Re: [PATCH 1/2] kvm tools: set the HYPERVISOR flag in cpuid

[Cyrill Gorcunov <gorcunov@openvz.org>]

On Wed, Jun 20, 2012 at 10:23:06AM +0300, Pekka Enberg wrote:
> On Fri, 15 Jun 2012, Cyrill Gorcunov wrote:
> 
> > On Fri, Jun 15, 2012 at 01:34:16PM +0200, Sasha Levin wrote:
> > > We need to set the HYPERVISOR flag to let the kernel know we're running
> > > under a hypervisor.
> > > 
> > > This makes the kernel enable all sorts of para-virtualization options
> > > such as kvm-clock.
> > > 
> > > Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
> > 
> > OK, looks good, but please Sasha, add a comment into the code
> > itself about the bitflag enabled (or maybe Pekka would add at
> > merge time).
> 
> Sasha?

I think it should be something like below

	Cyrill
---
From: Sasha Levin <levinsasha928@gmail.com>
Subject: [PATCH] kvm tools: set the HYPERVISOR flag in cpuid

We need to set the HYPERVISOR flag to let the kernel know we're running
under a hypervisor.

This makes the kernel enable all sorts of para-virtualization options
such as kvm-clock.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
[gorcunov@: Add comments on bits]
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
 tools/kvm/x86/cpuid.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Index: linux-2.6.git/tools/kvm/x86/cpuid.c
===================================================================
--- linux-2.6.git.orig/tools/kvm/x86/cpuid.c
+++ linux-2.6.git/tools/kvm/x86/cpuid.c
@@ -21,8 +21,13 @@ static void filter_cpuid(struct kvm_cpui
 		struct kvm_cpuid_entry2 *entry = &kvm_cpuid->entries[i];
 
 		switch (entry->function) {
+		case 1:
+			/* Set X86_FEATURE_HYPERVISOR */
+			if (entry->index == 0)
+				entry->ecx |= (1 << 31);
+			break;
 		case 6:
-			/* Clear presence of IA32_ENERGY_PERF_BIAS */
+			/* Clear X86_FEATURE_EPB */
 			entry->ecx = entry->ecx & ~(1 << 3);
 			break;
 		case CPUID_FUNC_PERFMON: