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Re: efinet SNP issue affects iscsi boot


From: Michael Chang
Subject: Re: efinet SNP issue affects iscsi boot
Date: Thu, 27 Sep 2018 18:22:47 +0800
User-agent: NeoMutt/20170421 (1.8.2)

On Thu, Sep 20, 2018 at 01:26:47PM -0600, Micah Parrish wrote:
> 
> 
> On 09/20/2018 07:47 AM, address@hidden wrote:
> > On Thu, Sep 20, 2018 at 06:38:07PM +0800, Michael Chang wrote:
> > > On Thu, Sep 13, 2018 at 06:06:15PM -0600, Micah Parrish wrote:
> > > > Hi, new subscriber here.? We have a problem with Grub 2 and its use of 
> > > > SNP
> > > > instead of MNP.? Our UEFI driver for a network card parses the relevant 
> > > > DHCP
> > > > options for iSCSI boot, generates an iBFT table, then gets closed by 
> > > > Grub
> > > > when it opens the SNP interface. The driver removes the iBFT table as 
> > > > part
> > > > of normal unload cleanup.? I think this should happen with the Tianocore
> > > > UEFI reference driver as well.? The problem is often masked or does not
> > > > occur when there are multiple network ports enabled.? It occurs with 
> > > > several
> > > > different vendors NICs.
> > > > 
> > > > Possible solutions I see:
> > > > 
> > > > 1. Grub parses the DHCP options and creates its own iBFT.
> > > > 
> > > > 2. Grub copies the already generated iBFT before destroying the 
> > > > interface.
> > > > 
> > > > 3. Grub opens the network interface MNP instead of SNP.
> > > > 
> > > > Although I am a neophyte at grub and UEFI development, I would like to 
> > > > start
> > > > a discussion on possible solutions.? Has anyone else seen this?
> > > For possible solution 3, I managed to work out patch to use MNP but is not
> > > polished, although it survived my testing. If you don't mind and willing 
> > > to
> > > give it go I will post it here as RFC patch for review.
> > That would be perfect. However, there are a few things worth mentioning 
> > here.
> > 
> > The issue is never ending story. So, please look for relevant discussions
> > in grub-devel archives and take them into account if it is possible/make 
> > sense.
> > If you have any difficulties with finding them drop me a line.
> > 
> > Please do not drop SNP driver. I think that we should make MNP driver a new
> > default and SNP should stay as a backup. Just in case.
> > 
> > Additionally, a few days ago I have started looking for people interested
> > in the project. There are some. Hence, if you are going to take a stab at
> > it I will ask them to do some reviews of your work. I will drop you their
> > emails if they are happy to do so.
> 
> Thank you for the context.  I read through the archives, searching for SNP. 
> I'm willing to test whatever we come up with.

I have posted the RFC patch to the list. If you don't see it please let me know.

> I also read through the efinet.c from OpenSolaris.  It is quite different
> from the current SNP efinet.c, since it uses a ring buffer and filters.  I
> assume a naive switch over to MNP might run into the same lost packet
> problem seen before.  Was it seen across many platforms, or specific to a
> few?

I did not experience any packet loss problem. But neverthelast I would like to
have a look on the OpenSolaris patch. Where can I find it ?

Thanks,
Michael

> 
> -Micah
> 
> 

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