linux-kernel - Re: [PATCH V3] swiotlb: Split up single swiotlb lock

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Message-ID: <fdcf093c-4a42-ddb7-abc6-c595cb92763e@gmail.com>
Date:   Sat, 9 Jul 2022 00:21:44 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     corbet@....net, m.szyprowski@...sung.com, robin.murphy@....com,
        paulmck@...nel.org, bp@...e.de, akpm@...ux-foundation.org,
        keescook@...omium.org, pmladek@...e.com, rdunlap@...radead.org,
        damien.lemoal@...nsource.wdc.com, michael.h.kelley@...rosoft.com,
        kys@...rosoft.com, Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        iommu@...ts.linux-foundation.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, vkuznets@...hat.com,
        wei.liu@...nel.org, parri.andrea@...il.com,
        thomas.lendacky@....com, linux-hyperv@...r.kernel.org,
        kirill.shutemov@...el.com, andi.kleen@...el.com,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH V3] swiotlb: Split up single swiotlb lock

On 7/8/2022 1:07 AM, Christoph Hellwig wrote:
> Thanks, this looks much better.  I think there is a small problem
> with how default_nareas is set - we need to use 0 as the default
> so that an explicit command line value of 1 works.  Als have you
> checked the interaction with swiotlb_adjust_size in detail?

Yes, the patch was tested in the Hyper-V SEV VM which always calls
swiotlb_adjust_size() to adjust bounce buffer size according to memory
size. It will round up bounce buffer size to the next power of 2 if the 
memory size is not power of 2.