linux-kernel - Re: [PATCH v1] iommu/amd: flush not present cache in iommu_map

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Date:   Sat, 27 Apr 2019 15:20:35 +0100
From:   Tom Murphy <tmurphy@...sta.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     iommu@...ts.linux-foundation.org, Tom Murphy <murphyt7@....ie>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] iommu/amd: flush not present cache in iommu_map_page

> The iommu_map_page function is called once per physical page that is
> mapped, so in the worst case for every 4k mapping established. So it is
> not the right place to put this check in.

Ah, you're right, that was careless of me.

> From a quick glance this check belongs into the map_sg() and the
> amd_iommu_map() function, but without the dom->updated check.
>
> Besides, to really support systems with np-cache in a way that doesn't
> destroy all performance, the driver also needs range-flushes for IOTLBs.

I am working on another patch to improve the intel iotlb flushing in
the iommu ops patch which should cover this too.

> Currently it can only flush a 4k page of the full address space of a
> domain. But that doesn't mean we shouldn't fix the missing flushes now.
>
> So please re-send the patch with the check at the two places I pointed
> out above.

will do