From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: heiko@sntech.de, konrad.dybcio@somainline.org,
bjorn.andersson@linaro.org, linux-tegra@vger.kernel.org,
thierry.reding@gmail.com, will@kernel.org, zhang.lyra@gmail.com,
joro@8bytes.org, jon@solid-run.com, jonathanh@nvidia.com,
linux-rockchip@lists.infradead.org, iommu@lists.linux.dev,
agross@kernel.org, Nicolin Chen <nicolinc@nvidia.com>,
linux-arm-kernel@lists.infradead.org, yangyingliang@huawei.com,
orsonzhai@gmail.com, dwmw2@infradead.org,
linux-arm-msm@vger.kernel.org, vdumpa@nvidia.com,
christophe.jaillet@wanadoo.fr, baolin.wang@linux.alibaba.com,
thunder.leizhen@huawei.com, matthias.bgg@gmail.com,
tglx@linutronix.de, virtualization@lists.linux-foundation.org,
yong.wu@mediatek.com, robin.murphy@arm.com,
linux-kernel@vger.kernel.org,
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suravee.suthikulpanit@amd.com,
linux-mediatek@lists.infradead.org, sricharan@codeaurora.org,
baolu.lu@linux.intel.com
Subject: Re: [PATCH 4/5] iommu: Regulate errno in ->attach_dev callback functions
Date: Wed, 14 Sep 2022 10:49:42 +0100 [thread overview]
Message-ID: <YyGjtsB2Yq4fQICS@myrica> (raw)
In-Reply-To: <YyGaqsXSDMn8R12R@nvidia.com>
On Wed, Sep 14, 2022 at 06:11:06AM -0300, Jason Gunthorpe wrote:
> On Tue, Sep 13, 2022 at 01:27:03PM +0100, Jean-Philippe Brucker wrote:
> > I think in the future it will be too easy to forget about the constrained
> > return value of attach() while modifying some other part of the driver,
> > and let an external helper return EINVAL. So I'd rather not propagate ret
> > from outside of viommu_domain_attach() and finalise().
>
> Fortunately, if -EINVAL is wrongly returned it only creates an
> inefficiency, not a functional problem. So we do not need to be
> precise here.
Ah fair. In that case the attach_dev() documentation should indicate that
EINVAL is a hint, so that callers don't rely on it (currently words "must"
and "exclusively" indicate that returning EINVAL for anything other than
device-domain incompatibility is unacceptable). The virtio-iommu
implementation may well return EINVAL from the virtio stack or from the
host response.
Thanks,
Jean
>
> > Since we can't guarantee that APIs like virtio or ida won't ever return
> > EINVAL, we should set all return values:
>
> I dislike this alot, it squashes all return codes to try to optimize
> an obscure failure path :(
>
> Jason
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next prev parent reply other threads:[~2022-09-14 9:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220913082448.31120-1-nicolinc@nvidia.com>
[not found] ` <20220913082448.31120-5-nicolinc@nvidia.com>
2022-09-13 12:27 ` [PATCH 4/5] iommu: Regulate errno in ->attach_dev callback functions Jean-Philippe Brucker
[not found] ` <YyGaqsXSDMn8R12R@nvidia.com>
2022-09-14 9:49 ` Jean-Philippe Brucker [this message]
[not found] ` <YyIWQ6rX6AR9KX5E@Asurada-Nvidia>
2022-09-14 19:53 ` Robin Murphy
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