From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Nicolin Chen <nicolinc@nvidia.com>,
joro@8bytes.org, suravee.suthikulpanit@amd.com, will@kernel.org,
robin.murphy@arm.com, robdclark@gmail.com, dwmw2@infradead.org,
baolu.lu@linux.intel.com, agross@kernel.org,
bjorn.andersson@linaro.org, konrad.dybcio@somainline.org,
matthias.bgg@gmail.com, heiko@sntech.de, orsonzhai@gmail.com,
baolin.wang@linux.alibaba.com, zhang.lyra@gmail.com,
thierry.reding@gmail.com, sricharan@codeaurora.org,
yong.wu@mediatek.com, vdumpa@nvidia.com, jonathanh@nvidia.com,
tglx@linutronix.de, shameerali.kolothum.thodi@huawei.com,
thunder.leizhen@huawei.com, christophe.jaillet@wanadoo.fr,
yangyingliang@huawei.com, jon@solid-run.com,
iommu@lists.linux.dev, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-arm-msm@vger.kernel.org,
linux-mediatek@lists.infradead.org,
linux-rockchip@lists.infradead.org, linux-tegra@vger.kernel.org,
virtualization@lists.linux-foundation.org
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
next prev parent reply other threads:[~2022-09-14 9:49 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-13 8:24 [PATCH 0/5] iommu: Define EINVAL as device/domain incompatibility Nicolin Chen
2022-09-13 8:24 ` [PATCH 1/5] iommu/msm: Add missing __disable_clocks calls Nicolin Chen
2022-09-13 8:24 ` [PATCH 2/5] iommu/amd: Drop unnecessary checks in amd_iommu_attach_device() Nicolin Chen
2022-09-13 8:24 ` [PATCH 3/5] iommu: Add return errno rules to ->attach_dev ops Nicolin Chen
2022-09-13 18:41 ` Jeff Johnson
2022-09-13 20:00 ` Nicolin Chen
2022-09-13 8:24 ` [PATCH 4/5] iommu: Regulate errno in ->attach_dev callback functions Nicolin Chen
2022-09-13 12:27 ` Jean-Philippe Brucker
2022-09-13 20:14 ` Nicolin Chen
2022-09-14 9:11 ` Jason Gunthorpe
2022-09-14 9:49 ` Jean-Philippe Brucker [this message]
2022-09-14 17:58 ` Nicolin Chen
2022-09-14 19:53 ` Robin Murphy
2022-09-14 20:55 ` Nicolin Chen
2022-09-13 8:24 ` [PATCH 5/5] iommu: Use EINVAL for incompatible device/domain in ->attach_dev Nicolin Chen
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