linux-kernel - RE: [PATCH v2 03/16] iommu: introduce iommu invalidate API function

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Date:   Wed, 11 Oct 2017 11:54:52 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     Joerg Roedel <joro@...tes.org>
CC:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        "Lan, Tianyu" <tianyu.lan@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Liu, Yi L" <yi.l.liu@...ux.intel.com>
Subject: RE: [PATCH v2 03/16] iommu: introduce iommu invalidate API function

> On Wed, Oct 11, 2017 at 07:54:32AM +0000, Liu, Yi L wrote:
> > I agree that iommu_invalidate() is too generic. Additionally, also
> > better to avoid making it svm specific.
> 
> I also don't like to name the functions after the Intel feature, but I failed to come up
> with a better alternative so far. The only one I can come up with for now would be
> 'iovm', so the function name would be iommu_iovm_invalidate().

[Liu, Yi L] Actually, I'm not against 'SVM' terms. Just want to make it be compatible
with future usage in non-SVM scenario.

> On the other side, the ARM guys also already call the feature set 'SVM', despite it
> being ambiguous and Intel specific. I don't have a strong opinion on the naming.
> 
> > The reason we introduce this API is in vSVM case is that guest owns
> > the first level page table(vtd). If we use similar mechanism for
> > vIOVA, then we also need to passdown guest's vIOVA tlb flush.
> >
> > Since it is to expose an API for iommu tlb flushes requests from
> > userspace/guest which is out of iommu. How about naming it as
> > iommu_tlb_external_invalidate()?
> 
> If you only read the function name, 'external' could mean everything. It is not clear

[Liu, Yi L] Agree, 'external' is also unclear.

> from the name when to use this function. So something like
> iommu_iovm_invalidate() is better.
> 

[Liu, Yi L] I didn't quite get 'iovm' mean. Can you explain a bit about the idea?

Thanks,
Yi L