linux-kernel - RE: [PATCH] iommu/iova: Free all CPU rcache for retry when iova alloc failure

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Message-ID: <20220307034927.23159-1-yf.wang@mediatek.com>
Date:   Mon, 7 Mar 2022 11:49:27 +0800
From:   <yf.wang@...iatek.com>
To:     <robin.murphy@....com>
CC:     <Libo.Kang@...iatek.com>, <Ning.Li@...iatek.com>,
        <iommu@...ts.linux-foundation.org>, <joro@...tes.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <matthias.bgg@...il.com>,
        <stable@...r.kernel.org>, <will@...nel.org>,
        <wsd_upstream@...iatek.com>, <yf.wang@...iatek.com>
Subject: RE: [PATCH] iommu/iova: Free all CPU rcache for retry when iova alloc failure

On Fri, 2022-03-04 at 14:03 +0000, Robin Murphy wrote:
> 
> OK, so either there's a mystery bug where IOVAs somehow get freed on 
> offline CPUs, or the hotplug notifier isn't working correctly, or
> you've 
> contrived a situation where alloc_iova_fast() is actually racing
> against 
> iova_cpuhp_dead(). In the latter case, the solution is "don't do
> that".
> 
> This change should not be necessary.
> 
> Thanks,
> Robin.

Hi Robin,

You are right, kernel 5.15 already has this patch, but kernel 5.10
not contain.

Thanks,
Yunfei.