linux-kernel - Re: [PATCH 3/5] hyperv/IOMMU: Enable swiotlb bounce buffer for Isolation VM

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Message-ID: <c93bf3d4-75c1-bc3d-2789-1d65e7c19158@gmail.com>
Date:   Wed, 17 Nov 2021 22:00:08 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Christoph Hellwig <hch@....de>
Cc:     dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        hpa@...or.com, jgross@...e.com, sstabellini@...nel.org,
        boris.ostrovsky@...cle.com, kys@...rosoft.com,
        haiyangz@...rosoft.com, sthemmin@...rosoft.com, wei.liu@...nel.org,
        decui@...rosoft.com, joro@...tes.org, will@...nel.org,
        davem@...emloft.net, kuba@...nel.org, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, m.szyprowski@...sung.com,
        robin.murphy@....com, xen-devel@...ts.xenproject.org,
        michael.h.kelley@...rosoft.com,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        iommu@...ts.linux-foundation.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        netdev@...r.kernel.org, vkuznets@...hat.com, brijesh.singh@....com,
        konrad.wilk@...cle.com, parri.andrea@...il.com,
        thomas.lendacky@....com, dave.hansen@...el.com
Subject: Re: [PATCH 3/5] hyperv/IOMMU: Enable swiotlb bounce buffer for
 Isolation VM

On 11/17/2021 6:01 PM, Christoph Hellwig wrote:
> This doesn't really have much to do with normal DMA mapping,
> so why does this direct through the dma ops?
> 

According to the previous discussion, dma_alloc_noncontigous()
and dma_vmap_noncontiguous() may be used to handle the noncontigous
memory alloc/map in the netvsc driver. So add alloc/free and vmap/vunmap
callbacks here to handle the case. The previous patch v4 & v5 handles
the allocation and map in the netvsc driver. If this should not go 
though dma ops, We also may make it as vmbus specific function and keep
the function in the vmbus driver.

https://lkml.org/lkml/2021/9/28/51