[PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Kefeng Wang]

The kernel could be benifit due to BLOCK_MAPPINGS, see commit
031495635b46 ("arm64: Do not defer reserve_crashkernel() for
platforms with no DMA memory zones"), if there is only with
ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
earlier in arm64_memblock_init(), then we will benifit too.

Cc: Vijay Balakrishna <vijayb@linux.microsoft.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 arch/arm64/mm/init.c | 18 ++++++++++--------
 arch/arm64/mm/mmu.c  |  6 ++----
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 8ac25f19084e..9dded8779d72 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -157,14 +157,14 @@ static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
 	return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
 }
 
+phys_addr_t __ro_after_init dma32_phys_limit;
 static void __init zone_sizes_init(unsigned long min, unsigned long max)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
-	unsigned int __maybe_unused acpi_zone_dma_bits;
-	unsigned int __maybe_unused dt_zone_dma_bits;
-	phys_addr_t __maybe_unused dma32_phys_limit = max_zone_phys(32);
-
 #ifdef CONFIG_ZONE_DMA
+	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);
@@ -173,8 +173,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
 #endif
 #ifdef CONFIG_ZONE_DMA32
 	max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
-	if (!arm64_dma_phys_limit)
-		arm64_dma_phys_limit = dma32_phys_limit;
 #endif
 	max_zone_pfns[ZONE_NORMAL] = max;
 
@@ -336,8 +334,12 @@ void __init arm64_memblock_init(void)
 
 	early_init_fdt_scan_reserved_mem();
 
-	if (!IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32))
+	dma32_phys_limit = max_zone_phys(32);
+	if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
+		if (IS_ENABLED(CONFIG_ZONE_DMA32))
+			arm64_dma_phys_limit = dma32_phys_limit;
 		reserve_crashkernel();
+	}
 
 	high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
 }
@@ -385,7 +387,7 @@ 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) || IS_ENABLED(CONFIG_ZONE_DMA32))
+	if (IS_ENABLED(CONFIG_ZONE_DMA))
 		reserve_crashkernel();
 
 	memblock_dump_all();
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 626ec32873c6..23734481318a 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -529,8 +529,7 @@ static void __init map_mem(pgd_t *pgdp)
 
 #ifdef CONFIG_KEXEC_CORE
 	if (crash_mem_map) {
-		if (IS_ENABLED(CONFIG_ZONE_DMA) ||
-		    IS_ENABLED(CONFIG_ZONE_DMA32))
+		if (IS_ENABLED(CONFIG_ZONE_DMA))
 			flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 		else if (crashk_res.end)
 			memblock_mark_nomap(crashk_res.start,
@@ -571,8 +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) && !IS_ENABLED(CONFIG_ZONE_DMA32)) {
+	if (crash_mem_map && !IS_ENABLED(CONFIG_ZONE_DMA)) {
 		if (crashk_res.end) {
 			__map_memblock(pgdp, crashk_res.start,
 				       crashk_res.end + 1,
-- 
2.26.2

[PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Kefeng Wang]

The kernel could be benifit due to BLOCK_MAPPINGS, see commit
031495635b46 ("arm64: Do not defer reserve_crashkernel() for
platforms with no DMA memory zones"), if there is only with
ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
earlier in arm64_memblock_init(), then we will benifit too.

Cc: Vijay Balakrishna <vijayb@linux.microsoft.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 arch/arm64/mm/init.c | 18 ++++++++++--------
 arch/arm64/mm/mmu.c  |  6 ++----
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 8ac25f19084e..9dded8779d72 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -157,14 +157,14 @@ static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
 	return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
 }
 
+phys_addr_t __ro_after_init dma32_phys_limit;
 static void __init zone_sizes_init(unsigned long min, unsigned long max)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
-	unsigned int __maybe_unused acpi_zone_dma_bits;
-	unsigned int __maybe_unused dt_zone_dma_bits;
-	phys_addr_t __maybe_unused dma32_phys_limit = max_zone_phys(32);
-
 #ifdef CONFIG_ZONE_DMA
+	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);
@@ -173,8 +173,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
 #endif
 #ifdef CONFIG_ZONE_DMA32
 	max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
-	if (!arm64_dma_phys_limit)
-		arm64_dma_phys_limit = dma32_phys_limit;
 #endif
 	max_zone_pfns[ZONE_NORMAL] = max;
 
@@ -336,8 +334,12 @@ void __init arm64_memblock_init(void)
 
 	early_init_fdt_scan_reserved_mem();
 
-	if (!IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32))
+	dma32_phys_limit = max_zone_phys(32);
+	if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
+		if (IS_ENABLED(CONFIG_ZONE_DMA32))
+			arm64_dma_phys_limit = dma32_phys_limit;
 		reserve_crashkernel();
+	}
 
 	high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
 }
@@ -385,7 +387,7 @@ 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) || IS_ENABLED(CONFIG_ZONE_DMA32))
+	if (IS_ENABLED(CONFIG_ZONE_DMA))
 		reserve_crashkernel();
 
 	memblock_dump_all();
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 626ec32873c6..23734481318a 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -529,8 +529,7 @@ static void __init map_mem(pgd_t *pgdp)
 
 #ifdef CONFIG_KEXEC_CORE
 	if (crash_mem_map) {
-		if (IS_ENABLED(CONFIG_ZONE_DMA) ||
-		    IS_ENABLED(CONFIG_ZONE_DMA32))
+		if (IS_ENABLED(CONFIG_ZONE_DMA))
 			flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 		else if (crashk_res.end)
 			memblock_mark_nomap(crashk_res.start,
@@ -571,8 +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) && !IS_ENABLED(CONFIG_ZONE_DMA32)) {
+	if (crash_mem_map && !IS_ENABLED(CONFIG_ZONE_DMA)) {
 		if (crashk_res.end) {
 			__map_memblock(pgdp, crashk_res.start,
 				       crashk_res.end + 1,
-- 
2.26.2


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linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH 2/2] arm64: mm: Cleanup useless parameters in zone_sizes_init()

[Kefeng Wang]

Directly use max_pfn for max and no one use min, kill them.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 arch/arm64/mm/init.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 9dded8779d72..eacb38c2d225 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -158,7 +158,7 @@ static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
 }
 
 phys_addr_t __ro_after_init dma32_phys_limit;
-static void __init zone_sizes_init(unsigned long min, unsigned long max)
+static void __init zone_sizes_init(void)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
 #ifdef CONFIG_ZONE_DMA
@@ -174,7 +174,7 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
 #ifdef CONFIG_ZONE_DMA32
 	max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
 #endif
-	max_zone_pfns[ZONE_NORMAL] = max;
+	max_zone_pfns[ZONE_NORMAL] = max_pfn;
 
 	free_area_init(max_zone_pfns);
 }
@@ -376,7 +376,7 @@ void __init bootmem_init(void)
 	 * done after the fixed reservations
 	 */
 	sparse_init();
-	zone_sizes_init(min, max);
+	zone_sizes_init();
 
 	/*
 	 * Reserve the CMA area after arm64_dma_phys_limit was initialised.
-- 
2.26.2

[PATCH 2/2] arm64: mm: Cleanup useless parameters in zone_sizes_init()

[Kefeng Wang]

Directly use max_pfn for max and no one use min, kill them.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 arch/arm64/mm/init.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 9dded8779d72..eacb38c2d225 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -158,7 +158,7 @@ static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
 }
 
 phys_addr_t __ro_after_init dma32_phys_limit;
-static void __init zone_sizes_init(unsigned long min, unsigned long max)
+static void __init zone_sizes_init(void)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
 #ifdef CONFIG_ZONE_DMA
@@ -174,7 +174,7 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
 #ifdef CONFIG_ZONE_DMA32
 	max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
 #endif
-	max_zone_pfns[ZONE_NORMAL] = max;
+	max_zone_pfns[ZONE_NORMAL] = max_pfn;
 
 	free_area_init(max_zone_pfns);
 }
@@ -376,7 +376,7 @@ void __init bootmem_init(void)
 	 * done after the fixed reservations
 	 */
 	sparse_init();
-	zone_sizes_init(min, max);
+	zone_sizes_init();
 
 	/*
 	 * Reserve the CMA area after arm64_dma_phys_limit was initialised.
-- 
2.26.2


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linux-arm-kernel mailing list
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Re: [PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Vijay Balakrishna]

On 3/24/2022 10:53 PM, Kefeng Wang wrote:
> The kernel could be benifit due to BLOCK_MAPPINGS, see commit
> 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
> platforms with no DMA memory zones"), if there is only with
> ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
> earlier in arm64_memblock_init(), then we will benifit too.

Thanks for noticing platforms with just ZONE_DMA32 config can also 
benefit BLOCK_MAPPINGS.  I assume you have access to one where you 
notice the difference with proposed changes and able to test.  I did 
test proposed changes on SoC we use with IOMMU (no ZONE_DMA configs 
enabled).

Nits --
- benifit -> benefit
- consider making commit message clear, "then we will.." seems you are 
referring to platforms with just ZONE_DMA32 config enabled
- to reflect new change consider updating comment added in commit 
031495635b46

> 
> Cc: Vijay Balakrishna <vijayb@linux.microsoft.com>
> Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
> Cc: Will Deacon <will@kernel.org>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>

Reviewed-by: Vijay Balakrishna <vijayb@linux.microsoft.com>

> ---
>   arch/arm64/mm/init.c | 18 ++++++++++--------
>   arch/arm64/mm/mmu.c  |  6 ++----
>   2 files changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 8ac25f19084e..9dded8779d72 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -157,14 +157,14 @@ static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
>   	return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
>   }
>   
> +phys_addr_t __ro_after_init dma32_phys_limit;
>   static void __init zone_sizes_init(unsigned long min, unsigned long max)
>   {
>   	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
> -	unsigned int __maybe_unused acpi_zone_dma_bits;
> -	unsigned int __maybe_unused dt_zone_dma_bits;
> -	phys_addr_t __maybe_unused dma32_phys_limit = max_zone_phys(32);
> -
>   #ifdef CONFIG_ZONE_DMA
> +	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);
> @@ -173,8 +173,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
>   #endif
>   #ifdef CONFIG_ZONE_DMA32
>   	max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
> -	if (!arm64_dma_phys_limit)
> -		arm64_dma_phys_limit = dma32_phys_limit;
>   #endif
>   	max_zone_pfns[ZONE_NORMAL] = max;
>   
> @@ -336,8 +334,12 @@ void __init arm64_memblock_init(void)
>   
>   	early_init_fdt_scan_reserved_mem();
>   
> -	if (!IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32))
> +	dma32_phys_limit = max_zone_phys(32);
> +	if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
> +		if (IS_ENABLED(CONFIG_ZONE_DMA32))
> +			arm64_dma_phys_limit = dma32_phys_limit;
>   		reserve_crashkernel();
> +	}
>   
>   	high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
>   }
> @@ -385,7 +387,7 @@ 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) || IS_ENABLED(CONFIG_ZONE_DMA32))
> +	if (IS_ENABLED(CONFIG_ZONE_DMA))
>   		reserve_crashkernel();
>   
>   	memblock_dump_all();
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 626ec32873c6..23734481318a 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -529,8 +529,7 @@ static void __init map_mem(pgd_t *pgdp)
>   
>   #ifdef CONFIG_KEXEC_CORE
>   	if (crash_mem_map) {
> -		if (IS_ENABLED(CONFIG_ZONE_DMA) ||
> -		    IS_ENABLED(CONFIG_ZONE_DMA32))
> +		if (IS_ENABLED(CONFIG_ZONE_DMA))
>   			flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>   		else if (crashk_res.end)
>   			memblock_mark_nomap(crashk_res.start,
> @@ -571,8 +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) && !IS_ENABLED(CONFIG_ZONE_DMA32)) {
> +	if (crash_mem_map && !IS_ENABLED(CONFIG_ZONE_DMA)) {
>   		if (crashk_res.end) {
>   			__map_memblock(pgdp, crashk_res.start,
>   				       crashk_res.end + 1,

Re: [PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Vijay Balakrishna]

On 3/24/2022 10:53 PM, Kefeng Wang wrote:
> The kernel could be benifit due to BLOCK_MAPPINGS, see commit
> 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
> platforms with no DMA memory zones"), if there is only with
> ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
> earlier in arm64_memblock_init(), then we will benifit too.

Thanks for noticing platforms with just ZONE_DMA32 config can also 
benefit BLOCK_MAPPINGS.  I assume you have access to one where you 
notice the difference with proposed changes and able to test.  I did 
test proposed changes on SoC we use with IOMMU (no ZONE_DMA configs 
enabled).

Nits --
- benifit -> benefit
- consider making commit message clear, "then we will.." seems you are 
referring to platforms with just ZONE_DMA32 config enabled
- to reflect new change consider updating comment added in commit 
031495635b46

> 
> Cc: Vijay Balakrishna <vijayb@linux.microsoft.com>
> Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
> Cc: Will Deacon <will@kernel.org>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>

Reviewed-by: Vijay Balakrishna <vijayb@linux.microsoft.com>

> ---
>   arch/arm64/mm/init.c | 18 ++++++++++--------
>   arch/arm64/mm/mmu.c  |  6 ++----
>   2 files changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 8ac25f19084e..9dded8779d72 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -157,14 +157,14 @@ static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
>   	return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
>   }
>   
> +phys_addr_t __ro_after_init dma32_phys_limit;
>   static void __init zone_sizes_init(unsigned long min, unsigned long max)
>   {
>   	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
> -	unsigned int __maybe_unused acpi_zone_dma_bits;
> -	unsigned int __maybe_unused dt_zone_dma_bits;
> -	phys_addr_t __maybe_unused dma32_phys_limit = max_zone_phys(32);
> -
>   #ifdef CONFIG_ZONE_DMA
> +	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);
> @@ -173,8 +173,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
>   #endif
>   #ifdef CONFIG_ZONE_DMA32
>   	max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
> -	if (!arm64_dma_phys_limit)
> -		arm64_dma_phys_limit = dma32_phys_limit;
>   #endif
>   	max_zone_pfns[ZONE_NORMAL] = max;
>   
> @@ -336,8 +334,12 @@ void __init arm64_memblock_init(void)
>   
>   	early_init_fdt_scan_reserved_mem();
>   
> -	if (!IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32))
> +	dma32_phys_limit = max_zone_phys(32);
> +	if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
> +		if (IS_ENABLED(CONFIG_ZONE_DMA32))
> +			arm64_dma_phys_limit = dma32_phys_limit;
>   		reserve_crashkernel();
> +	}
>   
>   	high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
>   }
> @@ -385,7 +387,7 @@ 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) || IS_ENABLED(CONFIG_ZONE_DMA32))
> +	if (IS_ENABLED(CONFIG_ZONE_DMA))
>   		reserve_crashkernel();
>   
>   	memblock_dump_all();
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 626ec32873c6..23734481318a 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -529,8 +529,7 @@ static void __init map_mem(pgd_t *pgdp)
>   
>   #ifdef CONFIG_KEXEC_CORE
>   	if (crash_mem_map) {
> -		if (IS_ENABLED(CONFIG_ZONE_DMA) ||
> -		    IS_ENABLED(CONFIG_ZONE_DMA32))
> +		if (IS_ENABLED(CONFIG_ZONE_DMA))
>   			flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>   		else if (crashk_res.end)
>   			memblock_mark_nomap(crashk_res.start,
> @@ -571,8 +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) && !IS_ENABLED(CONFIG_ZONE_DMA32)) {
> +	if (crash_mem_map && !IS_ENABLED(CONFIG_ZONE_DMA)) {
>   		if (crashk_res.end) {
>   			__map_memblock(pgdp, crashk_res.start,
>   				       crashk_res.end + 1,

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Re: [PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Florian Fainelli]

On 3/24/2022 10:53 PM, Kefeng Wang wrote:
> The kernel could be benifit due to BLOCK_MAPPINGS, see commit
> 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
> platforms with no DMA memory zones"), if there is only with
> ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
> earlier in arm64_memblock_init(), then we will benifit too.
> 
> Cc: Vijay Balakrishna <vijayb@linux.microsoft.com>
> Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
> Cc: Will Deacon <will@kernel.org>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>   arch/arm64/mm/init.c | 18 ++++++++++--------
>   arch/arm64/mm/mmu.c  |  6 ++----
>   2 files changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 8ac25f19084e..9dded8779d72 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -157,14 +157,14 @@ static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
>   	return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
>   }
>   
> +phys_addr_t __ro_after_init dma32_phys_limit;

This variable should still be scoped to this file, it is not used 
outside of arch/arm64/mm/init.c.
-- 
Florian

Re: [PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Florian Fainelli]

On 3/24/2022 10:53 PM, Kefeng Wang wrote:
> The kernel could be benifit due to BLOCK_MAPPINGS, see commit
> 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
> platforms with no DMA memory zones"), if there is only with
> ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
> earlier in arm64_memblock_init(), then we will benifit too.
> 
> Cc: Vijay Balakrishna <vijayb@linux.microsoft.com>
> Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
> Cc: Will Deacon <will@kernel.org>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>   arch/arm64/mm/init.c | 18 ++++++++++--------
>   arch/arm64/mm/mmu.c  |  6 ++----
>   2 files changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 8ac25f19084e..9dded8779d72 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -157,14 +157,14 @@ static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
>   	return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
>   }
>   
> +phys_addr_t __ro_after_init dma32_phys_limit;

This variable should still be scoped to this file, it is not used 
outside of arch/arm64/mm/init.c.
-- 
Florian

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Re: [PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Kefeng Wang]

On 2022/3/30 6:29, Vijay Balakrishna wrote:
>
>
> On 3/24/2022 10:53 PM, Kefeng Wang wrote:
>> The kernel could be benifit due to BLOCK_MAPPINGS, see commit
>> 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
>> platforms with no DMA memory zones"), if there is only with
>> ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
>> earlier in arm64_memblock_init(), then we will benifit too.
>
> Thanks for noticing platforms with just ZONE_DMA32 config can also 
> benefit BLOCK_MAPPINGS.  I assume you have access to one where you 
> notice the difference with proposed changes and able to test.  I did 
> test proposed changes on SoC we use with IOMMU (no ZONE_DMA configs 
> enabled).
I backported your patches into 5.10 and tested(unixbench will benifit 
due to block mapping, only with DMA32 and rodata=false)
>
> Nits --
> - benifit -> benefit
> - consider making commit message clear, "then we will.." seems you are 
> referring to platforms with just ZONE_DMA32 config enabled
> - to reflect new change consider updating comment added in commit 
> 031495635b46
Thanks for your reviewing,  will update and test with upstream.
>
>>
>> Cc: Vijay Balakrishna <vijayb@linux.microsoft.com>
>> Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
>> Cc: Will Deacon <will@kernel.org>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>
> Reviewed-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
>
>> ---
>>   arch/arm64/mm/init.c | 18 ++++++++++--------
>>   arch/arm64/mm/mmu.c  |  6 ++----
>>   2 files changed, 12 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>> index 8ac25f19084e..9dded8779d72 100644
>> --- a/arch/arm64/mm/init.c
>> +++ b/arch/arm64/mm/init.c
>> @@ -157,14 +157,14 @@ static phys_addr_t __init 
>> max_zone_phys(unsigned int zone_bits)
>>       return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
>>   }
>>   +phys_addr_t __ro_after_init dma32_phys_limit;
Will make it static, suggested by Florian
>>   static void __init zone_sizes_init(unsigned long min, unsigned long 
>> max)
>>   {
>>       unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
>> -    unsigned int __maybe_unused acpi_zone_dma_bits;
>> -    unsigned int __maybe_unused dt_zone_dma_bits;
>> -    phys_addr_t __maybe_unused dma32_phys_limit = max_zone_phys(32);
>> -
>>   #ifdef CONFIG_ZONE_DMA
>> +    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);
>> @@ -173,8 +173,6 @@ static void __init zone_sizes_init(unsigned long 
>> min, unsigned long max)
>>   #endif
>>   #ifdef CONFIG_ZONE_DMA32
>>       max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
>> -    if (!arm64_dma_phys_limit)
>> -        arm64_dma_phys_limit = dma32_phys_limit;
>>   #endif
>>       max_zone_pfns[ZONE_NORMAL] = max;
>>   @@ -336,8 +334,12 @@ void __init arm64_memblock_init(void)
>>         early_init_fdt_scan_reserved_mem();
>>   -    if (!IS_ENABLED(CONFIG_ZONE_DMA) && 
>> !IS_ENABLED(CONFIG_ZONE_DMA32))
>> +    dma32_phys_limit = max_zone_phys(32);
>> +    if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
>> +        if (IS_ENABLED(CONFIG_ZONE_DMA32))
>> +            arm64_dma_phys_limit = dma32_phys_limit;
>>           reserve_crashkernel();
>> +    }
>>         high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
>>   }
>> @@ -385,7 +387,7 @@ 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) || IS_ENABLED(CONFIG_ZONE_DMA32))
>> +    if (IS_ENABLED(CONFIG_ZONE_DMA))
>>           reserve_crashkernel();
>>         memblock_dump_all();
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index 626ec32873c6..23734481318a 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -529,8 +529,7 @@ static void __init map_mem(pgd_t *pgdp)
>>     #ifdef CONFIG_KEXEC_CORE
>>       if (crash_mem_map) {
>> -        if (IS_ENABLED(CONFIG_ZONE_DMA) ||
>> -            IS_ENABLED(CONFIG_ZONE_DMA32))
>> +        if (IS_ENABLED(CONFIG_ZONE_DMA))
>>               flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>>           else if (crashk_res.end)
>>               memblock_mark_nomap(crashk_res.start,
>> @@ -571,8 +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) && 
>> !IS_ENABLED(CONFIG_ZONE_DMA32)) {
>> +    if (crash_mem_map && !IS_ENABLED(CONFIG_ZONE_DMA)) {
>>           if (crashk_res.end) {
>>               __map_memblock(pgdp, crashk_res.start,
>>                          crashk_res.end + 1,
> .

Re: [PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Kefeng Wang]

On 2022/3/30 6:29, Vijay Balakrishna wrote:
>
>
> On 3/24/2022 10:53 PM, Kefeng Wang wrote:
>> The kernel could be benifit due to BLOCK_MAPPINGS, see commit
>> 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
>> platforms with no DMA memory zones"), if there is only with
>> ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
>> earlier in arm64_memblock_init(), then we will benifit too.
>
> Thanks for noticing platforms with just ZONE_DMA32 config can also 
> benefit BLOCK_MAPPINGS.  I assume you have access to one where you 
> notice the difference with proposed changes and able to test.  I did 
> test proposed changes on SoC we use with IOMMU (no ZONE_DMA configs 
> enabled).
I backported your patches into 5.10 and tested(unixbench will benifit 
due to block mapping, only with DMA32 and rodata=false)
>
> Nits --
> - benifit -> benefit
> - consider making commit message clear, "then we will.." seems you are 
> referring to platforms with just ZONE_DMA32 config enabled
> - to reflect new change consider updating comment added in commit 
> 031495635b46
Thanks for your reviewing,  will update and test with upstream.
>
>>
>> Cc: Vijay Balakrishna <vijayb@linux.microsoft.com>
>> Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
>> Cc: Will Deacon <will@kernel.org>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>
> Reviewed-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
>
>> ---
>>   arch/arm64/mm/init.c | 18 ++++++++++--------
>>   arch/arm64/mm/mmu.c  |  6 ++----
>>   2 files changed, 12 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>> index 8ac25f19084e..9dded8779d72 100644
>> --- a/arch/arm64/mm/init.c
>> +++ b/arch/arm64/mm/init.c
>> @@ -157,14 +157,14 @@ static phys_addr_t __init 
>> max_zone_phys(unsigned int zone_bits)
>>       return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
>>   }
>>   +phys_addr_t __ro_after_init dma32_phys_limit;
Will make it static, suggested by Florian
>>   static void __init zone_sizes_init(unsigned long min, unsigned long 
>> max)
>>   {
>>       unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
>> -    unsigned int __maybe_unused acpi_zone_dma_bits;
>> -    unsigned int __maybe_unused dt_zone_dma_bits;
>> -    phys_addr_t __maybe_unused dma32_phys_limit = max_zone_phys(32);
>> -
>>   #ifdef CONFIG_ZONE_DMA
>> +    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);
>> @@ -173,8 +173,6 @@ static void __init zone_sizes_init(unsigned long 
>> min, unsigned long max)
>>   #endif
>>   #ifdef CONFIG_ZONE_DMA32
>>       max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
>> -    if (!arm64_dma_phys_limit)
>> -        arm64_dma_phys_limit = dma32_phys_limit;
>>   #endif
>>       max_zone_pfns[ZONE_NORMAL] = max;
>>   @@ -336,8 +334,12 @@ void __init arm64_memblock_init(void)
>>         early_init_fdt_scan_reserved_mem();
>>   -    if (!IS_ENABLED(CONFIG_ZONE_DMA) && 
>> !IS_ENABLED(CONFIG_ZONE_DMA32))
>> +    dma32_phys_limit = max_zone_phys(32);
>> +    if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
>> +        if (IS_ENABLED(CONFIG_ZONE_DMA32))
>> +            arm64_dma_phys_limit = dma32_phys_limit;
>>           reserve_crashkernel();
>> +    }
>>         high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
>>   }
>> @@ -385,7 +387,7 @@ 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) || IS_ENABLED(CONFIG_ZONE_DMA32))
>> +    if (IS_ENABLED(CONFIG_ZONE_DMA))
>>           reserve_crashkernel();
>>         memblock_dump_all();
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index 626ec32873c6..23734481318a 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -529,8 +529,7 @@ static void __init map_mem(pgd_t *pgdp)
>>     #ifdef CONFIG_KEXEC_CORE
>>       if (crash_mem_map) {
>> -        if (IS_ENABLED(CONFIG_ZONE_DMA) ||
>> -            IS_ENABLED(CONFIG_ZONE_DMA32))
>> +        if (IS_ENABLED(CONFIG_ZONE_DMA))
>>               flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>>           else if (crashk_res.end)
>>               memblock_mark_nomap(crashk_res.start,
>> @@ -571,8 +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) && 
>> !IS_ENABLED(CONFIG_ZONE_DMA32)) {
>> +    if (crash_mem_map && !IS_ENABLED(CONFIG_ZONE_DMA)) {
>>           if (crashk_res.end) {
>>               __map_memblock(pgdp, crashk_res.start,
>>                          crashk_res.end + 1,
> .

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Re: [PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Kefeng Wang]

On 2022/3/30 6:29, Vijay Balakrishna wrote:
>
>
> On 3/24/2022 10:53 PM, Kefeng Wang wrote:
>> The kernel could be benifit due to BLOCK_MAPPINGS, see commit
>> 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
>> platforms with no DMA memory zones"), if there is only with
>> ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
>> earlier in arm64_memblock_init(), then we will benifit too.
>
> Thanks for noticing platforms with just ZONE_DMA32 config can also 
> benefit BLOCK_MAPPINGS.  I assume you have access to one where you 
> notice the difference with proposed changes and able to test.  I did 
> test proposed changes on SoC we use with IOMMU (no ZONE_DMA configs 
> enabled).
>
> Nits --
> - benifit -> benefit
> - consider making commit message clear, "then we will.." seems you are 
> referring to platforms with just ZONE_DMA32 config enabled
> - to reflect new change consider updating comment added in commit 
> 031495635b46
>
One more question, could we add new cmdline(eg, dma_force_32bit) to let 
the arm64 using

32bit dma  by default?  I think most platforms are not with small DMA 
bit(only found 20bit in Raspberry Pi 4?),

Here is a draft(based on this patch) to do it, if the kernel boot with 
this cmdline and even ZONE_DMA

is enabled, the kernel allows linear creation of block mapping, not sure 
this is the right way, any suggestion? Thanks.

diff --git a/arch/arm64/include/asm/processor.h 
b/arch/arm64/include/asm/processor.h
index 73e38d9a540c..8febed26aeed 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -100,6 +100,7 @@
                                         base)
  #endif /* CONFIG_ARM64_FORCE_52BIT */

+extern bool arm64_dma_force_32bit;
  extern phys_addr_t arm64_dma_phys_limit;
  #define ARCH_LOW_ADDRESS_LIMIT (arm64_dma_phys_limit - 1)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index d6f64819ef89..86aab5db735b 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -92,6 +92,16 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit;
  phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1;
  #endif

+bool __ro_after_init arm64_dma_force_32bit;
+static int __init arm64_dma_force_32bit_setup(char *p)
+{
+       arm64_dma_force_32bit = true;
+       zone_dma_bits = 32;
+
+       return 0;
+}
+early_param("dma_force_32bit", arm64_dma_force_32bit_setup);
+
  /*
   * reserve_crashkernel() - reserves memory for crash kernel
   *
@@ -165,10 +175,11 @@ static void __init zone_sizes_init(void)
  #ifdef CONFIG_ZONE_DMA
         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);
+       if (!arm64_dma_force_32bit) {
+               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
@@ -336,7 +347,7 @@ void __init arm64_memblock_init(void)
         early_init_fdt_scan_reserved_mem();

         dma32_phys_limit = max_zone_phys(32);
-       if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
+       if (!IS_ENABLED(CONFIG_ZONE_DMA) || arm64_dma_force_32bit) {
                 if (IS_ENABLED(CONFIG_ZONE_DMA32))
                         arm64_dma_phys_limit = dma32_phys_limit;
                 reserve_crashkernel();
@@ -388,7 +399,7 @@ 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 (IS_ENABLED(CONFIG_ZONE_DMA) && !arm64_dma_force_32bit)
                 reserve_crashkernel();

         memblock_dump_all();
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 23734481318a..9431ad581927 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 (IS_ENABLED(CONFIG_ZONE_DMA) && !arm64_dma_force_32bit)
                         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 && (!IS_ENABLED(CONFIG_ZONE_DMA) || 
arm64_dma_force_32bit)) {
                 if (crashk_res.end) {
                         __map_memblock(pgdp, crashk_res.start,
                                        crashk_res.end + 1,

Re: [PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Kefeng Wang]

On 2022/3/30 6:29, Vijay Balakrishna wrote:
>
>
> On 3/24/2022 10:53 PM, Kefeng Wang wrote:
>> The kernel could be benifit due to BLOCK_MAPPINGS, see commit
>> 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
>> platforms with no DMA memory zones"), if there is only with
>> ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
>> earlier in arm64_memblock_init(), then we will benifit too.
>
> Thanks for noticing platforms with just ZONE_DMA32 config can also 
> benefit BLOCK_MAPPINGS.  I assume you have access to one where you 
> notice the difference with proposed changes and able to test.  I did 
> test proposed changes on SoC we use with IOMMU (no ZONE_DMA configs 
> enabled).
>
> Nits --
> - benifit -> benefit
> - consider making commit message clear, "then we will.." seems you are 
> referring to platforms with just ZONE_DMA32 config enabled
> - to reflect new change consider updating comment added in commit 
> 031495635b46
>
One more question, could we add new cmdline(eg, dma_force_32bit) to let 
the arm64 using

32bit dma  by default?  I think most platforms are not with small DMA 
bit(only found 20bit in Raspberry Pi 4?),

Here is a draft(based on this patch) to do it, if the kernel boot with 
this cmdline and even ZONE_DMA

is enabled, the kernel allows linear creation of block mapping, not sure 
this is the right way, any suggestion? Thanks.

diff --git a/arch/arm64/include/asm/processor.h 
b/arch/arm64/include/asm/processor.h
index 73e38d9a540c..8febed26aeed 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -100,6 +100,7 @@
                                         base)
  #endif /* CONFIG_ARM64_FORCE_52BIT */

+extern bool arm64_dma_force_32bit;
  extern phys_addr_t arm64_dma_phys_limit;
  #define ARCH_LOW_ADDRESS_LIMIT (arm64_dma_phys_limit - 1)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index d6f64819ef89..86aab5db735b 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -92,6 +92,16 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit;
  phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1;
  #endif

+bool __ro_after_init arm64_dma_force_32bit;
+static int __init arm64_dma_force_32bit_setup(char *p)
+{
+       arm64_dma_force_32bit = true;
+       zone_dma_bits = 32;
+
+       return 0;
+}
+early_param("dma_force_32bit", arm64_dma_force_32bit_setup);
+
  /*
   * reserve_crashkernel() - reserves memory for crash kernel
   *
@@ -165,10 +175,11 @@ static void __init zone_sizes_init(void)
  #ifdef CONFIG_ZONE_DMA
         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);
+       if (!arm64_dma_force_32bit) {
+               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
@@ -336,7 +347,7 @@ void __init arm64_memblock_init(void)
         early_init_fdt_scan_reserved_mem();

         dma32_phys_limit = max_zone_phys(32);
-       if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
+       if (!IS_ENABLED(CONFIG_ZONE_DMA) || arm64_dma_force_32bit) {
                 if (IS_ENABLED(CONFIG_ZONE_DMA32))
                         arm64_dma_phys_limit = dma32_phys_limit;
                 reserve_crashkernel();
@@ -388,7 +399,7 @@ 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 (IS_ENABLED(CONFIG_ZONE_DMA) && !arm64_dma_force_32bit)
                 reserve_crashkernel();

         memblock_dump_all();
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 23734481318a..9431ad581927 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 (IS_ENABLED(CONFIG_ZONE_DMA) && !arm64_dma_force_32bit)
                         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 && (!IS_ENABLED(CONFIG_ZONE_DMA) || 
arm64_dma_force_32bit)) {
                 if (crashk_res.end) {
                         __map_memblock(pgdp, crashk_res.start,
                                        crashk_res.end + 1,



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