linux-kernel - Re: [PATCH v11 01/12] iova: Export alloc_iova_fast() and free_iova_fast()

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Message-ID: <5f4eadda-5500-9bac-4368-48cfca6d0a4d@huawei.com>
Date:   Wed, 25 Aug 2021 11:39:22 +0100
From:   John Garry <john.garry@...wei.com>
To:     Will Deacon <will@...nel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>
CC:     <kvm@...r.kernel.org>, <jasowang@...hat.com>,
        <virtualization@...ts.linux-foundation.org>,
        <christian.brauner@...onical.com>, <corbet@....net>,
        <willy@...radead.org>, <hch@...radead.org>,
        Xie Yongji <xieyongji@...edance.com>,
        <dan.carpenter@...cle.com>, <sgarzare@...hat.com>,
        <xiaodong.liu@...el.com>, <linux-fsdevel@...r.kernel.org>,
        <viro@...iv.linux.org.uk>, <stefanha@...hat.com>,
        <songmuchun@...edance.com>, <axboe@...nel.dk>,
        <zhe.he@...driver.com>, <gregkh@...uxfoundation.org>,
        <rdunlap@...radead.org>, <linux-kernel@...r.kernel.org>,
        <iommu@...ts.linux-foundation.org>, <bcrl@...ck.org>,
        <netdev@...r.kernel.org>, <joe@...ches.com>,
        <robin.murphy@....com>, <mika.penttila@...tfour.com>
Subject: Re: [PATCH v11 01/12] iova: Export alloc_iova_fast() and
 free_iova_fast()

On 25/08/2021 10:55, Will Deacon wrote:
> On Tue, Aug 24, 2021 at 02:08:33PM -0400, Michael S. Tsirkin wrote:
>> On Wed, Aug 18, 2021 at 08:06:31PM +0800, Xie Yongji wrote:
>>> Export alloc_iova_fast() and free_iova_fast() so that
>>> some modules can make use of the per-CPU cache to get
>>> rid of rbtree spinlock in alloc_iova() and free_iova()
>>> during IOVA allocation.
>>>
>>> Signed-off-by: Xie Yongji <xieyongji@...edance.com>
>>
>>
>> This needs ack from iommu maintainers. Guys?
> 
> Looks fine to me:
> 
> Acked-by: Will Deacon <will@...nel.org>
> 
> Will
> _______________________________________________
> iommu mailing list
> iommu@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
> .
> 

JFYI, There was a preliminary discussion to move the iova rcache code 
(which the iova fast alloc and free functions are based on) out of the 
iova code and maybe into dma-iommu (being the only user). There was 
other motivation.

https://lore.kernel.org/linux-iommu/83de3911-145d-77c8-17c1-981e4ff825d3@arm.com/

Having more users complicates that...

Thanks,
John

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