* [PATCH V2] riscv: Add BUG_ON() for no cpu nodes in devicetree
@ 2023-06-30 10:59 Song Shuai
2023-06-30 18:39 ` Conor Dooley
0 siblings, 1 reply; 3+ messages in thread
From: Song Shuai @ 2023-06-30 10:59 UTC (permalink / raw)
To: paul.walmsley, palmer, aou, conor.dooley, ajones, sunilvl,
heiko.stuebner, apatel, suagrfillet, evan, greentime.hu,
leyfoon.tan
Cc: linux-riscv, linux-kernel
When only the ACPI tables are passed to kernel, the tiny devictree created
by EFI Stub doesn't provide cpu nodes.
While if append the "acpi=off" to kernel cmdline to disable ACPI for kernel
the BUG_ON() in of_parse_and_init_cpus() indicates there's no boot cpu
found in the devicetree, not there're no cpu nodes in the devicetree.
Add BUG_ON() in the first place of of_parse_and_init_cpus() to make it clear.
Signed-off-by: Song Shuai <suagrfillet@gmail.com>
---
Changes since V1:
https://lore.kernel.org/linux-riscv/20230629105839.1160895-1-suagrfillet@gmail.com/
- revise the commit-msg and move the BUG_ON into of_parse_and_init_cpus() as Conor suggests
---
arch/riscv/kernel/smpboot.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 6ca2b5309aab..04d33afbdf55 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -147,6 +147,8 @@ static void __init of_parse_and_init_cpus(void)
int cpuid = 1;
int rc;
+ BUG_ON(!of_get_next_cpu_node(NULL));
+
cpu_set_ops(0);
for_each_of_cpu_node(dn) {
--
2.20.1
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^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH V2] riscv: Add BUG_ON() for no cpu nodes in devicetree
2023-06-30 10:59 [PATCH V2] riscv: Add BUG_ON() for no cpu nodes in devicetree Song Shuai
@ 2023-06-30 18:39 ` Conor Dooley
2023-07-11 22:58 ` Palmer Dabbelt
0 siblings, 1 reply; 3+ messages in thread
From: Conor Dooley @ 2023-06-30 18:39 UTC (permalink / raw)
To: Song Shuai
Cc: apatel, aou, leyfoon.tan, linux-kernel, conor.dooley, palmer,
evan, paul.walmsley, greentime.hu, linux-riscv, heiko.stuebner,
ajones
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On Fri, Jun 30, 2023 at 06:59:38PM +0800, Song Shuai wrote:
> When only the ACPI tables are passed to kernel, the tiny devictree created
> by EFI Stub doesn't provide cpu nodes.
>
> While if append the "acpi=off" to kernel cmdline to disable ACPI for kernel
> the BUG_ON() in of_parse_and_init_cpus() indicates there's no boot cpu
> found in the devicetree, not there're no cpu nodes in the devicetree.
>
> Add BUG_ON() in the first place of of_parse_and_init_cpus() to make it clear.
>
> Signed-off-by: Song Shuai <suagrfillet@gmail.com>
I'm still not really convinced that this is needed - not finding the
boot CPU is a strong a hint as any that your DT is completely broken.
Especially if you intentionally go out of your way to disable ACPI on a
system that requires it to boot.
I'll leave it up to Palmer or whoever to determine whether this is a
valuable change. Code change itself much improved though, thanks - I'd
give an R-b/A-b other than that I question whether there's any value in
adding another BUG_ON(). You could've kept the part of the comment that
explained what the error meant though, but that's not a big deal.
Thanks,
Conor.
> ---
> Changes since V1:
> https://lore.kernel.org/linux-riscv/20230629105839.1160895-1-suagrfillet@gmail.com/
> - revise the commit-msg and move the BUG_ON into of_parse_and_init_cpus() as Conor suggests
>
> ---
> arch/riscv/kernel/smpboot.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index 6ca2b5309aab..04d33afbdf55 100644
> --- a/arch/riscv/kernel/smpboot.c
> +++ b/arch/riscv/kernel/smpboot.c
> @@ -147,6 +147,8 @@ static void __init of_parse_and_init_cpus(void)
> int cpuid = 1;
> int rc;
>
> + BUG_ON(!of_get_next_cpu_node(NULL));
> +
> cpu_set_ops(0);
>
> for_each_of_cpu_node(dn) {
> --
> 2.20.1
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH V2] riscv: Add BUG_ON() for no cpu nodes in devicetree
2023-06-30 18:39 ` Conor Dooley
@ 2023-07-11 22:58 ` Palmer Dabbelt
0 siblings, 0 replies; 3+ messages in thread
From: Palmer Dabbelt @ 2023-07-11 22:58 UTC (permalink / raw)
To: Conor Dooley
Cc: apatel, aou, leyfoon.tan, linux-kernel, Conor Dooley, Evan Green,
Paul Walmsley, suagrfillet, greentime.hu, linux-riscv,
heiko.stuebner, ajones
On Fri, 30 Jun 2023 11:39:24 PDT (-0700), Conor Dooley wrote:
> On Fri, Jun 30, 2023 at 06:59:38PM +0800, Song Shuai wrote:
>> When only the ACPI tables are passed to kernel, the tiny devictree created
>> by EFI Stub doesn't provide cpu nodes.
>>
>> While if append the "acpi=off" to kernel cmdline to disable ACPI for kernel
>> the BUG_ON() in of_parse_and_init_cpus() indicates there's no boot cpu
>> found in the devicetree, not there're no cpu nodes in the devicetree.
>>
>> Add BUG_ON() in the first place of of_parse_and_init_cpus() to make it clear.
>>
>> Signed-off-by: Song Shuai <suagrfillet@gmail.com>
>
> I'm still not really convinced that this is needed - not finding the
> boot CPU is a strong a hint as any that your DT is completely broken.
> Especially if you intentionally go out of your way to disable ACPI on a
> system that requires it to boot.
>
> I'll leave it up to Palmer or whoever to determine whether this is a
> valuable change. Code change itself much improved though, thanks - I'd
> give an R-b/A-b other than that I question whether there's any value in
> adding another BUG_ON(). You could've kept the part of the comment that
> explained what the error meant though, but that's not a big deal.
IIUC this is just reduntant: if the BUG_ON triggers then there's no
CPUs, so we'll end up with no iterations of the loop and thus no found
CPU and thus a BUG_ON. The only difference is the SBI probing, but
that's just poking SBI to turn off spinwait.
So I think we already crash sufficiently on systems with an empty DT.
Sorry if I'm missing something, though?
> Thanks,
> Conor.
>
>> ---
>> Changes since V1:
>> https://lore.kernel.org/linux-riscv/20230629105839.1160895-1-suagrfillet@gmail.com/
>> - revise the commit-msg and move the BUG_ON into of_parse_and_init_cpus() as Conor suggests
>>
>> ---
>> arch/riscv/kernel/smpboot.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
>> index 6ca2b5309aab..04d33afbdf55 100644
>> --- a/arch/riscv/kernel/smpboot.c
>> +++ b/arch/riscv/kernel/smpboot.c
>> @@ -147,6 +147,8 @@ static void __init of_parse_and_init_cpus(void)
>> int cpuid = 1;
>> int rc;
>>
>> + BUG_ON(!of_get_next_cpu_node(NULL));
>> +
>> cpu_set_ops(0);
>>
>> for_each_of_cpu_node(dn) {
>> --
>> 2.20.1
>>
>>
>> _______________________________________________
>> linux-riscv mailing list
>> linux-riscv@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-riscv
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-06-30 18:39 ` Conor Dooley
2023-07-11 22:58 ` Palmer Dabbelt
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