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[PATCH -fixes 2/2] riscv: Do not set initial_boot_params to the linear address of the dtb

Alexandre Ghiti posted 2 patches 2 years, 10 months ago
There is a newer version of this series
[PATCH -fixes 2/2] riscv: Do not set initial_boot_params to the linear address of the dtb
Posted by Alexandre Ghiti 2 years, 10 months ago 
Now that the dtb early mapping was moved in the fixmap region, we can
keep using this address since it is present in swapper_pg_dir, so remove
the dtb relocation which was wrong anyway since early_memremap is
restricted to 256K whereas the maximum fdt size is 2MB.

Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
---
 arch/riscv/kernel/setup.c |  5 +----
 arch/riscv/mm/init.c      | 21 ++-------------------
 2 files changed, 3 insertions(+), 23 deletions(-)

diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 542eed85ad2c..a059b73f4ddb 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -278,10 +278,7 @@ void __init setup_arch(char **cmdline_p)
 #if IS_ENABLED(CONFIG_BUILTIN_DTB)
 	unflatten_and_copy_device_tree();
 #else
-	if (early_init_dt_verify(__va(XIP_FIXUP(dtb_early_pa))))
-		unflatten_device_tree();
-	else
-		pr_err("No DTB found in kernel mappings\n");
+	unflatten_device_tree();
 #endif
 	misc_mem_init();
 
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index fb78d6bbabae..0f14f4a8d179 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -249,25 +249,8 @@ static void __init setup_bootmem(void)
 	 * early_init_fdt_reserve_self() since __pa() does
 	 * not work for DTB pointers that are fixmap addresses
 	 */
-	if (!IS_ENABLED(CONFIG_BUILTIN_DTB)) {
-		/*
-		 * In case the DTB is not located in a memory region we won't
-		 * be able to locate it later on via the linear mapping and
-		 * get a segfault when accessing it via __va(dtb_early_pa).
-		 * To avoid this situation copy DTB to a memory region.
-		 * Note that memblock_phys_alloc will also reserve DTB region.
-		 */
-		if (!memblock_is_memory(dtb_early_pa)) {
-			size_t fdt_size = fdt_totalsize(dtb_early_va);
-			phys_addr_t new_dtb_early_pa = memblock_phys_alloc(fdt_size, PAGE_SIZE);
-			void *new_dtb_early_va = early_memremap(new_dtb_early_pa, fdt_size);
-
-			memcpy(new_dtb_early_va, dtb_early_va, fdt_size);
-			early_memunmap(new_dtb_early_va, fdt_size);
-			_dtb_early_pa = new_dtb_early_pa;
-		} else
-			memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
-	}
+	if (!IS_ENABLED(CONFIG_BUILTIN_DTB))
+		memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
 
 	dma_contiguous_reserve(dma32_phys_limit);
 	if (IS_ENABLED(CONFIG_64BIT))
-- 
2.37.2
Re: [PATCH -fixes 2/2] riscv: Do not set initial_boot_params to the linear address of the dtb
Posted by Conor Dooley 2 years, 10 months ago 
On Thu, Mar 23, 2023 at 05:33:47PM +0100, Alexandre Ghiti wrote:
> Now that the dtb early mapping was moved in the fixmap region, we can
> keep using this address since it is present in swapper_pg_dir, so remove
> the dtb relocation which was wrong anyway since early_memremap is
> restricted to 256K whereas the maximum fdt size is 2MB.

I feel bad making this comment since only one of us is a native speaker,
but for the future would you mind breaking up overly long sentences like
the above? Say:

	Now that the dtb early mapping was moved in the fixmap region, we can
	keep using this address since it is present in swapper_pg_dir, and
	remove the dtb relocation.
	The relocation was wrong anyway since early_memremap() is restricted to
	256K whereas the maximum fdt size is 2MB.

> 
> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> ---
>  arch/riscv/kernel/setup.c |  5 +----
>  arch/riscv/mm/init.c      | 21 ++-------------------
>  2 files changed, 3 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index 542eed85ad2c..a059b73f4ddb 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -278,10 +278,7 @@ void __init setup_arch(char **cmdline_p)
>  #if IS_ENABLED(CONFIG_BUILTIN_DTB)
>  	unflatten_and_copy_device_tree();
>  #else
> -	if (early_init_dt_verify(__va(XIP_FIXUP(dtb_early_pa))))

btw, how come it is safe now to drop this? This feels like a separate
change that should be its own commit, no?

Cheers,
Conor.

> -		unflatten_device_tree();
> -	else
> -		pr_err("No DTB found in kernel mappings\n");
> +	unflatten_device_tree();
>  #endif
>  	misc_mem_init();
>  
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index fb78d6bbabae..0f14f4a8d179 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -249,25 +249,8 @@ static void __init setup_bootmem(void)
>  	 * early_init_fdt_reserve_self() since __pa() does
>  	 * not work for DTB pointers that are fixmap addresses
>  	 */
> -	if (!IS_ENABLED(CONFIG_BUILTIN_DTB)) {
> -		/*
> -		 * In case the DTB is not located in a memory region we won't
> -		 * be able to locate it later on via the linear mapping and
> -		 * get a segfault when accessing it via __va(dtb_early_pa).
> -		 * To avoid this situation copy DTB to a memory region.
> -		 * Note that memblock_phys_alloc will also reserve DTB region.
> -		 */
> -		if (!memblock_is_memory(dtb_early_pa)) {
> -			size_t fdt_size = fdt_totalsize(dtb_early_va);
> -			phys_addr_t new_dtb_early_pa = memblock_phys_alloc(fdt_size, PAGE_SIZE);
> -			void *new_dtb_early_va = early_memremap(new_dtb_early_pa, fdt_size);
> -
> -			memcpy(new_dtb_early_va, dtb_early_va, fdt_size);
> -			early_memunmap(new_dtb_early_va, fdt_size);
> -			_dtb_early_pa = new_dtb_early_pa;
> -		} else
> -			memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
> -	}
> +	if (!IS_ENABLED(CONFIG_BUILTIN_DTB))
> +		memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
>  
>  	dma_contiguous_reserve(dma32_phys_limit);
>  	if (IS_ENABLED(CONFIG_64BIT))
> -- 
> 2.37.2
> 
>
Re: [PATCH -fixes 2/2] riscv: Do not set initial_boot_params to the linear address of the dtb
Posted by Alexandre Ghiti 2 years, 10 months ago 
On 3/27/23 13:16, Conor Dooley wrote:
> On Thu, Mar 23, 2023 at 05:33:47PM +0100, Alexandre Ghiti wrote:
>> Now that the dtb early mapping was moved in the fixmap region, we can
>> keep using this address since it is present in swapper_pg_dir, so remove
>> the dtb relocation which was wrong anyway since early_memremap is
>> restricted to 256K whereas the maximum fdt size is 2MB.
> I feel bad making this comment since only one of us is a native speaker,
> but for the future would you mind breaking up overly long sentences like
> the above? Say:
>
> 	Now that the dtb early mapping was moved in the fixmap region, we can
> 	keep using this address since it is present in swapper_pg_dir, and
> 	remove the dtb relocation.
> 	The relocation was wrong anyway since early_memremap() is restricted to
> 	256K whereas the maximum fdt size is 2MB.


Sure!


>> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
>> ---
>>   arch/riscv/kernel/setup.c |  5 +----
>>   arch/riscv/mm/init.c      | 21 ++-------------------
>>   2 files changed, 3 insertions(+), 23 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
>> index 542eed85ad2c..a059b73f4ddb 100644
>> --- a/arch/riscv/kernel/setup.c
>> +++ b/arch/riscv/kernel/setup.c
>> @@ -278,10 +278,7 @@ void __init setup_arch(char **cmdline_p)
>>   #if IS_ENABLED(CONFIG_BUILTIN_DTB)
>>   	unflatten_and_copy_device_tree();
>>   #else
>> -	if (early_init_dt_verify(__va(XIP_FIXUP(dtb_early_pa))))
> btw, how come it is safe now to drop this? This feels like a separate
> change that should be its own commit, no?


It is safe because early_init_dt_verify is already called in parse_dtb 
and since the dtb address does not change anymore, no need to reset 
initial_boot_params. So I'll split this one, thanks.


>
> Cheers,
> Conor.
>
>> -		unflatten_device_tree();
>> -	else
>> -		pr_err("No DTB found in kernel mappings\n");
>> +	unflatten_device_tree();
>>   #endif
>>   	misc_mem_init();
>>   
>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>> index fb78d6bbabae..0f14f4a8d179 100644
>> --- a/arch/riscv/mm/init.c
>> +++ b/arch/riscv/mm/init.c
>> @@ -249,25 +249,8 @@ static void __init setup_bootmem(void)
>>   	 * early_init_fdt_reserve_self() since __pa() does
>>   	 * not work for DTB pointers that are fixmap addresses
>>   	 */
>> -	if (!IS_ENABLED(CONFIG_BUILTIN_DTB)) {
>> -		/*
>> -		 * In case the DTB is not located in a memory region we won't
>> -		 * be able to locate it later on via the linear mapping and
>> -		 * get a segfault when accessing it via __va(dtb_early_pa).
>> -		 * To avoid this situation copy DTB to a memory region.
>> -		 * Note that memblock_phys_alloc will also reserve DTB region.
>> -		 */
>> -		if (!memblock_is_memory(dtb_early_pa)) {
>> -			size_t fdt_size = fdt_totalsize(dtb_early_va);
>> -			phys_addr_t new_dtb_early_pa = memblock_phys_alloc(fdt_size, PAGE_SIZE);
>> -			void *new_dtb_early_va = early_memremap(new_dtb_early_pa, fdt_size);
>> -
>> -			memcpy(new_dtb_early_va, dtb_early_va, fdt_size);
>> -			early_memunmap(new_dtb_early_va, fdt_size);
>> -			_dtb_early_pa = new_dtb_early_pa;
>> -		} else
>> -			memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
>> -	}
>> +	if (!IS_ENABLED(CONFIG_BUILTIN_DTB))
>> +		memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
>>   
>>   	dma_contiguous_reserve(dma32_phys_limit);
>>   	if (IS_ENABLED(CONFIG_64BIT))
>> -- 
>> 2.37.2
>>
>>
>>
>> _______________________________________________
>> linux-riscv mailing list
>> linux-riscv@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-riscv
Re: [PATCH -fixes 2/2] riscv: Do not set initial_boot_params to the linear address of the dtb
Posted by Conor Dooley 2 years, 10 months ago 
On Wed, Mar 29, 2023 at 10:09:13AM +0200, Alexandre Ghiti wrote:
> On 3/27/23 13:16, Conor Dooley wrote:
> > On Thu, Mar 23, 2023 at 05:33:47PM +0100, Alexandre Ghiti wrote:
> > > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> > > index 542eed85ad2c..a059b73f4ddb 100644
> > > --- a/arch/riscv/kernel/setup.c
> > > +++ b/arch/riscv/kernel/setup.c
> > > @@ -278,10 +278,7 @@ void __init setup_arch(char **cmdline_p)
> > >   #if IS_ENABLED(CONFIG_BUILTIN_DTB)
> > >   	unflatten_and_copy_device_tree();
> > >   #else
> > > -	if (early_init_dt_verify(__va(XIP_FIXUP(dtb_early_pa))))
> 
> > btw, how come it is safe now to drop this? This feels like a separate
> > change that should be its own commit, no?
> 
> 
> It is safe because early_init_dt_verify is already called in parse_dtb and

Yah, that's what I figured. Cool.

> since the dtb address does not change anymore, no need to reset
> initial_boot_params. So I'll split this one, thanks.

Worth noting the point at which this became redundant in your commit
message when you do.

Thanks,
Conor.

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