linux-kernel - RE: [PATCH v4 05/22] iommu: introduce iommu invalidate API function

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Date:   Sat, 28 Apr 2018 02:41:08 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
CC:     "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        "David Woodhouse" <dwmw2@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Jean Delvare <khali@...ux-fr.org>,
        Christoph Hellwig <hch@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        "Liu, Yi L" <yi.l.liu@...ux.intel.com>,
        "Liu@...rya.localdomain" <Liu@...rya.localdomain>
Subject: RE: [PATCH v4 05/22] iommu: introduce iommu invalidate API function

> From: Jean-Philippe Brucker [mailto:jean-philippe.brucker@....com]
> Sent: Saturday, April 28, 2018 2:08 AM
> 
> [...]
> >> If this corresponds to QI_GRAN_ALL_ALL in patch 9, the comment should
> >> be "Cache of all PASIDs"? Or maybe "all entries for all PASIDs"? Is it
> >> different from GRANU_DOMAIN then?
> > QI_GRAN_ALL_ALL maps to VT-d spec 6.5.2.4, which invalidates all ext
> > TLB cache within a domain. It could reuse GRANU_DOMAIN but I was
> > also trying to match the naming convention in the spec.
> 
> Sorry I don't quite understand the difference between TLB and ext TLB
> invalidation. Can an ext TLB invalidation do everything a TLB can do
> plus some additional parameters (introduced in more recent version of
> the spec), or do they have distinct purposes? I'm trying to understand
> why it needs to be user-visible

distinct purpose though some overlapped effect:

IOTLB invalidate is more for 2nd-level cache on granularity (global/
domain/PSI), with side effect on 1st-level and nested caches (global/
domain).

Extended IOTLB invalidate is specifically for 1st-level and nested
caches on granularity (per-domain: all PASIDs/per PASID/PSI). 

Thanks
Kevin