash kernel region, allocating the reserved memory top down in
>> high memory, without overlapping the DMA zone, is a mature solution.
>> Here introduce the parameter option crashkernel=X,[high,low].
>>
>> We can reserve the crash kernel from high memory above DMA zone range
>> by explicitly passing "crashkernel=X,high"; or reserve a memory range
>> below 4G with "crashkernel=X,low".
>>
>> Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
> Some minor nits, but I don't think there is any need to respin for them.
>
> Reviewed-by: Simon Horman <horms@kernel.org>

I will send another version and clean up these by the way, thanks.

Chen, Jiahao


>
> ...
>
>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>> index 478d6763a01a..5def2174b243 100644
>> --- a/arch/riscv/mm/init.c
>> +++ b/arch/riscv/mm/init.c
> ...
>
>> @@ -1201,16 +1242,25 @@ static void __init reserve_crashkernel(void)
>>   	 */
>>   	crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
>>   					       search_start,
>> -					       min(search_end, (unsigned long) SZ_4G));
>> +					       min(search_end, (unsigned long) dma32_phys_limit));
> nit: While here, you could drop the space before 'ma32_phys_limit'.
>       Or perhaps use min_t, which seems appropriate here.
>
>>   	if (crash_base == 0) {
>>   		/* Try again without restricting region to 32bit addressible memory */
>>   		crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
>> -						search_start, search_end);
>> +						       search_start, search_end);
>>   		if (crash_base == 0) {
>>   			pr_warn("crashkernel: couldn't allocate %lldKB\n",
>>   				crash_size >> 10);
>>   			return;
>>   		}
>> +
>> +		if (!crash_low_size)
>> +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
>> +	}
>> +
>> +	if ((crash_base > dma32_phys_limit - crash_low_size) &&
>> +	     crash_low_size && reserve_crashkernel_low(crash_low_size)) {
> nit: The line above should be aligned one character to the left
>       (remove one space in the indent).
>
>> +		memblock_phys_free(crash_base, crash_size);
>> +		return;
>>   	}
>>   
>>   	pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n",
> ...

Re: [PATCH -next 1/2] riscv: kdump: Implement crashkernel=X,[high,low]

[Leizhen (ThunderTown)]

On 2023/3/21 4:42, Chen Jiahao wrote:
> On riscv, the current crash kernel allocation logic is trying to
> allocate within 32bit addressible memory region by default, if
> failed, try to allocate without 4G restriction.
> 
> In need of saving DMA zone memory while allocating a relatively large
> crash kernel region, allocating the reserved memory top down in
> high memory, without overlapping the DMA zone, is a mature solution.
> Here introduce the parameter option crashkernel=X,[high,low].
> 
> We can reserve the crash kernel from high memory above DMA zone range
> by explicitly passing "crashkernel=X,high"; or reserve a memory range
> below 4G with "crashkernel=X,low".
> 
> Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
> ---
>  arch/riscv/kernel/setup.c |  5 ++++
>  arch/riscv/mm/init.c      | 56 ++++++++++++++++++++++++++++++++++++---
>  2 files changed, 58 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index 376d2827e736..d867b1535da4 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -176,6 +176,11 @@ static void __init init_resources(void)
>  		if (ret < 0)
>  			goto error;
>  	}
> +	if (crashk_low_res.start != crashk_low_res.end) {
> +		ret = add_resource(&iomem_resource, &crashk_low_res);
> +		if (ret < 0)
> +			goto error;
> +	}
>  #endif
>  
>  #ifdef CONFIG_CRASH_DUMP
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 478d6763a01a..5def2174b243 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -1152,6 +1152,28 @@ static inline void setup_vm_final(void)
>  }
>  #endif /* CONFIG_MMU */
>  
> +/* Reserve 128M low memory by default for swiotlb buffer */
> +#define DEFAULT_CRASH_KERNEL_LOW_SIZE	(128UL << 20)
> +
> +static int __init reserve_crashkernel_low(unsigned long long low_size)
> +{
> +	unsigned long long low_base;
> +
> +	low_base = memblock_phys_alloc_range(low_size, PMD_SIZE, 0, dma32_phys_limit);
> +	if (!low_base) {
> +		pr_err("cannot allocate crashkernel low memory (size:0x%llx).\n", low_size);
> +		return -ENOMEM;
> +	}
> +
> +	pr_info("crashkernel low memory reserved: 0x%08llx - 0x%08llx (%lld MB)\n",

For unsigned long long, 08 --> 016.

> +		low_base, low_base + low_size, low_size >> 20);
> +
> +	crashk_low_res.start = low_base;
> +	crashk_low_res.end = low_base + low_size - 1;
> +
> +	return 0;
> +}
> +
>  /*
>   * reserve_crashkernel() - reserves memory for crash kernel
>   *
> @@ -1163,6 +1185,7 @@ static void __init reserve_crashkernel(void)
>  {
>  	unsigned long long crash_base = 0;
>  	unsigned long long crash_size = 0;
> +	unsigned long long crash_low_size = 0;
>  	unsigned long search_start = memblock_start_of_DRAM();
>  	unsigned long search_end = memblock_end_of_DRAM();
>  
> @@ -1182,8 +1205,26 @@ static void __init reserve_crashkernel(void)
>  
>  	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>  				&crash_size, &crash_base);
> -	if (ret || !crash_size)
> +	if (ret == -ENOENT) {
> +		ret = parse_crashkernel_high(boot_command_line, 0, &crash_size, &crash_base);
> +		if (ret || !crash_size)
> +			return;
> +
> +		/*
> +		 * crashkernel=Y,low can be specified or not, but invalid value
> +		 * is not allowed.
> +		 */
> +		ret = parse_crashkernel_low(boot_command_line, 0, &crash_low_size, &crash_base);
> +		if (ret == -ENOENT)
> +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> +		else if (ret)
> +			return;
> +
> +		search_start = dma32_phys_limit;
> +	} else if (ret || !crash_size) {
> +		/* Invalid argument value specified */
>  		return;
> +	}
>  
>  	crash_size = PAGE_ALIGN(crash_size);
>  
> @@ -1201,16 +1242,25 @@ static void __init reserve_crashkernel(void)
>  	 */
>  	crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
>  					       search_start,
> -					       min(search_end, (unsigned long) SZ_4G));
> +					       min(search_end, (unsigned long) dma32_phys_limit));
>  	if (crash_base == 0) {
>  		/* Try again without restricting region to 32bit addressible memory */
>  		crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
> -						search_start, search_end);
> +						       search_start, search_end);
>  		if (crash_base == 0) {
>  			pr_warn("crashkernel: couldn't allocate %lldKB\n",
>  				crash_size >> 10);
>  			return;
>  		}
> +
> +		if (!crash_low_size)
> +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> +	}
> +
> +	if ((crash_base > dma32_phys_limit - crash_low_size) &&
> +	     crash_low_size && reserve_crashkernel_low(crash_low_size)) {
> +		memblock_phys_free(crash_base, crash_size);
> +		return;
>  	}
>  
>  	pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n",
> 

-- 
Regards,
  Zhen Lei

Re: [PATCH -next 1/2] riscv: kdump: Implement crashkernel=X,[high,low]

[chenjiahao (C)]

On 2023/3/21 9:42, Leizhen (ThunderTown) wrote:
>
> On 2023/3/21 4:42, Chen Jiahao wrote:
>> On riscv, the current crash kernel allocation logic is trying to
>> allocate within 32bit addressible memory region by default, if
>> failed, try to allocate without 4G restriction.
>>
>> In need of saving DMA zone memory while allocating a relatively large
>> crash kernel region, allocating the reserved memory top down in
>> high memory, without overlapping the DMA zone, is a mature solution.
>> Here introduce the parameter option crashkernel=X,[high,low].
>>
>> We can reserve the crash kernel from high memory above DMA zone range
>> by explicitly passing "crashkernel=X,high"; or reserve a memory range
>> below 4G with "crashkernel=X,low".
>>
>> Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
>> ---
>>   arch/riscv/kernel/setup.c |  5 ++++
>>   arch/riscv/mm/init.c      | 56 ++++++++++++++++++++++++++++++++++++---
>>   2 files changed, 58 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
>> index 376d2827e736..d867b1535da4 100644
>> --- a/arch/riscv/kernel/setup.c
>> +++ b/arch/riscv/kernel/setup.c
>> @@ -176,6 +176,11 @@ static void __init init_resources(void)
>>   		if (ret < 0)
>>   			goto error;
>>   	}
>> +	if (crashk_low_res.start != crashk_low_res.end) {
>> +		ret = add_resource(&iomem_resource, &crashk_low_res);
>> +		if (ret < 0)
>> +			goto error;
>> +	}
>>   #endif
>>   
>>   #ifdef CONFIG_CRASH_DUMP
>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>> index 478d6763a01a..5def2174b243 100644
>> --- a/arch/riscv/mm/init.c
>> +++ b/arch/riscv/mm/init.c
>> @@ -1152,6 +1152,28 @@ static inline void setup_vm_final(void)
>>   }
>>   #endif /* CONFIG_MMU */
>>   
>> +/* Reserve 128M low memory by default for swiotlb buffer */
>> +#define DEFAULT_CRASH_KERNEL_LOW_SIZE	(128UL << 20)
>> +
>> +static int __init reserve_crashkernel_low(unsigned long long low_size)
>> +{
>> +	unsigned long long low_base;
>> +
>> +	low_base = memblock_phys_alloc_range(low_size, PMD_SIZE, 0, dma32_phys_limit);
>> +	if (!low_base) {
>> +		pr_err("cannot allocate crashkernel low memory (size:0x%llx).\n", low_size);
>> +		return -ENOMEM;
>> +	}
>> +
>> +	pr_info("crashkernel low memory reserved: 0x%08llx - 0x%08llx (%lld MB)\n",
> For unsigned long long, 08 --> 016.

Sure, I will fix it soon in another version.

>
>> +		low_base, low_base + low_size, low_size >> 20);
>> +
>> +	crashk_low_res.start = low_base;
>> +	crashk_low_res.end = low_base + low_size - 1;
>> +
>> +	return 0;
>> +}
>> +
>>   /*
>>    * reserve_crashkernel() - reserves memory for crash kernel
>>    *
>> @@ -1163,6 +1185,7 @@ static void __init reserve_crashkernel(void)
>>   {
>>   	unsigned long long crash_base = 0;
>>   	unsigned long long crash_size = 0;
>> +	unsigned long long crash_low_size = 0;
>>   	unsigned long search_start = memblock_start_of_DRAM();
>>   	unsigned long search_end = memblock_end_of_DRAM();
>>   
>> @@ -1182,8 +1205,26 @@ static void __init reserve_crashkernel(void)
>>   
>>   	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>>   				&crash_size, &crash_base);
>> -	if (ret || !crash_size)
>> +	if (ret == -ENOENT) {
>> +		ret = parse_crashkernel_high(boot_command_line, 0, &crash_size, &crash_base);
>> +		if (ret || !crash_size)
>> +			return;
>> +
>> +		/*
>> +		 * crashkernel=Y,low can be specified or not, but invalid value
>> +		 * is not allowed.
>> +		 */
>> +		ret = parse_crashkernel_low(boot_command_line, 0, &crash_low_size, &crash_base);
>> +		if (ret == -ENOENT)
>> +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
>> +		else if (ret)
>> +			return;
>> +
>> +		search_start = dma32_phys_limit;
>> +	} else if (ret || !crash_size) {
>> +		/* Invalid argument value specified */
>>   		return;
>> +	}
>>   
>>   	crash_size = PAGE_ALIGN(crash_size);
>>   
>> @@ -1201,16 +1242,25 @@ static void __init reserve_crashkernel(void)
>>   	 */
>>   	crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
>>   					       search_start,
>> -					       min(search_end, (unsigned long) SZ_4G));
>> +					       min(search_end, (unsigned long) dma32_phys_limit));
>>   	if (crash_base == 0) {
>>   		/* Try again without restricting region to 32bit addressible memory */
>>   		crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
>> -						search_start, search_end);
>> +						       search_start, search_end);
>>   		if (crash_base == 0) {
>>   			pr_warn("crashkernel: couldn't allocate %lldKB\n",
>>   				crash_size >> 10);
>>   			return;
>>   		}
>> +
>> +		if (!crash_low_size)
>> +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
>> +	}
>> +
>> +	if ((crash_base > dma32_phys_limit - crash_low_size) &&
>> +	     crash_low_size && reserve_crashkernel_low(crash_low_size)) {
>> +		memblock_phys_free(crash_base, crash_size);
>> +		return;
>>   	}
>>   
>>   	pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n",
>>
BR,

Chen, Jiahao

[PATCH -next 2/2] docs: kdump: Update the crashkernel description for riscv

[Chen Jiahao]

Now "crashkernel=" parameter on riscv has been updated to support
crashkernel=X,[high,low]. Through which we can reserve memory region
above/within 32bit addressible DMA zone.

Here update the parameter description accordingly.

Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6221a1d057dd..89e26a4864f8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -843,7 +843,7 @@
 			memory region [offset, offset + size] for that kernel
 			image. If '@offset' is omitted, then a suitable offset
 			is selected automatically.
-			[KNL, X86-64, ARM64] Select a region under 4G first, and
+			[KNL, X86-64, ARM64, RISCV] 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.
@@ -856,14 +856,14 @@
 			Documentation/admin-guide/kdump/kdump.rst for an example.
 
 	crashkernel=size[KMG],high
-			[KNL, X86-64, ARM64] range could be above 4G. Allow kernel
-			to allocate physical memory region from top, so could
-			be above 4G if system have more than 4G ram installed.
-			Otherwise memory region will be allocated below 4G, if
-			available.
+			[KNL, X86-64, ARM64, RISCV] range could be above 4G.
+			Allow kernel to allocate physical memory region from top,
+			so could be above 4G if system have more than 4G ram
+			installed. Otherwise memory region will be allocated
+			below 4G, if available.
 			It will be ignored if crashkernel=X is specified.
 	crashkernel=size[KMG],low
-			[KNL, X86-64, ARM64] range under 4G. When crashkernel=X,high
+			[KNL, X86-64, ARM64, RISCV] range under 4G. When crashkernel=X,high
 			is passed, kernel could allocate physical memory region
 			above 4G, that cause second kernel crash on system
 			that require some amount of low memory, e.g. swiotlb
@@ -874,6 +874,7 @@
 			size is	platform dependent.
 			  --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
 			  --> arm64: 128MiB
+			  --> riscv: 128MiB
 			This one lets the user specify own low range under 4G
 			for second kernel instead.
 			0: to disable low allocation.
-- 
2.31.1

Re: [PATCH -next 2/2] docs: kdump: Update the crashkernel description for riscv

[Simon Horman]

On Tue, Mar 21, 2023 at 04:42:44AM +0800, Chen Jiahao wrote:
> Now "crashkernel=" parameter on riscv has been updated to support
> crashkernel=X,[high,low]. Through which we can reserve memory region
> above/within 32bit addressible DMA zone.
> 
> Here update the parameter description accordingly.
> 
> Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH -next 2/2] docs: kdump: Update the crashkernel description for riscv

[Leizhen (ThunderTown)]

On 2023/3/21 4:42, Chen Jiahao wrote:
> Now "crashkernel=" parameter on riscv has been updated to support
> crashkernel=X,[high,low]. Through which we can reserve memory region
> above/within 32bit addressible DMA zone.
> 
> Here update the parameter description accordingly.

Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>

> 
> Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 6221a1d057dd..89e26a4864f8 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -843,7 +843,7 @@
>  			memory region [offset, offset + size] for that kernel
>  			image. If '@offset' is omitted, then a suitable offset
>  			is selected automatically.
> -			[KNL, X86-64, ARM64] Select a region under 4G first, and
> +			[KNL, X86-64, ARM64, RISCV] 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.
> @@ -856,14 +856,14 @@
>  			Documentation/admin-guide/kdump/kdump.rst for an example.
>  
>  	crashkernel=size[KMG],high
> -			[KNL, X86-64, ARM64] range could be above 4G. Allow kernel
> -			to allocate physical memory region from top, so could
> -			be above 4G if system have more than 4G ram installed.
> -			Otherwise memory region will be allocated below 4G, if
> -			available.
> +			[KNL, X86-64, ARM64, RISCV] range could be above 4G.
> +			Allow kernel to allocate physical memory region from top,
> +			so could be above 4G if system have more than 4G ram
> +			installed. Otherwise memory region will be allocated
> +			below 4G, if available.
>  			It will be ignored if crashkernel=X is specified.
>  	crashkernel=size[KMG],low
> -			[KNL, X86-64, ARM64] range under 4G. When crashkernel=X,high
> +			[KNL, X86-64, ARM64, RISCV] range under 4G. When crashkernel=X,high
>  			is passed, kernel could allocate physical memory region
>  			above 4G, that cause second kernel crash on system
>  			that require some amount of low memory, e.g. swiotlb
> @@ -874,6 +874,7 @@
>  			size is	platform dependent.
>  			  --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
>  			  --> arm64: 128MiB
> +			  --> riscv: 128MiB
>  			This one lets the user specify own low range under 4G
>  			for second kernel instead.
>  			0: to disable low allocation.
> 

-- 
Regards,
  Zhen Lei