From: Andrew Jones <ajones@ventanamicro.com>
To: Charlie Jenkins <charlie@rivosinc.com>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
paul.walmsley@sifive.com, palmer@dabbelt.com,
jesse@rivosinc.com, Anup Patel <apatel@ventanamicro.com>
Subject: Re: [PATCH 7/9] riscv: Prepare for unaligned access type table lookups
Date: Mon, 10 Feb 2025 10:43:18 +0100 [thread overview]
Message-ID: <20250210-51cedc94f4cba8c96516adc5@orel> (raw)
In-Reply-To: <Z6ax7B45OsGerjfA@ghost>
On Fri, Feb 07, 2025 at 05:22:52PM -0800, Charlie Jenkins wrote:
> On Fri, Feb 07, 2025 at 05:19:47PM +0100, Andrew Jones wrote:
> > Probing unaligned accesses on boot is time consuming. Provide a
> > function which will be used to look up the access type in a table
> > by id registers. Vendors which provide table entries can then skip
> > the probing.
>
> The access checker in my experience is only time consuming on slow
> hardware. Hardware that supports fast unaligned accesses isn't really
> impacted by this?
That's true, but...
> Avoiding a list of hardware that has slow/fast
> unaligned accesses in the kernel was the main reason for dynamically
> checking.
...I'm not sure why we should try to avoid determining hardware support
by its description when a description can be provided.
> We did introduce the config option to compile the kernel with
> assumed slow/fast accesses, which of course has the downside of
> recompiling the kernel and I assume that you already considered that.
yup
>
> Instead of having a table in the kernel, something that would be more
> platform agnostic would be to have an extension that signals this
> information. That seems like it would accomplish the same goal and
> leverage the existing infrastructure in the kernel, albeit with the need
> to make a new extension.
Yes, I agree that another profile "named feature" may be the best
approach. I'll consider proposing one, but [1] implies there may be
some resistance to creating something like that.
[1] https://github.com/riscv/riscv-isa-manual/issues/1611
Thanks,
drew
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next prev parent reply other threads:[~2025-02-10 9:43 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-07 16:19 [PATCH 0/9] riscv: Unaligned access speed probing fixes and skipping Andrew Jones
2025-02-07 16:19 ` [PATCH 1/9] riscv: Annotate unaligned access init functions Andrew Jones
2025-02-13 12:59 ` Alexandre Ghiti
2025-02-07 16:19 ` [PATCH 2/9] riscv: Fix riscv_online_cpu_vec Andrew Jones
2025-02-07 16:47 ` Clément Léger
2025-02-07 17:08 ` Andrew Jones
2025-02-07 17:43 ` Clément Léger
2025-02-07 18:08 ` Andrew Jones
2025-02-13 13:02 ` Alexandre Ghiti
2025-02-07 16:19 ` [PATCH 3/9] riscv: Fix check_unaligned_access_all_cpus Andrew Jones
2025-02-13 13:12 ` Alexandre Ghiti
2025-02-07 16:19 ` [PATCH 4/9] riscv: Change check_unaligned_access_speed_all_cpus to void Andrew Jones
2025-02-07 16:42 ` Clément Léger
2025-02-13 13:15 ` Alexandre Ghiti
2025-02-07 16:19 ` [PATCH 5/9] riscv: Fix set up of cpu hotplug callbacks Andrew Jones
2025-02-07 16:44 ` Clément Léger
2025-02-13 13:25 ` Alexandre Ghiti
2025-02-13 13:33 ` Alexandre Ghiti
2025-02-07 16:19 ` [PATCH 6/9] riscv: Fix set up of vector cpu hotplug callback Andrew Jones
2025-02-07 17:36 ` Clément Léger
2025-02-07 18:15 ` Andrew Jones
2025-02-13 13:28 ` Alexandre Ghiti
2025-02-07 16:19 ` [PATCH 7/9] riscv: Prepare for unaligned access type table lookups Andrew Jones
2025-02-08 1:22 ` Charlie Jenkins
2025-02-10 9:43 ` Andrew Jones [this message]
2025-02-10 17:10 ` Charlie Jenkins
2025-02-10 10:16 ` Anup Patel
2025-02-10 11:07 ` Clément Léger
2025-02-10 14:06 ` Andrew Jones
2025-02-10 14:20 ` Clément Léger
2025-02-10 17:20 ` Charlie Jenkins
2025-02-10 20:42 ` Clément Léger
2025-02-10 20:53 ` Charlie Jenkins
2025-02-10 20:57 ` Clément Léger
2025-02-10 21:13 ` Charlie Jenkins
2025-02-11 4:26 ` Anup Patel
2025-02-11 8:37 ` Clément Léger
2025-02-11 18:09 ` Palmer Dabbelt
2025-02-10 17:19 ` Charlie Jenkins
2025-02-10 20:37 ` Clément Léger
2025-02-11 9:04 ` Andrew Jones
2025-02-07 16:19 ` [PATCH 8/9] riscv: Implement check_unaligned_access_table Andrew Jones
2025-02-07 16:19 ` [PATCH 9/9] riscv: Add Ventana unaligned access table entries Andrew Jones
2025-02-07 18:10 ` [PATCH 8/9] riscv: Implement check_unaligned_access_table Andrew Jones
2025-02-07 18:19 ` Andrew Jones
2025-02-08 7:59 ` [PATCH 0/9] riscv: Unaligned access speed probing fixes and skipping Anup Patel
2025-02-10 9:26 ` Andrew Jones
2025-02-10 9:58 ` Anup Patel
2025-02-10 11:01 ` Andrew Jones
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