linux-kernel - Re: [PATCH 2/2] x86/ACPI: Set swiotlb area according to the number of lapic entry in MADT

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Message-ID: <a876f862-c005-108d-e6f9-68336a8d89f0@gmail.com>
Date:   Fri, 1 Jul 2022 01:02:21 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     corbet@....net, rafael@...nel.org, len.brown@...el.com,
        pavel@....cz, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        m.szyprowski@...sung.com, robin.murphy@....com, paulmck@...nel.org,
        akpm@...ux-foundation.org, keescook@...omium.org,
        songmuchun@...edance.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, linux-pm@...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 2/2] x86/ACPI: Set swiotlb area according to the number of
 lapic entry in MADT

On 6/29/2022 10:04 PM, Christoph Hellwig wrote:
> On Mon, Jun 27, 2022 at 11:31:50AM -0400, Tianyu Lan wrote:
>> From: Tianyu Lan <Tianyu.Lan@...rosoft.com>
>>
>> When initialize swiotlb bounce buffer, smp_init() has not been
>> called and cpu number can not be got from num_online_cpus().
>> Use the number of lapic entry to set swiotlb area number and
>> keep swiotlb area number equal to cpu number on the x86 platform.
> 
> Can we reorder that initialization?  Because I really hate having
> to have an arch hook in every architecture.

How about using "flags" parameter of swiotlb_init() to pass area number
or add new parameter for area number?

I just reposted patch 1 since there is just some coding style issue and 
area number may also set via swiotlb kernel parameter. We still need 
figure out a good solution to pass area number from architecture code.