linux-kernel - Re: [RFC PATCH V2 0/2] swiotlb: Add child io tlb mem support

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Date:   Mon, 9 May 2022 19:49:53 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     hch@...radead.org, robin.murphy@....com
Cc:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        vkuznets@...hat.com, brijesh.singh@....com, konrad.wilk@...cle.com,
        hch@....de, wei.liu@...nel.org, parri.andrea@...il.com,
        thomas.lendacky@....com, linux-hyperv@...r.kernel.org,
        andi.kleen@...el.com, kirill.shutemov@...el.com,
        m.szyprowski@...sung.com, michael.h.kelley@...rosoft.com,
        kys@...rosoft.com
Subject: Re: [RFC PATCH V2 0/2] swiotlb: Add child io tlb mem support

On 5/2/2022 8:54 PM, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> 
> Traditionally swiotlb was not performance critical because it was only
> used for slow devices. But in some setups, like TDX/SEV confidential
> guests, all IO has to go through swiotlb. Currently swiotlb only has a
> single lock. Under high IO load with multiple CPUs this can lead to
> significant lock contention on the swiotlb lock.
> 
> This patch adds child IO TLB mem support to resolve spinlock overhead
> among device's queues. Each device may allocate IO tlb mem and setup
> child IO TLB mem according to queue number. The number child IO tlb
> mem maybe set up equal with device queue number and this helps to resolve
> swiotlb spinlock overhead among devices and queues.
> 
> Patch 2 introduces IO TLB Block concepts and swiotlb_device_allocate()
> API to allocate per-device swiotlb bounce buffer. The new API Accepts
> queue number as the number of child IO TLB mem to set up device's IO
> TLB mem.

Gentile ping...

Thanks.
> 
> Tianyu Lan (2):
>    swiotlb: Add Child IO TLB mem support
>    Swiotlb: Add device bounce buffer allocation interface
> 
>   include/linux/swiotlb.h |  40 ++++++
>   kernel/dma/swiotlb.c    | 290 ++++++++++++++++++++++++++++++++++++++--
>   2 files changed, 317 insertions(+), 13 deletions(-)
>