From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124])
 by mx.groups.io with SMTP id smtpd.web09.4279.1654158914713208785
 for <devel@edk2.groups.io>;
 Thu, 02 Jun 2022 01:35:15 -0700
Authentication-Results: mx.groups.io;
 dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=DO0UGz8T;
 spf=pass (domain: redhat.com, ip: 170.10.133.124, mailfrom: kraxel@redhat.com)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;
	s=mimecast20190719; t=1654158913;
	h=from:from:reply-to:subject:subject:date:date:message-id:message-id:
	 to:to:cc:cc:mime-version:mime-version:content-type:content-type:
	 in-reply-to:in-reply-to:references:references;
	bh=/78xyAJrsu0yWPcTRm8wSJGVZxHgbA9zMC4Q9uS+RYs=;
	b=DO0UGz8TaFYJ8WESmDmM/RBDNB0WJlR4VStNU2c3YesqboIyTeJlG+Lfp7NX/pFs0xyOL2
	OHEjNNisfkesjIiitV0xAga9UwDTbRoUxsR0ObuaawkTyMhhvtLz6GwBMDlv8PQ1pyISHA
	0OCHwQyF4CDg++9kG2j/y4CLKjGjwiU=
Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com
 [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS
 (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id
 us-mta-356-U1qL-2EaPpO6WeeYNmDBeQ-1; Thu, 02 Jun 2022 04:35:07 -0400
X-MC-Unique: U1qL-2EaPpO6WeeYNmDBeQ-1
Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2])
	(using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
	(No client certificate requested)
	by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 317431C16B48;
	Thu,  2 Jun 2022 08:35:07 +0000 (UTC)
Received: from sirius.home.kraxel.org (unknown [10.39.194.92])
	by smtp.corp.redhat.com (Postfix) with ESMTPS id 01E8F40EC005;
	Thu,  2 Jun 2022 08:35:06 +0000 (UTC)
Received: by sirius.home.kraxel.org (Postfix, from userid 1000)
	id 5001618000B2; Thu,  2 Jun 2022 10:35:05 +0200 (CEST)
Date: Thu, 2 Jun 2022 10:35:05 +0200
From: "Gerd Hoffmann" <kraxel@redhat.com>
To: Benjamin Doron <benjamin.doron00@gmail.com>
Cc: devel@edk2.groups.io
Subject: Re: [edk2-devel] [PATCH 00/12] Introduce Bootlog DEBUG() output
Message-ID: <20220602083505.dfyb5pmchbe5rgkp@sirius.home.kraxel.org>
References: <20220601093352.hx4w447n7myc7re6@sirius.home.kraxel.org>
 <30076.1654102720972535874@groups.io>
MIME-Version: 1.0
In-Reply-To: <30076.1654102720972535874@groups.io>
X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2
Authentication-Results: relay.mimecast.com;
	auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kraxel@redhat.com
X-Mimecast-Spam-Score: 0
X-Mimecast-Originator: redhat.com
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline

  Hi,

> > Hmm. Maybe it's time to tackle the log performance problem for virtual
> > machines? Create a debug log device with DMA support, so we don't need
> > a vmexit for every single character we want log?
> 
> Of course, that doesn't work for native systems.

Yep.  Maybe we should have both ;)

> > How does that relate to coreboot? coreboot has logging-to-memory too.
> > Not sure what the state is, there have been discussions on the coreboot
> > list about changing that from a pure text log to something structed with
> > timestamps a while back. Don't know whenever this did actually happen.
> > 
> > So, when adding logging-to-memory to edk2 it surely make sense to
> > coordinate that with coreboot, so we'll have both coreboot and edk2 logs
> > there in case edk2 runs as coreboot payload.
> 
> I'm working on getting a SerialPortLib that logs to CBMEM merged. It's on the list at the moment.

> Some comments on DebugLibBootlog:

> - SMM-phase logging can be implemented, but I'm not convinced that sharing DXE's buffer is entirely safe. Using SMM communicate could be safer, but would be more complicated. I stopped working on it when the return-on-investment was too low.

DebugLibBootlog supports multiple buffers.  So we could have one for
coreboot, one for edk2 pei/dxe, one for edk2 smm, one for shim, one for
grub, ...

take care,
  Gerd