linux-kernel - Re: [PATCH V4 00/13] x86/Hyper-V: Add Hyper-V Isolation VM support

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Message-ID: <20210902075131.GA14986@lst.de>
Date:   Thu, 2 Sep 2021 09:51:31 +0200
From:   Christoph Hellwig <hch@....de>
To:     Tianyu Lan <ltykernel@...il.com>
Cc:     Christoph Hellwig <hch@....de>, kys@...rosoft.com,
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Subject: Re: [PATCH V4 00/13] x86/Hyper-V: Add Hyper-V Isolation VM support

On Tue, Aug 31, 2021 at 11:20:06PM +0800, Tianyu Lan wrote:
>> If so I suspect the best way to allocate them is by not using vmalloc
>> but just discontiguous pages, and then use kmap_local_pfn where the
>> PFN includes the share_gpa offset when actually copying from/to the
>> skbs.
>>
> When netvsc needs to copy packet data to send buffer, it needs to caculate 
> position with section_index and send_section_size.
> Please seee netvsc_copy_to_send_buf() detail. So the contiguous virtual 
> address of send buffer is necessary to copy data and batch packets.

Actually that makes the kmap approach much easier.  The phys_to_virt
can just be replaced with a kmap_local_pfn and the unmap needs to
be added.  I've been mostly focussing on the receive path, which
would need a similar treatment.