[PATCH net 1/3] hv_netvsc: Correct the max receive buffer size

[Haiyang Zhang]

> -----Original Message-----
> From: Dan Carpenter [mailto:dan.carpenter at oracle.com]
> Sent: Friday, December 8, 2017 5:33 AM
> To: Stephen Hemminger <stephen at networkplumber.org>
> Cc: KY Srinivasan <kys at microsoft.com>; Haiyang Zhang
> <haiyangz at microsoft.com>; Stephen Hemminger
> <sthemmin at microsoft.com>; devel at linuxdriverproject.org;
> netdev at vger.kernel.org
> Subject: Re: [PATCH net 1/3] hv_netvsc: Correct the max receive buffer size
> 
> On Thu, Dec 07, 2017 at 04:10:53PM -0800, Stephen Hemminger wrote:
> > From: Haiyang Zhang <haiyangz at microsoft.com>
> >
> > It should be 31 MB on recent host versions.
> >
> > Signed-off-by: Haiyang Zhang <haiyangz at microsoft.com>
> > Signed-off-by: Stephen Hemminger <sthemmin at microsoft.com>
> 
> This is very vague.  What does "recent" mean in this context?  There are also
> some unrelated white space changes here which make the patch harder to
> read.
> 
> This patch kind of makes the bug fixed by patch 2 even worse because
> before the receive buffer was capped at around 16MB and now we can set
> the receive buffer to 31MB.  It might make sense to fold the two patches
> together.
> 
> Is patch 2 a memory corruption bug?  The changelog doesn't really say what
> the user visible effects of the bug are.  Basically if you make the buffer too
> small then it's a performance issue but if you make it too large what happens?
> It's not clear to me.

For NVSP v2, and earlier host, the limit is 15MB. Later hosts, the limit is 31MB.
Setting beyond it will be denied by the host, resulting the vNIC doesn't come up.

I will merge this one together with the patch 2.

Thanks,
- Haiyang