linux-kernel - Re: [PATCH 2/9] riscv: Fix riscv_online_cpu

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Message-ID: <20250207-7bcda0b97d4beb9d72de12f7@orel>
Date: Fri, 7 Feb 2025 19:08:17 +0100
From: Andrew Jones <ajones@...tanamicro.com>
To: Clément Léger <cleger@...osinc.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	paul.walmsley@...ive.com, palmer@...belt.com, charlie@...osinc.com, jesse@...osinc.com, 
	Anup Patel <apatel@...tanamicro.com>
Subject: Re: [PATCH 2/9] riscv: Fix riscv_online_cpu_vec

On Fri, Feb 07, 2025 at 06:43:26PM +0100, Clément Léger wrote:
> 
> 
> On 07/02/2025 18:08, Andrew Jones wrote:
> > On Fri, Feb 07, 2025 at 05:47:28PM +0100, Clément Léger wrote:
> >>
> >>
> >> On 07/02/2025 17:19, Andrew Jones wrote:
> >>> We shouldn't probe when we already know vector is unsupported and
> >>> we should probe when we see we don't yet know whether it's supported.
> >>> Furthermore, we should ensure we've set the access type to
> >>> unsupported when we don't have vector at all.
> >>>
> >>> Fixes: e7c9d66e313b ("RISC-V: Report vector unaligned access speed hwprobe")
> >>> Signed-off-by: Andrew Jones <ajones@...tanamicro.com>
> >>> ---
> >>>  arch/riscv/kernel/unaligned_access_speed.c | 6 ++++--
> >>>  1 file changed, 4 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel/unaligned_access_speed.c
> >>> index b7a8ff7ba6df..161964cf2abc 100644
> >>> --- a/arch/riscv/kernel/unaligned_access_speed.c
> >>> +++ b/arch/riscv/kernel/unaligned_access_speed.c
> >>> @@ -367,10 +367,12 @@ static void check_vector_unaligned_access(struct work_struct *work __always_unus
> >>>  
> >>>  static int riscv_online_cpu_vec(unsigned int cpu)
> >>>  {
> >>> -	if (!has_vector())
> >>> +	if (!has_vector()) {
> >>> +		per_cpu(vector_misaligned_access, cpu) = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED;
> >>>  		return 0;
> >>> +	}
> >>>  
> >>> -	if (per_cpu(vector_misaligned_access, cpu) != RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED)
> >>> +	if (per_cpu(vector_misaligned_access, cpu) != RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN)
> >>>  		return 0;
> >>>  
> >>>  	check_vector_unaligned_access_emulated(NULL);
> >>
> >> Hi Andrew,
> >>
> >> Wouldn't it be easier just not to register the hotplug callback in case
> >> !has_vector() ? In which case just set all possible cpus
> >> vector_misaligned_access to RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED
> >> at startup.
> > 
> > We could do that, but I have another use for the hotplug callback that
> > you'll see near the end of the series.
> 
> Ok, I saw patch 7/9.
> 
> BTW, what happened to patch 8 ? I thought it was in my spam but even
> lore.kernel.org does not have it:
> https://lore.kernel.org/linux-riscv/20250207161939.46139-11-ajones@ventanamicro.com/T/#t

I see it on lore for lkml, so linux-riscv dropped it for no good reason...
I'll send patch 8 again (this time with feeling) just to linux-riscv and
we'll see if gets through.

https://lore.kernel.org/all/20250207161939.46139-19-ajones@ventanamicro.com/

Thanks,
drew