netdev - Re: [PATCH 04/13] HV: Mark vmbus ring buffer visible to host in Isolation VM

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Date:   Mon, 2 Aug 2021 20:56:29 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
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Subject: Re: [PATCH 04/13] HV: Mark vmbus ring buffer visible to host in
 Isolation VM



On 8/2/2021 8:07 PM, Joerg Roedel wrote:
> On Wed, Jul 28, 2021 at 10:52:19AM -0400, Tianyu Lan wrote:
>> +	if (type == HV_GPADL_BUFFER)
>> +		index = 0;
>> +	else
>> +		index = channel->gpadl_range[1].gpadlhandle ? 2 : 1;
> 
> Hmm... This doesn't look very robust. Can you set fixed indexes for
> different buffer types? HV_GPADL_BUFFER already has fixed index 0. But
> as it is implemented here you risk that index 2 gets overwritten by
> subsequent calls.

Both second and third are HV_GPADL_RING type. One is send ring and the
other is receive ring. The driver keeps the order to allocate rx and
tx buffer. You are right this is not robust and will add a mutex to keep
the order.