linux-kernel - Re: [PATCH 5/9] iommu/amd: Implement .flush_np

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Date:   Mon, 15 Apr 2019 19:18:21 +0100
From:   Tom Murphy <tmurphy@...sta.com>
To:     Christoph Hellwig <hch@...radead.org>, joerg.roedel@....com
Cc:     iommu@...ts.linux-foundation.org, Heiko Stuebner <heiko@...ech.de>,
        Will Deacon <will.deacon@....com>,
        David Brown <david.brown@...aro.org>,
        linux-samsung-soc@...r.kernel.org,
        Dmitry Safonov <dima@...sta.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-rockchip@...ts.infradead.org, Kukjin Kim <kgene@...nel.org>,
        Andy Gross <andy.gross@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>,
        linux-arm-msm@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        Matthias Brugger <matthias.bgg@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Tom Murphy <murphyt7@....ie>,
        Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH 5/9] iommu/amd: Implement .flush_np_cache

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@....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@...radead.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?