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From: Jason Gunthorpe <jgg@nvidia.com>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
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 06:11:06 -0300	[thread overview]
Message-ID: <YyGaqsXSDMn8R12R@nvidia.com> (raw)
In-Reply-To: <YyB3F/o3RfymqiFW@myrica>

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.

> 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

WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
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 06:11:06 -0300	[thread overview]
Message-ID: <YyGaqsXSDMn8R12R@nvidia.com> (raw)
In-Reply-To: <YyB3F/o3RfymqiFW@myrica>

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.

> 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

_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip

WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
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, 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,
	shameerali.kolothum.thodi@huawei.com, robdclark@gmail.com,
	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 06:11:06 -0300	[thread overview]
Message-ID: <YyGaqsXSDMn8R12R@nvidia.com> (raw)
In-Reply-To: <YyB3F/o3RfymqiFW@myrica>

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.

> 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

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2022-09-14  9:22 UTC|newest]

Thread overview: 48+ 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 ` Nicolin Chen
2022-09-13  8:24 ` Nicolin Chen
2022-09-13  8:24 ` [PATCH 1/5] iommu/msm: Add missing __disable_clocks calls Nicolin Chen
2022-09-13  8:24   ` Nicolin Chen
2022-09-13  8:24   ` 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   ` Nicolin Chen
2022-09-13  8:24   ` Nicolin Chen
2022-09-13  8:24 ` [PATCH 3/5] iommu: Add return errno rules to ->attach_dev ops Nicolin Chen
2022-09-13  8:24   ` Nicolin Chen
2022-09-13  8:24   ` Nicolin Chen
2022-09-13 18:41   ` Jeff Johnson
2022-09-13 18:41     ` Jeff Johnson
2022-09-13 18:41     ` Jeff Johnson
2022-09-13 20:00     ` Nicolin Chen
2022-09-13 20:00       ` Nicolin Chen
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  8:24   ` Nicolin Chen
2022-09-13  8:24   ` Nicolin Chen
2022-09-13 12:27   ` Jean-Philippe Brucker
2022-09-13 12:27     ` Jean-Philippe Brucker
2022-09-13 12:27     ` Jean-Philippe Brucker
2022-09-13 12:27     ` Jean-Philippe Brucker
2022-09-13 20:14     ` Nicolin Chen
2022-09-13 20:14       ` Nicolin Chen
2022-09-13 20:14       ` Nicolin Chen
2022-09-14  9:11     ` Jason Gunthorpe [this message]
2022-09-14  9:11       ` Jason Gunthorpe
2022-09-14  9:11       ` Jason Gunthorpe
2022-09-14  9:49       ` Jean-Philippe Brucker
2022-09-14  9:49         ` Jean-Philippe Brucker
2022-09-14  9:49         ` Jean-Philippe Brucker
2022-09-14  9:49         ` Jean-Philippe Brucker
2022-09-14 17:58         ` Nicolin Chen
2022-09-14 17:58           ` Nicolin Chen
2022-09-14 17:58           ` Nicolin Chen
2022-09-14 19:53           ` Robin Murphy
2022-09-14 19:53             ` Robin Murphy
2022-09-14 19:53             ` Robin Murphy
2022-09-14 19:53             ` Robin Murphy
2022-09-14 20:55             ` Nicolin Chen
2022-09-14 20:55               ` Nicolin Chen
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
2022-09-13  8:24   ` Nicolin Chen
2022-09-13  8:24   ` Nicolin Chen

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