From: Jason Gunthorpe <jgg@nvidia.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: Nicolin Chen <nicolinc@nvidia.com>,
will@kernel.org, robin.murphy@arm.com,
alex.williamson@redhat.com, suravee.suthikulpanit@amd.com,
marcan@marcan.st, sven@svenpeter.dev, alyssa@rosenzweig.io,
robdclark@gmail.com, dwmw2@infradead.org,
baolu.lu@linux.intel.com, mjrosato@linux.ibm.com,
gerald.schaefer@linux.ibm.com, orsonzhai@gmail.com,
baolin.wang@linux.alibaba.com, zhang.lyra@gmail.com,
thierry.reding@gmail.com, vdumpa@nvidia.com,
jonathanh@nvidia.com, jean-philippe@linaro.org,
cohuck@redhat.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, asahi@lists.linux.dev,
linux-arm-kernel@lists.infradead.org,
linux-arm-msm@vger.kernel.org, linux-s390@vger.kernel.org,
linux-tegra@vger.kernel.org,
virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
kevin.tian@intel.com
Subject: Re: [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group
Date: Wed, 7 Sep 2022 10:47:39 -0300 [thread overview]
Message-ID: <Yxig+zfA2Pr4vk6K@nvidia.com> (raw)
In-Reply-To: <YxiRkm7qgQ4k+PIG@8bytes.org>
On Wed, Sep 07, 2022 at 02:41:54PM +0200, Joerg Roedel wrote:
> On Mon, Aug 15, 2022 at 11:14:33AM -0700, Nicolin Chen wrote:
> > Provide a dedicated errno from the IOMMU driver during attach that the
> > reason attached failed is because of domain incompatability. EMEDIUMTYPE
> > is chosen because it is never used within the iommu subsystem today and
> > evokes a sense that the 'medium' aka the domain is incompatible.
>
> I am not a fan of re-using EMEDIUMTYPE or any other special value. What
> is needed here in EINVAL, but with a way to tell the caller which of the
> function parameters is actually invalid.
Using errnos to indicate the nature of failure is a well established
unix practice, it is why we have hundreds of error codes and don't
just return -EINVAL for everything.
What don't you like about it?
Would you be happier if we wrote it like
#define IOMMU_EINCOMPATIBLE_DEVICE xx
Which tells "which of the function parameters is actually invalid" ?
> For that I prefer adding an additional pointer parameter to the attach
> functions in which the reason for the failure can be communicated up the
> chain.
That sounds like OS/2 :\
Jason
WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: linux-s390@vger.kernel.org, marcan@marcan.st,
mjrosato@linux.ibm.com, linux-kernel@vger.kernel.org,
thierry.reding@gmail.com, will@kernel.org, alyssa@rosenzweig.io,
jean-philippe@linaro.org, kvm@vger.kernel.org,
zhang.lyra@gmail.com, jon@solid-run.com, jonathanh@nvidia.com,
iommu@lists.linux.dev, Nicolin Chen <nicolinc@nvidia.com>,
yangyingliang@huawei.com, orsonzhai@gmail.com,
gerald.schaefer@linux.ibm.com, kevin.tian@intel.com,
sven@svenpeter.dev, linux-arm-msm@vger.kernel.org,
christophe.jaillet@wanadoo.fr, baolin.wang@linux.alibaba.com,
thunder.leizhen@huawei.com, linux-tegra@vger.kernel.org,
tglx@linutronix.de, virtualization@lists.linux-foundation.org,
linux-arm-kernel@lists.infradead.org, dwmw2@infradead.org,
cohuck@redhat.com, alex.williamson@redhat.com,
shameerali.kolothum.thodi@huawei.com, robdclark@gmail.com,
asahi@lists.linux.dev, suravee.suthikulpanit@amd.com,
robin.murphy@arm.com, baolu.lu@linux.intel.com
Subject: Re: [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group
Date: Wed, 7 Sep 2022 10:47:39 -0300 [thread overview]
Message-ID: <Yxig+zfA2Pr4vk6K@nvidia.com> (raw)
In-Reply-To: <YxiRkm7qgQ4k+PIG@8bytes.org>
On Wed, Sep 07, 2022 at 02:41:54PM +0200, Joerg Roedel wrote:
> On Mon, Aug 15, 2022 at 11:14:33AM -0700, Nicolin Chen wrote:
> > Provide a dedicated errno from the IOMMU driver during attach that the
> > reason attached failed is because of domain incompatability. EMEDIUMTYPE
> > is chosen because it is never used within the iommu subsystem today and
> > evokes a sense that the 'medium' aka the domain is incompatible.
>
> I am not a fan of re-using EMEDIUMTYPE or any other special value. What
> is needed here in EINVAL, but with a way to tell the caller which of the
> function parameters is actually invalid.
Using errnos to indicate the nature of failure is a well established
unix practice, it is why we have hundreds of error codes and don't
just return -EINVAL for everything.
What don't you like about it?
Would you be happier if we wrote it like
#define IOMMU_EINCOMPATIBLE_DEVICE xx
Which tells "which of the function parameters is actually invalid" ?
> For that I prefer adding an additional pointer parameter to the attach
> functions in which the reason for the failure can be communicated up the
> chain.
That sounds like OS/2 :\
Jason
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-09-07 13:47 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-15 18:14 [PATCH v6 0/5] Simplify vfio_iommu_type1 attach/detach routine Nicolin Chen
2022-08-15 18:14 ` Nicolin Chen
2022-08-15 18:14 ` [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group Nicolin Chen
2022-08-15 18:14 ` Nicolin Chen
2022-09-07 12:41 ` Joerg Roedel
2022-09-07 12:41 ` Joerg Roedel
2022-09-07 12:41 ` Joerg Roedel
2022-09-07 13:47 ` Jason Gunthorpe [this message]
2022-09-07 13:47 ` Jason Gunthorpe
2022-09-07 14:06 ` Joerg Roedel
2022-09-07 14:06 ` Joerg Roedel
2022-09-07 14:06 ` Joerg Roedel
2022-09-07 17:10 ` Jason Gunthorpe
2022-09-07 17:10 ` Jason Gunthorpe
2022-09-08 13:28 ` Joerg Roedel
2022-09-08 13:28 ` Joerg Roedel
2022-09-08 13:28 ` Joerg Roedel
2022-09-08 16:14 ` Jason Gunthorpe
2022-09-08 16:14 ` Jason Gunthorpe
2022-09-09 3:17 ` Nicolin Chen
2022-09-09 3:17 ` Nicolin Chen
2022-09-09 5:00 ` Tian, Kevin
2022-09-09 5:00 ` Tian, Kevin
2022-09-09 5:00 ` Tian, Kevin
2022-09-09 12:07 ` Jason Gunthorpe
2022-09-09 12:07 ` Jason Gunthorpe
2022-09-13 2:22 ` Tian, Kevin
2022-09-13 2:22 ` Tian, Kevin
2022-09-13 2:22 ` Tian, Kevin
2022-09-13 5:07 ` Nicolin Chen
2022-09-13 5:07 ` Nicolin Chen
2022-09-07 14:23 ` Robin Murphy
2022-09-07 14:23 ` Robin Murphy
2022-09-07 14:23 ` Robin Murphy
2022-09-07 17:00 ` Jason Gunthorpe
2022-09-07 17:00 ` Jason Gunthorpe
2022-09-07 19:41 ` Robin Murphy
2022-09-07 19:41 ` Robin Murphy
2022-09-07 19:41 ` Robin Murphy
2022-09-08 0:43 ` Jason Gunthorpe
2022-09-08 0:43 ` Jason Gunthorpe
2022-09-08 9:30 ` Tian, Kevin
2022-09-08 9:30 ` Tian, Kevin
2022-09-08 9:30 ` Tian, Kevin
2022-09-08 12:08 ` Jason Gunthorpe
2022-09-08 12:08 ` Jason Gunthorpe
2022-09-10 23:35 ` Nicolin Chen
2022-09-10 23:35 ` Nicolin Chen
2022-09-13 2:24 ` Tian, Kevin
2022-09-13 2:24 ` Tian, Kevin
2022-09-13 2:24 ` Tian, Kevin
2022-09-13 8:36 ` Nicolin Chen
2022-09-13 8:36 ` Nicolin Chen
2022-09-08 9:54 ` Tian, Kevin
2022-09-08 9:54 ` Tian, Kevin
2022-09-08 9:54 ` Tian, Kevin
2022-09-08 10:25 ` Robin Murphy
2022-09-08 10:25 ` Robin Murphy
2022-09-08 10:25 ` Robin Murphy
2022-08-15 18:14 ` [PATCH v6 2/5] vfio/iommu_type1: Prefer to reuse domains vs match enforced cache coherency Nicolin Chen
2022-08-15 18:14 ` Nicolin Chen
2022-08-15 18:14 ` [PATCH v6 3/5] vfio/iommu_type1: Remove the domain->ops comparison Nicolin Chen
2022-08-15 18:14 ` Nicolin Chen
2022-08-15 18:14 ` [PATCH v6 4/5] vfio/iommu_type1: Clean up update_dirty_scope in detach_group() Nicolin Chen
2022-08-15 18:14 ` Nicolin Chen
2022-08-15 18:14 ` [PATCH v6 5/5] vfio/iommu_type1: Simplify group attachment Nicolin Chen
2022-08-15 18:14 ` Nicolin Chen
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