linux-kernel - Re: [PATCH RESEND] netvsc: transfer lower device max tso size

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Message-ID: <CACGkMEtEvkSaYP1s+jq-3RPrX_GAr1gQ+b=b4oytw9_dGnSc_w@mail.gmail.com>
Date: Wed, 23 Jul 2025 14:00:47 +0800
From: Jason Wang <jasowang@...hat.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Cindy Lu <lulu@...hat.com>, "K. Y. Srinivasan" <kys@...rosoft.com>, 
	Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, 
	Dexuan Cui <decui@...rosoft.com>, Andrew Lunn <andrew+netdev@...n.ch>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Michael Kelley <mhklinux@...look.com>, Shradha Gupta <shradhagupta@...ux.microsoft.com>, 
	Kees Cook <kees@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Alexander Lobakin <aleksander.lobakin@...el.com>, Guillaume Nault <gnault@...hat.com>, 
	Joe Damato <jdamato@...tly.com>, Ahmed Zaki <ahmed.zaki@...el.com>, 
	"open list:Hyper-V/Azure CORE AND DRIVERS" <linux-hyperv@...r.kernel.org>, 
	"open list:NETWORKING DRIVERS" <netdev@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND] netvsc: transfer lower device max tso size

On Tue, Jul 22, 2025 at 9:18 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Tue, 22 Jul 2025 09:04:20 +0800 Jason Wang wrote:
> > On Tue, Jul 22, 2025 at 7:28 AM Jakub Kicinski <kuba@...nel.org> wrote:
> > > On Fri, 18 Jul 2025 14:17:55 +0800 Cindy Lu wrote:
> > > > Subject: [PATCH RESEND] netvsc: transfer lower device max tso size
> > >
> > > You say RESEND but I don't see a link to previous posting anywhere.
>
> Someone should respond to this part, please.
>
> > > I'd rather we didn't extend the magic behavior of hyperv/netvsc any
> > > further.
> >
> > Are you referring to the netdev coupling model of the VF acceleration?
>
> Yes, it tries to apply whole bunch of policy automatically in
> the kernel.
>
> > > We have enough problems with it.
> >
> > But this fixes a real problem, otherwise nested VM performance will be
> > broken due to the GSO software segmentation.
>
> Perhaps, possibly, a migration plan can be devised, away from the
> netvsc model, so we don't have to deal with nuggets of joy like:
> https://lore.kernel.org/all/1752870014-28909-1-git-send-email-haiyangz@linux.microsoft.com/

Btw, if I understand this correctly. This is for future development so
it's not a blocker for this patch?

Thanks

>