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From: Thomas Gleixner <tglx@linutronix.de>
To: Troy Mitchell <troy.mitchell@linux.dev>,
	Paul Walmsley <pjw@kernel.org>,
	Samuel Holland <samuel.holland@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>
Cc: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	Troy Mitchell <troy.mitchell@linux.dev>
Subject: Re: [PATCH v2] riscv/plic: assign context ID based on hartid
Date: Thu, 13 Nov 2025 14:47:33 +0100	[thread overview]
Message-ID: <87bjl6cadm.ffs@tglx> (raw)
In-Reply-To: <20251027-fix-plic-amp-v2-1-f077b9439112@linux.dev>

On Mon, Oct 27 2025 at 15:03, Troy Mitchell wrote:
> The PLIC driver for OF-based platforms currently assigns 'context_id = i'
> within the context loop. This implies an assumption that all harts are
> numbered contiguously starting from 0.
>
> In Asymmetric Multi-Processing (AMP) systems, where Linux might boot on
> a non-zero hart ID (e.g., hart4), while other harts (e.g., hart0) are
> running a different OS, this assumption is violated. This can lead to
>  different system inadvertently sharing the same
> PLIC enable_base register. Consequently, this causes configuration
> conflicts and incorrect interrupt handling.
>
> Assign the PLIC context ID based on the actual hart ID provided by the
> OF node. This ensures that each hart context maps to a unique enable
> region within the PLIC, thereby resolving conflicts in AMP setups. This
> change preserves the correct behavior on Symmetric Multi-Processing (SMP)
> and Uniprocessor (UP) systems.

Can the RISCV people please have a look at this?

Thanks,

        tglx

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WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de>
To: Troy Mitchell <troy.mitchell@linux.dev>,
	Paul Walmsley <pjw@kernel.org>,
	Samuel Holland <samuel.holland@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>
Cc: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	Troy Mitchell <troy.mitchell@linux.dev>
Subject: Re: [PATCH v2] riscv/plic: assign context ID based on hartid
Date: Thu, 13 Nov 2025 14:47:33 +0100	[thread overview]
Message-ID: <87bjl6cadm.ffs@tglx> (raw)
In-Reply-To: <20251027-fix-plic-amp-v2-1-f077b9439112@linux.dev>

On Mon, Oct 27 2025 at 15:03, Troy Mitchell wrote:
> The PLIC driver for OF-based platforms currently assigns 'context_id = i'
> within the context loop. This implies an assumption that all harts are
> numbered contiguously starting from 0.
>
> In Asymmetric Multi-Processing (AMP) systems, where Linux might boot on
> a non-zero hart ID (e.g., hart4), while other harts (e.g., hart0) are
> running a different OS, this assumption is violated. This can lead to
>  different system inadvertently sharing the same
> PLIC enable_base register. Consequently, this causes configuration
> conflicts and incorrect interrupt handling.
>
> Assign the PLIC context ID based on the actual hart ID provided by the
> OF node. This ensures that each hart context maps to a unique enable
> region within the PLIC, thereby resolving conflicts in AMP setups. This
> change preserves the correct behavior on Symmetric Multi-Processing (SMP)
> and Uniprocessor (UP) systems.

Can the RISCV people please have a look at this?

Thanks,

        tglx

  reply	other threads:[~2025-11-13 13:47 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-10-27  7:03 [PATCH v2] riscv/plic: assign context ID based on hartid Troy Mitchell
2025-10-27  7:03 ` Troy Mitchell
2025-11-13 13:47 ` Thomas Gleixner [this message]
2025-11-13 13:47   ` Thomas Gleixner
2025-11-13 15:18 ` Anup Patel
2025-11-13 15:18   ` Anup Patel

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