linux-kernel - Re: [PATCH v3 02/10] swiotlb: Factor out slot allocation and free

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Message-ID: <20190423061232.GB12762@lst.de>
Date:   Tue, 23 Apr 2019 08:12:32 +0200
From:   Christoph Hellwig <hch@....de>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Christoph Hellwig <hch@....de>,
        David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>, ashok.raj@...el.com,
        jacob.jun.pan@...el.com, alan.cox@...el.com, kevin.tian@...el.com,
        mika.westerberg@...ux.intel.com, pengfei.xu@...el.com,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 02/10] swiotlb: Factor out slot allocation and free

On Tue, Apr 23, 2019 at 09:58:19AM +0800, Lu Baolu wrote:
> 554         for (i = 0; i < nslots; i++)
> 555                 io_tlb_orig_addr[index+i] = orig_addr + (i << 
> IO_TLB_SHIFT);
>
> Could the tlb orig address set to PAGE_ALIGN_DOWN(orig_addr)? We
> couldn't assume the bounce buffer just starts from the beginning of the
> slot. Or anything I missed?

I don't see why we need to align the orig_addr.  We only use
io_tlb_orig_addr to find the address(es) for the swiotlb_bounce calls,
and I don't see a good reason why we'd need to align those.