[PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Yan Li]

Since the mtrr empty was detected very early before we can use DMI or
PCI to check whether we are running as a VMware guest or not, we now
only print an info there. Warning will only be issued later when we
are sure that we are not running as a VMware guest.

mtrr_trim_uncached_memory() is modified to return meaningful codes for
later warning decision.

Signed-off-by: Yan Li <elliot.li.tech@gmail.com>
---
 arch/x86/kernel/cpu/mtrr/main.c |   16 +++++++++++++++-
 arch/x86/kernel/setup.c         |   27 ++++++++++++++++++++++++++-
 include/asm-x86/mtrr.h          |    2 ++
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index b117d7f..95d1cc0 100644
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -1453,6 +1453,11 @@ static u64 __init real_trim_memory(unsigned long start_pfn,
  * all of the memory the kernel is intending to use. If not, it'll trim any
  * memory off the end by adjusting end_pfn, removing it from the kernel's
  * allocation pools, warning the user with an obnoxious message.
+ *
+ * Return code:
+ * EMTRR_ALL_BLANK (-1):  not trimmed due to CPU MTRRs all blank
+ *                    0:  not trimmed due to other reasons
+ *                    1:  trimmed successfully
  */
 int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
 {
@@ -1494,11 +1499,20 @@ int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
 			highest_pfn = base + size;
 	}
 
-	/* kvm/qemu doesn't have mtrr set right, don't trim them all */
+	/* kvm/qemu/VMware doesn't have mtrr set right, don't trim them all */
 	if (!highest_pfn) {
+#ifdef CONFIG_VMWARE_GUEST_DETECT
+		/* the "mtrr all blank" warning will be deferred until
+		 * after DMI scanning and we know the machine is not a
+		 * VMware guest
+		 */
+		printk(KERN_INFO "CPU MTRRs all blank\n");
+		return EMTRR_ALL_BLANK;
+#else
 		WARN(!kvm_para_available(), KERN_WARNING
 				"WARNING: strange, CPU MTRRs all blank?\n");
 		return 0;
+#endif
 	}
 
 	/* check entries number */
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 9838f25..4cbec10 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -102,6 +102,7 @@
 #include <asm/percpu.h>
 #include <asm/topology.h>
 #include <asm/apicdef.h>
+#include <asm/vmware.h>
 #ifdef CONFIG_X86_64
 #include <asm/numa_64.h>
 #endif
@@ -593,6 +594,13 @@ struct x86_quirks *x86_quirks __initdata = &default_x86_quirks;
 
 void __init setup_arch(char **cmdline_p)
 {
+#ifdef CONFIG_VMWARE_GUEST_DETECT
+	/* the "mtrr all blank" warning will be deferred until after
+	 * DMI scanning and we know the machine is not a VMware guest
+	 */
+	int cpu_mtrr_all_blank_later_warning = 0;
+#endif
+
 #ifdef CONFIG_X86_32
 	memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
 	visws_early_detect();
@@ -733,8 +741,16 @@ void __init setup_arch(char **cmdline_p)
 	early_reserve_e820_mpc_new();
 	/* update e820 for memory not covered by WB MTRRs */
 	mtrr_bp_init();
-	if (mtrr_trim_uncached_memory(max_pfn))
+	switch (mtrr_trim_uncached_memory(max_pfn)) {
+	case 1:
 		max_pfn = e820_end_of_ram_pfn();
+		break;
+#ifdef CONFIG_VMWARE_GUEST_DETECT
+	case EMTRR_ALL_BLANK:
+		cpu_mtrr_all_blank_later_warning = 1;
+		break;
+#endif
+	}
 
 #ifdef CONFIG_X86_32
 	/* max_low_pfn get updated here */
@@ -783,6 +799,15 @@ void __init setup_arch(char **cmdline_p)
 
 	dmi_scan_machine();
 
+#ifdef CONFIG_VMWARE_GUEST_DETECT
+	if (cpu_mtrr_all_blank_later_warning) {
+		WARN(!(kvm_para_available() || (is_vmware_guest())),
+		     KERN_WARNING
+		     "WARNING: strange, CPU MTRRs all blank? "
+		     "Deferred from mtrr_trim_uncached_memory()\n");
+	}
+#endif
+
 	io_delay_init();
 
 	/*
diff --git a/include/asm-x86/mtrr.h b/include/asm-x86/mtrr.h
index a69a01a..b6d8fcb 100644
--- a/include/asm-x86/mtrr.h
+++ b/include/asm-x86/mtrr.h
@@ -26,6 +26,8 @@
 #include <linux/ioctl.h>
 #include <linux/errno.h>
 
+#define	EMTRR_ALL_BLANK (-1)
+
 #define	MTRR_IOCTL_BASE	'M'
 
 struct mtrr_sentry {
-- 
1.5.4.3


-- 
Li, Yan

"Everything that is really great and inspiring is created by the
individual who can labor in freedom."
              - Albert Einstein, in Out of My Later Years (1950)

Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Laurent Vivier]

Le mercredi 24 septembre 2008 à 20:24 +0800, Yan Li a écrit :
> Since the mtrr empty was detected very early before we can use DMI or
> PCI to check whether we are running as a VMware guest or not, we now
> only print an info there. Warning will only be issued later when we
> are sure that we are not running as a VMware guest.
> 
> mtrr_trim_uncached_memory() is modified to return meaningful codes for
> later warning decision.
> 
> Signed-off-by: Yan Li <elliot.li.tech@gmail.com>
> ---
>  arch/x86/kernel/cpu/mtrr/main.c |   16 +++++++++++++++-
>  arch/x86/kernel/setup.c         |   27 ++++++++++++++++++++++++++-
>  include/asm-x86/mtrr.h          |    2 ++
>  3 files changed, 43 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
> index b117d7f..95d1cc0 100644
> --- a/arch/x86/kernel/cpu/mtrr/main.c
> +++ b/arch/x86/kernel/cpu/mtrr/main.c
> @@ -1453,6 +1453,11 @@ static u64 __init real_trim_memory(unsigned long start_pfn,
>   * all of the memory the kernel is intending to use. If not, it'll trim any
>   * memory off the end by adjusting end_pfn, removing it from the kernel's
>   * allocation pools, warning the user with an obnoxious message.
> + *
> + * Return code:
> + * EMTRR_ALL_BLANK (-1):  not trimmed due to CPU MTRRs all blank
> + *                    0:  not trimmed due to other reasons
> + *                    1:  trimmed successfully
>   */
>  int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
>  {
> @@ -1494,11 +1499,20 @@ int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
>  			highest_pfn = base + size;
>  	}
>  
> -	/* kvm/qemu doesn't have mtrr set right, don't trim them all */
> +	/* kvm/qemu/VMware doesn't have mtrr set right, don't trim them all */
>  	if (!highest_pfn) {
> +#ifdef CONFIG_VMWARE_GUEST_DETECT
> +		/* the "mtrr all blank" warning will be deferred until
> +		 * after DMI scanning and we know the machine is not a
> +		 * VMware guest
> +		 */
> +		printk(KERN_INFO "CPU MTRRs all blank\n");
> +		return EMTRR_ALL_BLANK;
> +#else
>  		WARN(!kvm_para_available(), KERN_WARNING
>  				"WARNING: strange, CPU MTRRs all blank?\n");
>  		return 0;
> +#endif
>  	}

perhaps something like:

#ifdef CONFIG_VMWARE_GUEST_DETECT
 		WARN(!kvm_para_available() && !is_vmware_guest(), KERN_WARNING
				"WARNING: strange, CPU MTRRs all blank?\n");
#else
 		WARN(!kvm_para_available(), KERN_WARNING
  				"WARNING: strange, CPU MTRRs all blank?\n");
...

???

Laurent
-- 
----------------- Laurent.Vivier@bull.net  ------------------
  "La perfection est atteinte non quand il ne reste rien à
ajouter mais quand il ne reste rien à enlever." Saint Exupéry

Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Yan Li]

On Wed, Sep 24, 2008 at 02:54:14PM +0200, Laurent Vivier wrote:
> Le mercredi 24 septembre 2008 à 20:24 +0800, Yan Li a écrit :
> > +#ifdef CONFIG_VMWARE_GUEST_DETECT
> > +		/* the "mtrr all blank" warning will be deferred until
> > +		 * after DMI scanning and we know the machine is not a
> > +		 * VMware guest
> > +		 */
> > +		printk(KERN_INFO "CPU MTRRs all blank\n");
> > +		return EMTRR_ALL_BLANK;
> > +#else
> >  		WARN(!kvm_para_available(), KERN_WARNING
> >  				"WARNING: strange, CPU MTRRs all blank?\n");
> >  		return 0;
> > +#endif
> >  	}
> 
> perhaps something like:
> 
> #ifdef CONFIG_VMWARE_GUEST_DETECT
>  		WARN(!kvm_para_available() && !is_vmware_guest(), KERN_WARNING
> 				"WARNING: strange, CPU MTRRs all blank?\n");
> #else
>  		WARN(!kvm_para_available(), KERN_WARNING
>   				"WARNING: strange, CPU MTRRs all blank?\n");
> ...
> 
> ???

As stated in the comments: the warning has to be deferred. The reason
is that "is_vmware_guest()" replies on DMI and can only be used after
dmi_scan().  These mtrr codes here are run very early during
setup_arch() when the DMI is not available. So when I've detected all
MTRRs are blank, I returned a status code to setup_arch(), who will
call "is_vmware_guest()" later, after dmi_scan(), to decide whether to
issue a warning or not.


-- 
Li, Yan

"Everything that is really great and inspiring is created by the
individual who can labor in freedom."
              - Albert Einstein, in Out of My Later Years (1950)

Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Joerg Roedel]

On Wed, Sep 24, 2008 at 08:24:37PM +0800, Yan Li wrote:
> Since the mtrr empty was detected very early before we can use DMI or
> PCI to check whether we are running as a VMware guest or not, we now
> only print an info there. Warning will only be issued later when we
> are sure that we are not running as a VMware guest.
> 
> mtrr_trim_uncached_memory() is modified to return meaningful codes for
> later warning decision.

A lot of code if #ifdef'ed to vmware. Can you hide this into a header
file? This way its not very clean code I think.

> Signed-off-by: Yan Li <elliot.li.tech@gmail.com>
> ---
>  arch/x86/kernel/cpu/mtrr/main.c |   16 +++++++++++++++-
>  arch/x86/kernel/setup.c         |   27 ++++++++++++++++++++++++++-
>  include/asm-x86/mtrr.h          |    2 ++
>  3 files changed, 43 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
> index b117d7f..95d1cc0 100644
> --- a/arch/x86/kernel/cpu/mtrr/main.c
> +++ b/arch/x86/kernel/cpu/mtrr/main.c
> @@ -1453,6 +1453,11 @@ static u64 __init real_trim_memory(unsigned long start_pfn,
>   * all of the memory the kernel is intending to use. If not, it'll trim any
>   * memory off the end by adjusting end_pfn, removing it from the kernel's
>   * allocation pools, warning the user with an obnoxious message.
> + *
> + * Return code:
> + * EMTRR_ALL_BLANK (-1):  not trimmed due to CPU MTRRs all blank
> + *                    0:  not trimmed due to other reasons
> + *                    1:  trimmed successfully
>   */
>  int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
>  {
> @@ -1494,11 +1499,20 @@ int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
>  			highest_pfn = base + size;
>  	}
>  
> -	/* kvm/qemu doesn't have mtrr set right, don't trim them all */
> +	/* kvm/qemu/VMware doesn't have mtrr set right, don't trim them all */
>  	if (!highest_pfn) {
> +#ifdef CONFIG_VMWARE_GUEST_DETECT
> +		/* the "mtrr all blank" warning will be deferred until
> +		 * after DMI scanning and we know the machine is not a
> +		 * VMware guest
> +		 */
> +		printk(KERN_INFO "CPU MTRRs all blank\n");
> +		return EMTRR_ALL_BLANK;
> +#else
>  		WARN(!kvm_para_available(), KERN_WARNING
>  				"WARNING: strange, CPU MTRRs all blank?\n");
>  		return 0;
> +#endif

Can we move the WARN after the DMI scanning for all cases? This will
save this #ifdef and is a cleaner approach imho.

>  	}
>  
>  	/* check entries number */
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 9838f25..4cbec10 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -102,6 +102,7 @@
>  #include <asm/percpu.h>
>  #include <asm/topology.h>
>  #include <asm/apicdef.h>
> +#include <asm/vmware.h>
>  #ifdef CONFIG_X86_64
>  #include <asm/numa_64.h>
>  #endif
> @@ -593,6 +594,13 @@ struct x86_quirks *x86_quirks __initdata = &default_x86_quirks;
>  
>  void __init setup_arch(char **cmdline_p)
>  {
> +#ifdef CONFIG_VMWARE_GUEST_DETECT
> +	/* the "mtrr all blank" warning will be deferred until after
> +	 * DMI scanning and we know the machine is not a VMware guest
> +	 */
> +	int cpu_mtrr_all_blank_later_warning = 0;
> +#endif
> +
>  #ifdef CONFIG_X86_32
>  	memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
>  	visws_early_detect();
> @@ -733,8 +741,16 @@ void __init setup_arch(char **cmdline_p)
>  	early_reserve_e820_mpc_new();
>  	/* update e820 for memory not covered by WB MTRRs */
>  	mtrr_bp_init();
> -	if (mtrr_trim_uncached_memory(max_pfn))
> +	switch (mtrr_trim_uncached_memory(max_pfn)) {
> +	case 1:
>  		max_pfn = e820_end_of_ram_pfn();
> +		break;
> +#ifdef CONFIG_VMWARE_GUEST_DETECT
> +	case EMTRR_ALL_BLANK:
> +		cpu_mtrr_all_blank_later_warning = 1;
> +		break;
> +#endif
> +	}
>  
>  #ifdef CONFIG_X86_32
>  	/* max_low_pfn get updated here */
> @@ -783,6 +799,15 @@ void __init setup_arch(char **cmdline_p)
>  
>  	dmi_scan_machine();
>  
> +#ifdef CONFIG_VMWARE_GUEST_DETECT
> +	if (cpu_mtrr_all_blank_later_warning) {
> +		WARN(!(kvm_para_available() || (is_vmware_guest())),
> +		     KERN_WARNING
> +		     "WARNING: strange, CPU MTRRs all blank? "
> +		     "Deferred from mtrr_trim_uncached_memory()\n");
> +	}
> +#endif
> +
>  	io_delay_init();
>  
>  	/*
> diff --git a/include/asm-x86/mtrr.h b/include/asm-x86/mtrr.h
> index a69a01a..b6d8fcb 100644
> --- a/include/asm-x86/mtrr.h
> +++ b/include/asm-x86/mtrr.h
> @@ -26,6 +26,8 @@
>  #include <linux/ioctl.h>
>  #include <linux/errno.h>
>  
> +#define	EMTRR_ALL_BLANK (-1)
> +
>  #define	MTRR_IOCTL_BASE	'M'
>  
>  struct mtrr_sentry {
> -- 
> 1.5.4.3
> 
> 
> -- 
> Li, Yan
> 
> "Everything that is really great and inspiring is created by the
> individual who can labor in freedom."
>               - Albert Einstein, in Out of My Later Years (1950)
> 

-- 
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 Operating |         Wilschdorfer Landstr. 101, 01109 Dresden, Germany
 System    |                  Register Court Dresden: HRA 4896
 Research  |              General Partner authorized to represent:
 Center    |             AMD Saxony LLC (Wilmington, Delaware, US)
           | General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy

Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Yan Li]

On Wed, Sep 24, 2008 at 04:16:16PM +0200, Joerg Roedel wrote:
> A lot of code if #ifdef'ed to vmware. Can you hide this into a header
> file? This way its not very clean code I think.

Hum.. OK, I'm thinking about this.

> Can we move the WARN after the DMI scanning for all cases? This will
> save this #ifdef and is a cleaner approach imho.

Sounds good. Thanks!


-- 
Li, Yan

Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Yinghai Lu]

On Wed, Sep 24, 2008 at 5:24 AM, Yan Li <elliot.li.tech@gmail.com> wrote:
> Since the mtrr empty was detected very early before we can use DMI or
> PCI to check whether we are running as a VMware guest or not, we now
> only print an info there. Warning will only be issued later when we
> are sure that we are not running as a VMware guest.
>
> mtrr_trim_uncached_memory() is modified to return meaningful codes for
> later warning decision.

we have moved dmi_scan_machine() much early...

so please check with latest tip/master to use
dmi_check_system with that.

BTW:
those warning should be good, because VMware is the root cause.

YH

Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Yan Li]

On Wed, Sep 24, 2008 at 09:39:20AM -0700, Yinghai Lu wrote:
> On Wed, Sep 24, 2008 at 5:24 AM, Yan Li <elliot.li.tech@gmail.com> wrote:
> > Since the mtrr empty was detected very early before we can use DMI or
> > PCI to check whether we are running as a VMware guest or not, we now
> > only print an info there. Warning will only be issued later when we
> > are sure that we are not running as a VMware guest.
> >
> > mtrr_trim_uncached_memory() is modified to return meaningful codes for
> > later warning decision.
> 
> we have moved dmi_scan_machine() much early...
> 
> so please check with latest tip/master to use
> dmi_check_system with that.

OK! Thanks, I'll try.

> BTW:
> those warning should be good, because VMware is the root cause.

Sorry, do you mean we also need a warning for this in VMware?

-- 
Li, Yan

Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Yan Li]

On Wed, Sep 24, 2008 at 09:39:20AM -0700, Yinghai Lu wrote:
> On Wed, Sep 24, 2008 at 5:24 AM, Yan Li <elliot.li.tech@gmail.com> wrote:
> > Since the mtrr empty was detected very early before we can use DMI or
> > PCI to check whether we are running as a VMware guest or not, we now
> > only print an info there. Warning will only be issued later when we
> > are sure that we are not running as a VMware guest.
> >
> > mtrr_trim_uncached_memory() is modified to return meaningful codes for
> > later warning decision.
> 
> we have moved dmi_scan_machine() much early...
> 
> so please check with latest tip/master to use
> dmi_check_system with that.

I checked your patch 1c6e5503 that moved dmi_scan_machine() earlier,
but it's still behind mtrr_trim_uncached_memory(), so we still can't
use DMI to check for VMware there.

-- 
Li, Yan

Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Yinghai Lu]

On Thu, Sep 25, 2008 at 7:18 AM, Yan Li <elliot.li.tech@gmail.com> wrote:
> On Wed, Sep 24, 2008 at 09:39:20AM -0700, Yinghai Lu wrote:
>> On Wed, Sep 24, 2008 at 5:24 AM, Yan Li <elliot.li.tech@gmail.com> wrote:
>> > Since the mtrr empty was detected very early before we can use DMI or
>> > PCI to check whether we are running as a VMware guest or not, we now
>> > only print an info there. Warning will only be issued later when we
>> > are sure that we are not running as a VMware guest.
>> >
>> > mtrr_trim_uncached_memory() is modified to return meaningful codes for
>> > later warning decision.
>>
>> we have moved dmi_scan_machine() much early...
>>
>> so please check with latest tip/master to use
>> dmi_check_system with that.
>
> I checked your patch 1c6e5503 that moved dmi_scan_machine() earlier,
> but it's still behind mtrr_trim_uncached_memory(), so we still can't
> use DMI to check for VMware there.
>

you must be kidding!

...

        dmi_scan_machine();

        dmi_check_system(bad_bios_dmi_table);

#ifdef CONFIG_X86_32
        probe_roms();
#endif

        /* after parse_early_param, so could debug it */
        insert_resource(&iomem_resource, &code_resource);
        insert_resource(&iomem_resource, &data_resource);
        insert_resource(&iomem_resource, &bss_resource);

        if (efi_enabled)
                efi_init();

#ifdef CONFIG_X86_32
        if (ppro_with_ram_bug()) {
                e820_update_range(0x70000000ULL, 0x40000ULL, E820_RAM,
                                  E820_RESERVED);
                sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
                printk(KERN_INFO "fixed physical RAM map:\n");
                e820_print_map("bad_ppro");
        }
#else
        early_gart_iommu_check();
#endif

        /*
         * partially used pages are not usable - thus
         * we are rounding upwards:
         */
        max_pfn = e820_end_of_ram_pfn();

        /* preallocate 4k for mptable mpc */
        early_reserve_e820_mpc_new();
        /* update e820 for memory not covered by WB MTRRs */
        mtrr_bp_init();
        if (mtrr_trim_uncached_memory(max_pfn))
                max_pfn = e820_end_of_ram_pfn();

Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Yan Li]

On Thu, Sep 25, 2008 at 10:13:45AM -0700, Yinghai Lu wrote:
> >> we have moved dmi_scan_machine() much early...
> >>
> >> so please check with latest tip/master to use
> >> dmi_check_system with that.
> >
> > I checked your patch 1c6e5503 that moved dmi_scan_machine() earlier,
> > but it's still behind mtrr_trim_uncached_memory(), so we still can't
> > use DMI to check for VMware there.
> >
> 
> you must be kidding!

Ooops. Sorry, my fault.  I checked the wrong tree. I'm looking into
this.

Thanks!

-- 
Li, Yan

Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Pavel Machek]

Hi!

Subject says: Suppress false "mtrr all empty"  .... would you explain
why is the message false? I believe it is very true, and points out
fact that VMWare virtualization fails to simulate MTRR-s.

IMO VMWare should just fix their emulator.

								Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

[Yan Li]

On Wed, Oct 01, 2008 at 10:03:51PM +0200, Pavel Machek wrote:
> Hi!
> 
> Subject says: Suppress false "mtrr all empty"  .... would you explain
> why is the message false? I believe it is very true, and points out
> fact that VMWare virtualization fails to simulate MTRR-s.
> 
> IMO VMWare should just fix their emulator.

You are right, to some degree. Actually I have no strong evidence to
support this either.  Since KVM doesn't set MTRR, by hunch I thought
VMware might having similar shortages. Also nothing bad can be
observed after the system booted, so I guessed that warning was
useless. Moreover, none other OSes (include old Linux kernels) is
complaining about this in VMware so users of VMware might think 2.6.27
is buggy on this.

Hope someone from VMware could clear this up.  I think they are
working on this problem followed this thread. I'd be happy to help.

-- 
Li, Yan