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From: Thomas Gleixner <tglx@kernel.org>
To: Guixin Liu <kanie@linux.alibaba.com>, Bjorn Helgaas
 <bhelgaas@google.com>, Lorenzo Pieralisi <lpieralisi@kernel.org>, Marc
 Zyngier <maz@kernel.org>, Jonathan Cameron <jonathan.cameron@huawei.com>,
 Inochi Amaoto <inochiama@gmail.com>, Nam Cao <namcao@linutronix.de>,
 Shradha Gupta <shradhagupta@linux.microsoft.com>, Randy Dunlap
 <rdunlap@infradead.org>
Cc: Xunlei Pang <xlpang@linux.alibaba.com>, oliver.yang@linux.alibaba.com,
 linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH 1/2] genirq/msi: Introduce update hwsize helper
In-Reply-To: <20260324014754.4973-2-kanie@linux.alibaba.com>
References: <20260324014754.4973-1-kanie@linux.alibaba.com>
 <20260324014754.4973-2-kanie@linux.alibaba.com>
Date: Wed, 25 Mar 2026 09:15:42 +0100
Message-ID: <87jyv0fhox.ffs@tglx>
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On Tue, Mar 24 2026 at 09:47, Guixin Liu wrote:
> +int msi_domain_update_hwsize(struct device *dev, unsigned int domid,
> +			     unsigned int hwsize_new)
> +{
> +	struct msi_domain_info *info;
> +	struct irq_domain *domain;
> +
> +	if (hwsize_new > MSI_XA_DOMAIN_SIZE)
> +		return -EINVAL;
> +	if (!hwsize_new)
> +		hwsize_new = MSI_XA_DOMAIN_SIZE;
> +
> +	domain = msi_get_device_domain(dev, domid);
> +	if (!domain)
> +		return -ENODEV;
> +
> +	info = domain->host_data;
> +	if (hwsize_new != info->hwsize)
> +		info->hwsize = hwsize_new;

This is incorrect because the underlying irqdomain has been created with
the original hardware size. So just fiddling with info->hwsize results
in inconsistent state.