From: Lu Baolu <baolu.lu@linux.intel.com>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>,
Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: baolu.lu@linux.intel.com, LKML <linux-kernel@vger.kernel.org>,
iommu@lists.linux-foundation.org, Joerg Roedel <joro@8bytes.org>,
Jean-Philippe Brucker <jean-philippe@linaro.com>,
Yi Liu <yi.l.liu@intel.com>, Raj Ashok <ashok.raj@intel.com>,
"Tian, Kevin" <kevin.tian@intel.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Dave Jiang <dave.jiang@intel.com>,
wangzhou1@hisilicon.com, zhangfei.gao@linaro.org,
vkoul@kernel.org
Subject: Re: [PATCH 2/2] iommu/sva: Remove mm parameter from SVA bind API
Date: Wed, 14 Apr 2021 14:22:09 +0800 [thread overview]
Message-ID: <41433d99-e413-f5bf-5279-695dae6c58ba@linux.intel.com> (raw)
In-Reply-To: <20210413170947.35ba9267@jacob-builder>
Hi Jacob,
On 4/14/21 8:09 AM, Jacob Pan wrote:
> Hi Jean,
>
> On Fri, 9 Apr 2021 11:03:05 -0700, Jacob Pan
> <jacob.jun.pan@linux.intel.com> wrote:
>
>>> problems:
>>>
>>> * We don't have a use-case for binding the mm of a remote process (and
>>> it's supposedly difficult for device drivers to do it securely). So
>>> OK, we remove the mm argument from iommu_sva_bind_device() and use the
>>> current mm. But the IOMMU driver isn't going to do
>>> get_task_mm(current) every time it needs the mm being bound, it will
>>> take it from iommu_sva_bind_device(). Likewise iommu_sva_alloc_pasid()
>>> shouldn't need to bother with get_task_mm().
>>>
>>> * cgroup accounting for IOASIDs needs to be on the current task.
>>> Removing the mm parameter from iommu_sva_alloc_pasid() doesn't help
>>> with that. Sure it indicates that iommu_sva_alloc_pasid() needs a
>>> specific task context but that's only for cgroup purpose, and I'd
>>> rather pass the cgroup down from iommu_sva_bind_device() anyway (but am
>>> fine with keeping it within ioasid_alloc() for now). Plus it's an
>>> internal helper, easy for us to check that the callers are doing the
>>> right thing.
>> With the above split, we really just have one allocation function:
>> ioasid_alloc(), so it can manage current cgroup accounting within. Would
>> this work?
> After a few attempts, I don't think the split can work better. I will
> restore the mm parameter and add a warning if mm != current->mm.
I still worry about supervisor pasid allocation.
If we use iommu_sva_alloc_pasid() to allocate a supervisor pasid, which
mm should the pasid be set? I've ever thought about passing &init_mm to
iommu_sva_alloc_pasid(). But if you add "mm != current->mm", this seems
not to work. Or do you prefer a separated interface for supervisor pasid
allocation/free?
Best regards,
baolu
>
> Thanks,
>
> Jacob
>
next prev parent reply other threads:[~2021-04-14 6:32 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-08 17:08 [PATCH 1/2] iommu/sva: Tighten SVA bind API with explicit flags Jacob Pan
2021-04-08 17:08 ` [PATCH 2/2] iommu/sva: Remove mm parameter from SVA bind API Jacob Pan
2021-04-09 10:11 ` Jean-Philippe Brucker
2021-04-09 18:03 ` Jacob Pan
2021-04-14 0:09 ` Jacob Pan
2021-04-14 6:22 ` Lu Baolu [this message]
2021-04-14 11:26 ` Jason Gunthorpe
2021-04-15 5:33 ` Lu Baolu
2021-04-15 11:59 ` Jason Gunthorpe
2021-04-09 12:45 ` Lu Baolu
2021-04-09 18:08 ` Jacob Pan
2021-04-09 10:22 ` [PATCH 1/2] iommu/sva: Tighten SVA bind API with explicit flags Jean-Philippe Brucker
2021-04-09 21:57 ` Jacob Pan
2021-04-09 12:24 ` Lu Baolu
2021-04-13 22:13 ` Jacob Pan
2021-04-13 13:02 ` kernel test robot
2021-04-14 4:11 ` kernel test robot
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