linux-kernel - Re: [bug report] iommu_dma_unmap_sg() is very slow then running IO from remote numa node

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Date:   Thu, 22 Jul 2021 13:53:59 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     John Garry <john.garry@...wei.com>
Cc:     Ming Lei <ming.lei@...hat.com>,
        Robin Murphy <robin.murphy@....com>,
        iommu@...ts.linux-foundation.org, Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [bug report] iommu_dma_unmap_sg() is very slow then running IO
 from remote numa node

On 2021-07-22 12:12, John Garry wrote:

Hi John,

[...]

>     Your kernel log should show:
>     [    0.000000] GICv3: Pseudo-NMIs enabled using forced ICC_PMR_EL1
> synchronisation

Unrelated, but you seem to be running with ICC_CTLR_EL3.PMHE set,
which makes the overhead of pseudo-NMIs much higher than it should be
(you take a DSB SY on each interrupt unmasking).

If you are not using 1:N distribution of SPIs on the secure side,
consider turning that off in your firmware. This should make NMIs
slightly more pleasant to use.

         M.
-- 
Jazz is not dead. It just smells funny...