linux-kernel - Re: [PATCH v7 18/31] arm64: smp: Support non-SGIs for IPIs

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Message-ID: <aGaqCofcXUxAdVAZ@arm.com>
Date: Thu, 3 Jul 2025 17:04:26 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>
Cc: Marc Zyngier <maz@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Will Deacon <will@...nel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Sascha Bischoff <sascha.bischoff@....com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Timothy Hayes <timothy.hayes@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Peter Maydell <peter.maydell@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	Jiri Slaby <jirislaby@...nel.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v7 18/31] arm64: smp: Support non-SGIs for IPIs

On Thu, Jul 03, 2025 at 12:25:08PM +0200, Lorenzo Pieralisi wrote:
> From: Marc Zyngier <maz@...nel.org>
> 
> The arm64 arch has relied so far on GIC architectural software
> generated interrupt (SGIs) to handle IPIs. Those are per-cpu
> software generated interrupts.
> 
> arm64 architecture code that allocates the IPIs virtual IRQs and
> IRQ descriptors was written accordingly.
> 
> On GICv5 systems, IPIs are implemented using LPIs that are not
> per-cpu interrupts - they are just normal routable IRQs.
> 
> Add arch code to set-up IPIs on systems where they are handled
> using normal routable IRQs.
> 
> For those systems, force the IRQ affinity (and make it immutable)
> to the cpu a given IRQ was assigned to.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> [timothy.hayes@....com: fixed ipi/irq conversion, irq flags]
> Signed-off-by: Timothy Hayes <timothy.hayes@....com>
> [lpieralisi: changed affinity set-up, log]
> Signed-off-by: Lorenzo Pieralisi <lpieralisi@...nel.org>
> Cc: Will Deacon <will@...nel.org>
> Cc: Catalin Marinas <catalin.marinas@....com>

Acked-by: Catalin Marinas <catalin.marinas@....com>