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From: Thomas Gleixner <tglx@linutronix.de>
To: Anup Patel <apatel@ventanamicro.com>, Jonathan Corbet <corbet@lwn.net>
Cc: Anup Patel <anup@brainfault.org>,
	Atish Patra <atish.patra@linux.dev>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Alexandre Ghiti <alex@ghiti.fr>,
	Andrew Jones <ajones@ventanamicro.com>,
	linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Anup Patel <apatel@ventanamicro.com>
Subject: Re: [PATCH] irqchip: riscv-imsic: Add kernel parameter to disable IPIs
Date: Mon, 30 Jun 2025 18:09:24 +0200	[thread overview]
Message-ID: <87wm8tmcsr.ffs@tglx> (raw)
In-Reply-To: <20250625161715.1003948-1-apatel@ventanamicro.com>

On Wed, Jun 25 2025 at 21:47, Anup Patel wrote:

$Subject...

https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#patch-subject

Is it that hard?

> When injecting IPIs to a set of harts, the IMSIC IPI support will
> do a separate MMIO write to SETIPNUM_LE register of each target
> hart. This means on a platform where IMSIC is trap-n-emulated,
> there will be N MMIO traps when injecting IPI to N target harts
> hence IPIs based on IMSIC software injected MSI is slow compared
> to the SBI IPI extension.
>
> Add a kernel parameter to disable IPIs in IMSIC driver for platforms
> with trap-n-emulated IMSIC.

Why do you need a kernel parameter for that. If the platform uses trap-n
emulation, then disable the IPI muck automatically, no?

Thanks,

        tglx

WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de>
To: Anup Patel <apatel@ventanamicro.com>, Jonathan Corbet <corbet@lwn.net>
Cc: Anup Patel <anup@brainfault.org>,
	Atish Patra <atish.patra@linux.dev>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Alexandre Ghiti <alex@ghiti.fr>,
	Andrew Jones <ajones@ventanamicro.com>,
	linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Anup Patel <apatel@ventanamicro.com>
Subject: Re: [PATCH] irqchip: riscv-imsic: Add kernel parameter to disable IPIs
Date: Mon, 30 Jun 2025 18:09:24 +0200	[thread overview]
Message-ID: <87wm8tmcsr.ffs@tglx> (raw)
In-Reply-To: <20250625161715.1003948-1-apatel@ventanamicro.com>

On Wed, Jun 25 2025 at 21:47, Anup Patel wrote:

$Subject...

https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#patch-subject

Is it that hard?

> When injecting IPIs to a set of harts, the IMSIC IPI support will
> do a separate MMIO write to SETIPNUM_LE register of each target
> hart. This means on a platform where IMSIC is trap-n-emulated,
> there will be N MMIO traps when injecting IPI to N target harts
> hence IPIs based on IMSIC software injected MSI is slow compared
> to the SBI IPI extension.
>
> Add a kernel parameter to disable IPIs in IMSIC driver for platforms
> with trap-n-emulated IMSIC.

Why do you need a kernel parameter for that. If the platform uses trap-n
emulation, then disable the IPI muck automatically, no?

Thanks,

        tglx

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http://lists.infradead.org/mailman/listinfo/linux-riscv

  reply	other threads:[~2025-06-30 16:09 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-06-25 16:17 [PATCH] irqchip: riscv-imsic: Add kernel parameter to disable IPIs Anup Patel
2025-06-25 16:17 ` Anup Patel
2025-06-30 16:09 ` Thomas Gleixner [this message]
2025-06-30 16:09   ` Thomas Gleixner
2025-07-01  6:30   ` Anup Patel
2025-07-01  6:30     ` Anup Patel
2025-07-01  7:34     ` Thomas Gleixner
2025-07-01  7:34       ` Thomas Gleixner
2025-07-02 11:04       ` Anup Patel
2025-07-02 11:04         ` Anup Patel

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