linux-kernel - Re: Paravirtualization on VMware's Platform [VMI].

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Message-Id: <1254193238.13456.48.camel@ank32.eng.vmware.com>
Date:	Mon, 28 Sep 2009 20:00:38 -0700
From:	Alok Kataria <akataria@...are.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Gerd Hoffmann <kraxel@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"virtualization@...ts.osdl.org" <virtualization@...ts.osdl.org>,
	Greg KH <greg@...ah.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Paravirtualization on VMware's Platform [VMI].


On Mon, 2009-09-28 at 19:25 -0700, H. Peter Anvin wrote:
> On 09/28/2009 05:45 PM, Alok Kataria wrote:
> > +	bool "VMI Guest support [will be deprecated soon]"
> > +	default n
> 
> This is incorrect use of the word "deprecated"... it's *already*
> deprecated (a word which pretty much means the opposite of "recommended".)
> 
> As far as "default n" is concerned... this is usually not necessary; "n"
> is the default unless anything else is specified.

How about this ?  Thanks.

--
Mark VMI for removal in feature-removal-schedule.txt.

From: Alok N Kataria <akataria@...are.com>

Add text in feature-removal.txt and also modify Kconfig to disable
vmi by default.

---

 Documentation/feature-removal-schedule.txt |   30 ++++++++++++++++++++++++++++
 arch/x86/Kconfig                           |   12 ++++++++---
 2 files changed, 39 insertions(+), 3 deletions(-)


diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 89a47b5..d24c1af 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -451,3 +451,33 @@ Why:	OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR
 	will also allow making ALSA OSS emulation independent of
 	sound_core.  The dependency will be broken then too.
 Who:	Tejun Heo <tj@...nel.org>
+
+----------------------------
+
+What:	Support for VMware's guest paravirtuliazation technique [VMI] will be
+	dropped.
+When:	2.6.37 or earlier.
+Why:	With the recent innovations in CPU hardware acceleration technologies
+	from Intel and AMD, VMware ran a few experiments to compare these
+	techniques to guest paravirtualization technique on VMware's platform.
+	These hardware assisted virtualization techniques have outperformed the
+	performance benefits provided by VMI in most of the workloads. VMware
+	expects that these hardware features will be ubiquitous in a couple of
+	years, as a result, VMware has started a phased retirement of this
+	feature from the hypervisor. We will be removing this feature from the
+	Kernel too. Right now we are targeting 2.6.37 but can retire earlier if
+	technical reasons ( read opportunity to remove major chunk of pvops)
+	arise.
+
+	Please note that VMI has always been an optimization and non-VMI kernels
+	still work fine on VMware's platform.
+	Latest versions of VMware's product which support VMI are,
+	Workstation 7.0 and VSphere 4.0 on ESX side, future maintainence
+	releases for these products will continue supporting VMI.
+
+	For more details about VMI retirement take a look at this,
+	http://blogs.vmware.com/guestosguide/2009/09/vmi-retirement.html
+
+Who:	Alok N Kataria <akataria@...are.com>
+
+----------------------------
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f777aaf..44c1660 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -496,14 +496,20 @@ if PARAVIRT_GUEST
 source "arch/x86/xen/Kconfig"
 
 config VMI
-	bool "VMI Guest support"
-	select PARAVIRT
-	depends on X86_32
+	bool "VMI Guest support [deprecated]"
+	depends on X86_32 && PARAVIRT
 	---help---
 	  VMI provides a paravirtualized interface to the VMware ESX server
 	  (it could be used by other hypervisors in theory too, but is not
 	  at the moment), by linking the kernel to a GPL-ed ROM module
 	  provided by the hypervisor.
+	  As of September 2009, VMware has started a phased retirement of this
+	  feature from VMware's products. Please see
+	  feature-removal-schedule.txt for details.
+	  If you are planning to enable this option, please note that you
+	  cannot live migrate a VMI enabled VM to a future VMware product,
+	  which doesn't support VMI. So if you expect your kernel to seamlessly
+	  migrate to newer VMware products, keep this disabled.
 
 config KVM_CLOCK
 	bool "KVM paravirtualized clock"



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