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

Alok Kataria
2009-09-29T17:25:22Z

On Tue, 2009-09-29 at 02:01 -0700, Chris Wright wrote:
> * Alok Kataria (akataria@vmware.com) wrote:
> >
> > 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.
>
> Looks good to me (missing Signed-off-by). I think it's also useful
> to generate some runtime noise saying it's a deprecated option.
>
> Even something as simple as:
>
> - pv_info.name = "vmi"
> + pv_info.name = "vmi [deprecated]";
>

Yep, I was thinking of adding KERN_WARN's in vmi_init, though I like
your suggestion better. Also added SOB line. Thanks.

--

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

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

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

Signed-off-by: Alok N Kataria <akataria@vmware.com>
---

Documentation/feature-removal-schedule.txt | 30 ++++++++++++++++++++++++++++
arch/x86/Kconfig | 12 ++++++++---
arch/x86/kernel/vmi_32.c | 2 +-
3 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 89a47b5..04e6c81 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@kernel.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@vmware.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"
diff --git a/arch/x86/kernel/vmi_32.c b/arch/x86/kernel/vmi_32.c
index 31e6f6c..d430e4c 100644
--- a/arch/x86/kernel/vmi_32.c
+++ b/arch/x86/kernel/vmi_32.c
@@ -648,7 +648,7 @@ static inline int __init activate_vmi(void)

pv_info.paravirt_enabled = 1;
pv_info.kernel_rpl = kernel_cs & SEGMENT_RPL_MASK;
- pv_info.name = "vmi";
+ pv_info.name = "vmi [deprecated]";

pv_init_ops.patch = vmi_patch;