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From: Jacob Pan <email@example.com>
To: Jean-Philippe Brucker <firstname.lastname@example.org>
Cc: Joerg Roedel <email@example.com>,
Subject: Re: [PATCH 1/1] iommu: Bind process address spaces to devices
Date: Thu, 28 Feb 2019 10:32:52 -0800 [thread overview]
Message-ID: <20190228103252.69715c67@jacob-builder> (raw)
On Thu, 28 Feb 2019 12:19:22 +0000
Jean-Philippe Brucker <firstname.lastname@example.org> wrote:
> On 27/02/2019 21:41, Jacob Pan wrote:
> > On Tue, 26 Feb 2019 12:17:43 +0100
> > Joerg Roedel <email@example.com> wrote:
> >> Hi Jean-Philippe,
> >> Thanks for the patch! I think this is getting close to be applied
> >> after the next merge window.
> >> On Wed, Feb 20, 2019 at 02:27:59PM +0000, Jean-Philippe Brucker
> >> wrote:
> >>> +int iommu_sva_bind_device(struct device *dev, struct mm_struct
> >>> *mm, int *pasid,
> >>> + iommu_mm_exit_handler_t mm_exit, void
> >>> *drvdata)
> >> I think we are better of with introducing a sva-bind handle which
> >> can be used to extend and further configure the binding done with
> >> this function.
> >> How about a 'struct iommu_sva' with an iommu-private definition
> >> that is returned by this function:
> >> struct iommu_sva *iommu_sva_bind_device(struct device *dev,
> >> struct mm_struct
> >> *mm);
> > Just trying to understand how to use this API.
> > So if we bind the same mm to two different devices, we should get
> > two different iommu_sva handle, right?
> Yes, the iommu_sva handle is the bond between one mm and one device,
> so you will get two different handles.
> > I think intel-svm still needs a flag argument for supervisor pasid
> > etc. Other than that, I think both interface should work for vt-d.
> Is supervisor PASID still needed now that we have auxiliary domains,
> and now that VT-d supports nested IOVA? You could have private kernel
> address spaces through auxiliary domains, or simply use DMA API as
> usual with PASID#0. I've been reluctant to make that feature common
> because it looks risky - gives full access to the kernel address
> space to devices and no notification on mapping change.
It is still in the VT-d spec. Ashok will be able to answer this
> > Another question is that for nested SVA, we will need to bind guest
> > mm. Do you think we should try to reuse this or have it separate? I
> > am working on a separate API for now.
> I also think it should be separate. That bind() operation is performed
> on an auxiliary domain, I guess?
yes the 2nd level is retrieved from aux domain for mdev, but for pdev,
2nd level comes from rid2pasid/default domain.
> >> and the corresponding unbind function:
> >> int iommu_sva_unbind_device(struct iommu_sva* *handle);
> >> (Btw, does this need to return and int? Can unbinding fail?).
> >> With that in place we can implement and extentable API base on the
> >> handle:
> >> int iommu_sva_get_pasid(struct iommu_sva *handle);
> > If multiple bind to the same mm gets multiple handles, this API
> > should retrieve the same pasid for different handle?
> > Just curious why making
> > the handle private instead of returning the pasid value in the
> > handle?
> I don't have a strong objection against that. One reason to have an
> accessor is that the PASID is freed on mm_exit, so until the device
> driver calls unbind(), the PASID contained in the handle is stale (and
> the accessor returns PASID_INVALID). But that's a bit pedantic, the
> device driver should know that the handle is stale since it got
> notified of it. Having an accessor might also help tracking uses of
> the handle in the kernel, and make future API modifications easier.
> >> void iommu_sva_set_exit_handler(struct iommu_sva *handle,
> >> iommu_mm_exit_handler_t
> >> mm_exit);
> >> I think at least the AMD IOMMU driver needs more call-backs like a
> >> handler that is invoked when a fault can not be resolved. And there
> >> might be others in the future, putting them all in the parameter
> >> list of the bind function doesn't scale well.
> >> Regards,
> >> Joerg
next prev parent reply other threads:[~2019-02-28 18:30 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-20 14:27 [PATCH 0/1] IOMMU SVA device driver interface Jean-Philippe Brucker
2019-02-20 14:27 ` [PATCH 1/1] iommu: Bind process address spaces to devices Jean-Philippe Brucker
2019-02-26 11:17 ` Joerg Roedel
2019-02-26 12:49 ` Jean-Philippe Brucker
2019-02-26 13:02 ` Joerg Roedel
2019-02-27 21:41 ` Jacob Pan
2019-02-28 1:10 ` Tian, Kevin
2019-02-28 18:53 ` Jacob Pan
2019-02-28 12:19 ` Jean-Philippe Brucker
2019-02-28 18:32 ` Jacob Pan [this message]
2019-02-28 14:09 ` Joerg Roedel
2019-02-28 21:15 ` Jacob Pan
2019-02-28 22:04 ` Raj, Ashok
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