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From: Thomas Gleixner <tglx@kernel.org>
To: Naman Jain <namjain@linux.microsoft.com>, Ingo Molnar
 <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Dave Hansen
 <dave.hansen@linux.intel.com>, x86@kernel.org, "H . Peter Anvin"
 <hpa@zytor.com>, Wei Liu <wei.liu@kernel.org>, "K . Y . Srinivasan"
 <kys@microsoft.com>, Haiyang Zhang <haiyangz@microsoft.com>, Dexuan Cui
 <decui@microsoft.com>
Cc: Michael Kelley <mhklinux@outlook.com>, Long Li <longli@microsoft.com>,
 Nam Cao <namcao@linutronix.de>, Joerg Roedel <joro@8bytes.org>, Suravee
 Suthikulpanit <suravee.suthikulpanit@amd.com>, Vasant Hegde
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 Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= <kwilczynski@kernel.org>, Manivannan
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 <daniel@quora.org>, linux-hyperv@vger.kernel.org,
 linux-kernel@vger.kernel.org, iommu@lists.linux.dev,
 linux-pci@vger.kernel.org
Subject: Re: [PATCH v3 2/3] x86/irq: Fall back to
 irq_chip_retrigger_hierarchy() in fixup_irqs()
In-Reply-To: <20260907065129.269262-3-namjain@linux.microsoft.com>
References: <20260907065129.269262-1-namjain@linux.microsoft.com>
 <20260907065129.269262-3-namjain@linux.microsoft.com>
Date: Mon, 07 Sep 2026 15:12:44 +0200
Message-ID: <87qzj52oj7.ffs@fw13>
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On Mon, Sep 07 2026 at 06:51, Naman Jain wrote:
> fixup_irqs() re-injects a pending interrupt on its new target CPU by
> looking at the outermost domain chip and invoking its irq_retrigger()
> callback directly. When the outermost chip does not implement
> irq_retrigger(), the pending interrupt is silently dropped, which can
> lead to lost interrupts on CPU hot-unplug.
>
> Keep calling the outermost chip's irq_retrigger() when it is present,
> but fall back to irq_chip_retrigger_hierarchy() otherwise, which walks
> up the interrupt hierarchy until it finds a chip that implements
> irq_retrigger().
>
> While at it, use a scoped guard for desc->lock. VECTOR_RETRIGGERED is
> now set only when the retrigger succeeds instead of unconditionally,
> which is harmless today since apic_retrigger_irq() always returns 1.
>
> Suggested-by: Thomas Gleixner <tglx@kernel.org>
> Reviewed-by: Shradha Gupta <shradhagupta@linux.microsoft.com>
> Signed-off-by: Naman Jain <namjain@linux.microsoft.com>

Reviewed-by: Thomas Gleixner <tglx@kernel.org>