linux-kernel - Re: [PATCH v2 2/5] PCI: dwc: Check alloc

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Message-ID: <74af578c79bd09f2111e5438917f2c6e@misterjones.org>
Date:   Tue, 29 Sep 2020 18:29:52 +0100
From:   Marc Zyngier <maz@...terjones.org>
To:     Jisheng Zhang <Jisheng.Zhang@...aptics.com>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Richard Zhu <hongxing.zhu@....com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Yue Wang <yue.wang@...ogic.com>,
        Kevin Hilman <khilman@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Jesper Nilsson <jesper.nilsson@...s.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Xiaowei Song <songxiaowei@...ilicon.com>,
        Binghui Wang <wangbinghui@...ilicon.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stanimir Varbanov <svarbanov@...sol.com>,
        Pratyush Anand <pratyush.anand@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-samsung-soc@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...s.com,
        linux-arm-msm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-amlogic@...ts.infradead.org, linux-omap@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/5] PCI: dwc: Check alloc_page() return value

On 2020-09-24 12:06, Jisheng Zhang wrote:
> We need to check alloc_page() succeed or not before continuing.
> 
> Signed-off-by: Jisheng Zhang <Jisheng.Zhang@...aptics.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c
> b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 0a19de946351..9e04e8ef3aa4 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -303,6 +303,11 @@ void dw_pcie_msi_init(struct pcie_port *pp)
>  	u64 msi_target;
> 
>  	pp->msi_page = alloc_page(GFP_KERNEL);
> +	if (!pp->msi_page) {
> +		dev_err(dev, "Failed to alloc MSI page\n");

A failing allocation will already scream, so there is no need to
add insult to injury.

More importantly, what is this MSI page ever used for? If I remember
well, this is just a random address that never gets written to.

So why do we allocate a page here? Why do we bother with this DMA
mapping?

         M.
-- 
Who you jivin' with that Cosmik Debris?