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From:   Tom Murphy <tmurphy@arista.com>
Date:   Mon, 15 Apr 2019 19:18:21 +0100
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Subject: Re: [PATCH 5/9] iommu/amd: Implement .flush_np_cache
To:     Christoph Hellwig <hch@infradead.org>, joerg.roedel@amd.com
Cc:     iommu@lists.linux-foundation.org, Heiko Stuebner <heiko@sntech.de>,
        Will Deacon <will.deacon@arm.com>,
        David Brown <david.brown@linaro.org>,
        linux-samsung-soc@vger.kernel.org,
        Dmitry Safonov <dima@arista.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        linux-rockchip@lists.infradead.org, Kukjin Kim <kgene@kernel.org>,
        Andy Gross <andy.gross@linaro.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
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        Matthias Brugger <matthias.bgg@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Tom Murphy <murphyt7@tcd.ie>,
        Robin Murphy <robin.murphy@arm.com>
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This is a cut and paste from the current amd_iommu driver. I really
have no idea if it's a good idea or not. It looks like
joerg.roedel@amd.com might be the person to ask.

@Joerg Roedel should we keep this?

On Mon, Apr 15, 2019 at 7:33 AM Christoph Hellwig <hch@infradead.org> wrote:
>
> > +static void amd_iommu_flush_np_cache(struct iommu_domain *domain,
> > +             unsigned long iova, size_t size)
> > +{
> > +     struct protection_domain *dom = to_pdomain(domain);
> > +
> > +     if (unlikely(amd_iommu_np_cache)) {
>
> Is this case really so unlikely that it needs a static branch prediction
> hint?