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

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Date:	Tue, 22 Sep 2009 12:30:45 -0700
From:	Alok Kataria <akataria@...are.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	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].

Hi Ingo,

On Sun, 2009-09-20 at 00:42 -0700, Ingo Molnar wrote:

> 
> The thing is, the overwhelming majority of vmware users dont benefit 
> from hardware features like nested page tables yet. So this needs to be 
> done _way_ more carefully, with a proper sunset period of a couple of 
> kernel cycles.

I am fine with that too. Below is a patch which adds notes in
feature-removal-schedule.txt, I have marked it for removal from 2.6.34.
Please consider this patch for 2.6.32.

> If we were able to rip out all (or most) of paravirt from arch/x86 it 
> would be tempting for other technical reasons - but the patch above is 
> well localized.

We can certainly look at removing some paravirt-hooks which are only
used by VMI. Not sure if there are any but will take a look when we
actually remove VMI.

Thanks,
Alok

--

Mark VMI for deprecation 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.
Patch on top of tip/master.

Details about VMware's plan about retiring VMI  can be found here
http://blogs.vmware.com/guestosguide/2009/09/vmi-retirement.html

---

 Documentation/feature-removal-schedule.txt |   24 ++++++++++++++++++++++++
 arch/x86/Kconfig                           |    8 +++++---
 2 files changed, 29 insertions(+), 3 deletions(-)


diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index fa75220..b985328 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -459,3 +459,27 @@ 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:	2.6.34
+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 paravirtulization 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, in a couple of releases.
+	Please note that VMI has always been an optimization and non-VMI kernels
+	still work fine on VMware's platform.
+
+	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 e214f45..1f3e156 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -485,14 +485,16 @@ if PARAVIRT_GUEST
 source "arch/x86/xen/Kconfig"
 
 config VMI
-	bool "VMI Guest support"
-	select PARAVIRT
-	depends on X86_32
+	bool "VMI Guest support [will be deprecated soon]"
+	default n
+	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.
+	  VMware has started a phased retirement of this feature from there
+	  products. Please see feature-removal-schedule.txt for details.
 
 config KVM_CLOCK
 	bool "KVM paravirtualized clock"


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