[PATCH 0/3] x86/vmware guest improvements

[PATCH 0/3] x86/vmware guest improvements

[Alexey Makhalov]

This patchset includes several VMware guest improvements:

Alexey Makhalov (3):
  x86/vmware: Use tsc_khz value for calibrate_cpu()
  x86/vmware: Add basic paravirt ops support
  x86/vmware: Add paravirt sched clock

 Documentation/kernel-parameters.txt |  4 +++
 arch/x86/kernel/cpu/vmware.c        | 51 +++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)

-- 
2.10.1

[PATCH 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu()

[Alexey Makhalov]

After aa297292d708, there are separate native calibrations for cpu_khz and
tsc_khz. The code sets x86_platform.calibrate_cpu to native_calibrate_cpu()
which looks in cpuid leaf 0x16 or msrs for the cpu frequency. Since we keep
the tsc_khz constant (even after vmotion), the cpu_khz and tsc_khz may
start diverging.

tsc_init() now does

	cpu_khz = x86_platform.calibrate_cpu();
	tsc_khz = x86_platform.calibrate_tsc();
	if (tsc_khz == 0)
		tsc_khz = cpu_khz;
	else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
		cpu_khz = tsc_khz;

We want the cpu_khz and tsc_khz to be sync even if they diverge less then
10%.
This patch resolves this issue by setting x86_platform.calibrate_cpu to
vmware_get_tsc_khz().

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
---
 arch/x86/kernel/cpu/vmware.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 4e34da4b..480790f 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -83,6 +83,7 @@ static void __init vmware_platform_setup(void)
 
 		vmware_tsc_khz = tsc_khz;
 		x86_platform.calibrate_tsc = vmware_get_tsc_khz;
+		x86_platform.calibrate_cpu = vmware_get_tsc_khz;
 
 #ifdef CONFIG_X86_LOCAL_APIC
 		/* Skip lapic calibration since we know the bus frequency. */
-- 
2.10.1

[PATCH 2/3] x86/vmware: Add basic paravirt ops support

[Alexey Makhalov]

Add basic paravirt support:
 1. set pv_info.name to "VMware" to have proper boot log message
	Booting paravirtualized kernel on VMware
    instead of "... on bare hardware"
 2. set pv_cpu_ops.io_delay() to empty function - paravirt_nop() to
    avoid vm-exits on IO delays.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
---
 arch/x86/kernel/cpu/vmware.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 480790f..e3fb320 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -61,6 +61,16 @@ static unsigned long vmware_get_tsc_khz(void)
 	return vmware_tsc_khz;
 }
 
+#ifdef CONFIG_PARAVIRT
+static void __init vmware_paravirt_ops_setup(void)
+{
+	pv_info.name = "VMware";
+	pv_cpu_ops.io_delay = paravirt_nop;
+}
+#else
+#define vmware_paravirt_ops_setup() do {} while (0)
+#endif
+
 static void __init vmware_platform_setup(void)
 {
 	uint32_t eax, ebx, ecx, edx;
@@ -94,6 +104,8 @@ static void __init vmware_platform_setup(void)
 	} else {
 		pr_warn("Failed to get TSC freq from the hypervisor\n");
 	}
+
+	vmware_paravirt_ops_setup();
 }
 
 /*
-- 
2.10.1

Re: [PATCH 2/3] x86/vmware: Add basic paravirt ops support

[Tim Mann]

I believe our trademark guidelines say we aren't supposed to use VMware as a
noun to mean a product, only to mean the company.  So we can say "running on
VMware ESXi" or "running in a VMware virtual machine", but "running on VMware"
is wrong.  There is supposedly some good legal reason for this related to
keeping our trademark.

On Tue, 25 Oct 2016 22:26:00 -0700, Alexey Makhalov <amakhalov@vmware.com>
wrote:
> Add basic paravirt support:
>  1. set pv_info.name to "VMware" to have proper boot log message
> 	Booting paravirtualized kernel on VMware
>     instead of "... on bare hardware"
>  2. set pv_cpu_ops.io_delay() to empty function - paravirt_nop() to
>     avoid vm-exits on IO delays.
> 
> Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
> Acked-by: Alok N Kataria <akataria@vmware.com>
> ---
>  arch/x86/kernel/cpu/vmware.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
> index 480790f..e3fb320 100644
> --- a/arch/x86/kernel/cpu/vmware.c
> +++ b/arch/x86/kernel/cpu/vmware.c
> @@ -61,6 +61,16 @@ static unsigned long vmware_get_tsc_khz(void)
>  	return vmware_tsc_khz;
>  }
>  
> +#ifdef CONFIG_PARAVIRT
> +static void __init vmware_paravirt_ops_setup(void)
> +{
> +	pv_info.name = "VMware";
> +	pv_cpu_ops.io_delay = paravirt_nop;
> +}
> +#else
> +#define vmware_paravirt_ops_setup() do {} while (0)
> +#endif
> +
>  static void __init vmware_platform_setup(void)
>  {
>  	uint32_t eax, ebx, ecx, edx;
> @@ -94,6 +104,8 @@ static void __init vmware_platform_setup(void)
>  	} else {
>  		pr_warn("Failed to get TSC freq from the hypervisor\n");
>  	}
> +
> +	vmware_paravirt_ops_setup();
>  }
>  
>  /*



-- 
Tim Mann                  | work: mann@vmware.com  home: tim@tim-mann.org
VMware Sr. Staff Engineer | http://www.vmware.com  http://tim-mann.org

Re: [PATCH 2/3] x86/vmware: Add basic paravirt ops support

[Thomas Gleixner]

On Wed, 26 Oct 2016, Tim Mann wrote:

> I believe our trademark guidelines say we aren't supposed to use VMware as a
> noun to mean a product, only to mean the company.  So we can say "running on
> VMware ESXi" or "running in a VMware virtual machine", but "running on VMware"
> is wrong.  There is supposedly some good legal reason for this related to
> keeping our trademark.

Please sort that out internally and resend the whole lot when this is
resolved.

Thanks,

	tglx

[RESEND PATCH 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu()

[Alexey Makhalov]

After aa297292d708, there are separate native calibrations for cpu_khz and
tsc_khz. The code sets x86_platform.calibrate_cpu to native_calibrate_cpu()
which looks in cpuid leaf 0x16 or msrs for the cpu frequency. Since we keep
the tsc_khz constant (even after vmotion), the cpu_khz and tsc_khz may
start diverging.

tsc_init() now does

	cpu_khz = x86_platform.calibrate_cpu();
	tsc_khz = x86_platform.calibrate_tsc();
	if (tsc_khz == 0)
		tsc_khz = cpu_khz;
	else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
		cpu_khz = tsc_khz;

We want the cpu_khz and tsc_khz to be sync even if they diverge less then
10%.
This patch resolves this issue by setting x86_platform.calibrate_cpu to
vmware_get_tsc_khz().

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
---
 arch/x86/kernel/cpu/vmware.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 4e34da4b..480790f 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -83,6 +83,7 @@ static void __init vmware_platform_setup(void)
 
 		vmware_tsc_khz = tsc_khz;
 		x86_platform.calibrate_tsc = vmware_get_tsc_khz;
+		x86_platform.calibrate_cpu = vmware_get_tsc_khz;
 
 #ifdef CONFIG_X86_LOCAL_APIC
 		/* Skip lapic calibration since we know the bus frequency. */
-- 
2.10.1

[RESEND PATCH 2/3] x86/vmware: Add basic paravirt ops support

[Alexey Makhalov]

Add basic paravirt support:
 1. set pv_info.name to "VMware hypervisor" to have proper boot log message
	Booting paravirtualized kernel on VMware hypervisor
    instead of "... on bare hardware"
 2. set pv_cpu_ops.io_delay() to empty function - paravirt_nop() to
    avoid vm-exits on IO delays.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
---
 arch/x86/kernel/cpu/vmware.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 480790f..098a524 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -61,6 +61,16 @@ static unsigned long vmware_get_tsc_khz(void)
 	return vmware_tsc_khz;
 }
 
+#ifdef CONFIG_PARAVIRT
+static void __init vmware_paravirt_ops_setup(void)
+{
+	pv_info.name = "VMware hypervisor";
+	pv_cpu_ops.io_delay = paravirt_nop;
+}
+#else
+#define vmware_paravirt_ops_setup() do {} while (0)
+#endif
+
 static void __init vmware_platform_setup(void)
 {
 	uint32_t eax, ebx, ecx, edx;
@@ -94,6 +104,8 @@ static void __init vmware_platform_setup(void)
 	} else {
 		pr_warn("Failed to get TSC freq from the hypervisor\n");
 	}
+
+	vmware_paravirt_ops_setup();
 }
 
 /*
-- 
2.10.1

[RESEND PATCH 3/3] x86/vmware: Add paravirt sched clock

[Alexey Makhalov]

Set pv_time_ops.sched_clock to vmware_sched_clock(). It is simplified
version of native_sched_clock() without ring buffer of mult/shift/offset
triplets and preempt toggling.
Since VMware hypervisor provides constant tsc we can use constant
mult/shift/offset triplet calculated at boot time.

no-vmw-sched-clock kernel parameter is added to disable the paravirt
sched clock.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
---
 Documentation/kernel-parameters.txt |  4 ++++
 arch/x86/kernel/cpu/vmware.c        | 41 +++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 37babf9..b3b2ec0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2754,6 +2754,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
 			fault handling.
 
+	no-vmw-sched-clock
+			[X86,PV_OPS] Disable paravirtualized VMware scheduler
+			clock and use the default one.
+
 	no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
 			steal time is computed, but won't influence scheduler
 			behaviour
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 098a524..9b29511 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -24,10 +24,15 @@
 #include <linux/dmi.h>
 #include <linux/init.h>
 #include <linux/export.h>
+#include <linux/clocksource.h>
 #include <asm/div64.h>
 #include <asm/x86_init.h>
 #include <asm/hypervisor.h>
 #include <asm/apic.h>
+#include <asm/timer.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt)	"vmware: " fmt
 
 #define CPUID_VMWARE_INFO_LEAF	0x40000000
 #define VMWARE_HYPERVISOR_MAGIC	0x564D5868
@@ -62,10 +67,46 @@ static unsigned long vmware_get_tsc_khz(void)
 }
 
 #ifdef CONFIG_PARAVIRT
+static struct cyc2ns_data vmware_cyc2ns __ro_after_init;
+static int vmw_sched_clock __initdata = 1;
+
+static __init int setup_vmw_sched_clock(char *s)
+{
+	vmw_sched_clock = 0;
+	return 0;
+}
+early_param("no-vmw-sched-clock", setup_vmw_sched_clock);
+
+static unsigned long long vmware_sched_clock(void)
+{
+	unsigned long long ns;
+
+	ns = mul_u64_u32_shr(rdtsc(), vmware_cyc2ns.cyc2ns_mul,
+			     vmware_cyc2ns.cyc2ns_shift);
+	ns -= vmware_cyc2ns.cyc2ns_offset;
+	return ns;
+}
+
 static void __init vmware_paravirt_ops_setup(void)
 {
 	pv_info.name = "VMware hypervisor";
 	pv_cpu_ops.io_delay = paravirt_nop;
+
+	if (vmware_tsc_khz && vmw_sched_clock) {
+		unsigned long long tsc_now = rdtsc();
+
+		clocks_calc_mult_shift(&vmware_cyc2ns.cyc2ns_mul,
+				       &vmware_cyc2ns.cyc2ns_shift,
+				       vmware_tsc_khz,
+				       NSEC_PER_MSEC, 0);
+		vmware_cyc2ns.cyc2ns_offset =
+			mul_u64_u32_shr(tsc_now, vmware_cyc2ns.cyc2ns_mul,
+					vmware_cyc2ns.cyc2ns_shift);
+
+		pv_time_ops.sched_clock = vmware_sched_clock;
+		pr_info("using sched offset of %llu ns\n",
+			vmware_cyc2ns.cyc2ns_offset);
+	}
 }
 #else
 #define vmware_paravirt_ops_setup() do {} while (0)
-- 
2.10.1

Re: [RESEND PATCH 3/3] x86/vmware: Add paravirt sched clock

[Thomas Gleixner]

On Thu, 27 Oct 2016, Alexey Makhalov wrote:

> Set pv_time_ops.sched_clock to vmware_sched_clock(). 

Please do not describe WHAT the patch does, describe why. Describe the
problem you are solving. I can see from the patch

> +		pv_time_ops.sched_clock = vmware_sched_clock;

that you set pv_time_ops.sched_clock to vmware_sched_clock().

> It is simplified
> version of native_sched_clock() without ring buffer of mult/shift/offset
> triplets and preempt toggling.

-ENOPARSE

> Since VMware hypervisor provides constant tsc we can use constant
> mult/shift/offset triplet calculated at boot time.

So now you start to explain something which is understandable
 
> no-vmw-sched-clock kernel parameter is added to disable the paravirt
> sched clock.

I give you another example:

  The default sched_clock() implementation is native_sched_clock(). It
  contains code to handle non constant frequency TSCs, which creates
  overhead for systems with constant frequency TSCs.

  The vmware hypervisor guarantees a constant frequency TSC, so
  native_sched_clock() is not required and slower than a dedicated function
  which operates with one time calculated conversion factors.

  Calculate the conversion factors at boot time from the tsc frequency and
  install an optimized sched_clock() function via paravirt ops.

  The paravirtualized clock can be disabled on the kernel command line with
  the new 'no-vmw-sched-clock' option.

Can you see the difference and can you spot the structure similar to the
example I gave you before?

> +static unsigned long long vmware_sched_clock(void)
> +{
> +	unsigned long long ns;
> +
> +	ns = mul_u64_u32_shr(rdtsc(), vmware_cyc2ns.cyc2ns_mul,
> +			     vmware_cyc2ns.cyc2ns_shift);
> +	ns -= vmware_cyc2ns.cyc2ns_offset;
> +	return ns;
> +}
> +
>  static void __init vmware_paravirt_ops_setup(void)
>  {
>  	pv_info.name = "VMware hypervisor";
>  	pv_cpu_ops.io_delay = paravirt_nop;
> +
> +	if (vmware_tsc_khz && vmw_sched_clock) {
> +		unsigned long long tsc_now = rdtsc();
> +
> +		clocks_calc_mult_shift(&vmware_cyc2ns.cyc2ns_mul,
> +				       &vmware_cyc2ns.cyc2ns_shift,
> +				       vmware_tsc_khz,
> +				       NSEC_PER_MSEC, 0);
> +		vmware_cyc2ns.cyc2ns_offset =
> +			mul_u64_u32_shr(tsc_now, vmware_cyc2ns.cyc2ns_mul,
> +					vmware_cyc2ns.cyc2ns_shift);
> +
> +		pv_time_ops.sched_clock = vmware_sched_clock;
> +		pr_info("using sched offset of %llu ns\n",
> +			vmware_cyc2ns.cyc2ns_offset);

If you either do:

	if (!vmware_tsc_khz || !vmw_sched_clock)
		return;

or

	if (vmware_tsc_khz && vmw_sched_clock)
		setup_sched_clock();

and split out the code into a seperate function then you spare one
indentation level and some of these hard to read line breaks.

Hint:
	
static void setup_sched_clock(void)
{
	struct cyc2ns_data *d = &vmware_cyc2ns;

	clocks_calc_mult_shift(&d->cyc2ns_mul, &d->cyc32ns_shift,
			       vmware_tsc_khz, NSEC_PER_MSEC, 0);
	
reduces the lenght of the arguments significantly and makes this stuff sane
to read.

Thanks,

	tglx

Re: [RESEND PATCH 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu()

[Thomas Gleixner]

On Thu, 27 Oct 2016, Alexey Makhalov wrote:

> [RESEND PATCH 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu()

Please don't do that. RESEND is a keyword, when the same patch (series) is
sent again without any modification vs. the first patch (series). A
possible reason to do so is when a patch (series) fell through the cracks
and the author wants to bring it to attention again for the next merge
window.

If you send an updated patch (series) then please add Vn after PATCH, where
n is the version number of the patch (series).

While at it, please add a cover letter [PATCH Vn 0/n] the next time you send a
patch series. git send-email supports that.

> After aa297292d708, there are separate native calibrations for cpu_khz and

What is aa297292d708? 

Please make that:

commit aa297292d708 ("x86/tsc: Enumerate SKL cpu_khz and tsc_khz via
CPUID") .....

> tsc_khz. The code sets x86_platform.calibrate_cpu to native_calibrate_cpu()
> which looks in cpuid leaf 0x16 or msrs for the cpu frequency.

Which code? And what has the leaf and the msrs to do with your patch?

> Since we keep the tsc_khz constant (even after vmotion), the cpu_khz and
> tsc_khz may start diverging.

Now you talk about vmware related stuff, right?

> tsc_init() now does
> 
> 	cpu_khz = x86_platform.calibrate_cpu();
> 	tsc_khz = x86_platform.calibrate_tsc();
> 	if (tsc_khz == 0)
> 		tsc_khz = cpu_khz;
> 	else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
> 		cpu_khz = tsc_khz;

And here you copy from the referenced commit. How is that helpful?

> 
> We want the cpu_khz and tsc_khz to be sync even if they diverge less then
> 10%.

We? We as kernel developers, users, guest running in vmware ????

> This patch resolves this issue by setting x86_platform.calibrate_cpu to

"This patch" is just bad. We already know that this is a patch, otherwise
you wouldn't have sent it as a patch.

"this issue" - which issue? Your explanation above does not tell anything
what the issue is.

> vmware_get_tsc_khz().

Here is an example of a proper changelog for this (except for my potential
misinterpretation of the crypto message above):

  Commit aa297292d708 ("x86/tsc: Enumerate SKL cpu_khz and tsc_khz via
  CPUID") seperated the calibration mechanisms for cpu_khz and tsc_khz.

  In a vmware guest this change can lead to divergence between the tsc and
  the cpu frequency, because <Insert reason> .This causes <INSERT observed
  malfunction>.

  Due to the internal design of the vmware hypervisor <Replace that by real
  reason> it's required to keep tsc and cpu frequency in sync.

  Solve this by overriding the x86 platform cpu calibration callback with the
  vmware specific tsc calibration function.

So this describes very clearly:

   1) The change which causes the problem

   2) The problem itself and the resulting malfunction

   3) What needs to be achieved to solve the problem

   4) A short explanation what the solution is

Documentation/SubmittingPatches has further information about proper change
logs.

> @@ -83,6 +83,7 @@ static void __init vmware_platform_setup(void)
>  
>  		vmware_tsc_khz = tsc_khz;
>  		x86_platform.calibrate_tsc = vmware_get_tsc_khz;

A comment explaining why you set the cpu calibration to vmware_get_tsc_khz
might be helpful for casual readers and yourself when you look at that code
5 month from now.

> +		x86_platform.calibrate_cpu = vmware_get_tsc_khz;

Thanks,

	tglx

[PATCH v3 0/3] x86/vmware guest improvements

[Alexey Makhalov]

Thanks Thomas for the valuable comments.

Changelog for the updated patchset:
v1->v2 - Update pvinfo.name.
v2->v3 - Address comments from Thomas G,
	 * Created separate function: vmware_sched_clock_setup() (patch 3/3)
	 * Updated commit descriptions for 1/3 and 3/3


Alexey Makhalov (3):
  x86/vmware: Use tsc_khz value for calibrate_cpu()
  x86/vmware: Add basic paravirt ops support
  x86/vmware: Add paravirt sched clock

 Documentation/kernel-parameters.txt |  4 +++
 arch/x86/kernel/cpu/vmware.c        | 55 +++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)

-- 
2.10.1

[PATCH v3 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu()

[Alexey Makhalov]

Commit aa297292d708 ("x86/tsc: Enumerate SKL cpu_khz and tsc_khz via
CPUID") separated the calibration mechanisms for cpu_khz and tsc_khz.

Since the vmware hypervisor provides a constant frequency TSC to the guest,
this change can lead to divergence between the tsc and the cpu frequency
after vmotion, which might confuse the user.

Solve this by overriding the x86 platform cpu calibration callback with the
vmware specific tsc calibration function.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
---
 arch/x86/kernel/cpu/vmware.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 4e34da4b..480790f 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -83,6 +83,7 @@ static void __init vmware_platform_setup(void)
 
 		vmware_tsc_khz = tsc_khz;
 		x86_platform.calibrate_tsc = vmware_get_tsc_khz;
+		x86_platform.calibrate_cpu = vmware_get_tsc_khz;
 
 #ifdef CONFIG_X86_LOCAL_APIC
 		/* Skip lapic calibration since we know the bus frequency. */
-- 
2.10.1

[tip:x86/platform] x86/vmware: Use tsc_khz value for calibrate_cpu()

[tip-bot for Alexey Makhalov]

Commit-ID:  687bca8d664ac9b098005b57846773eb62040ae0
Gitweb:     http://git.kernel.org/tip/687bca8d664ac9b098005b57846773eb62040ae0
Author:     Alexey Makhalov <amakhalov@vmware.com>
AuthorDate: Fri, 28 Oct 2016 00:54:30 -0700
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 30 Oct 2016 08:57:07 +0100

x86/vmware: Use tsc_khz value for calibrate_cpu()

Commit aa297292d708 ("x86/tsc: Enumerate SKL cpu_khz and tsc_khz via
CPUID") separated the calibration mechanisms for cpu_khz and tsc_khz.

Since the vmware hypervisor provides a constant frequency TSC to the guest,
this change can lead to divergence between the tsc and the cpu frequency
after vmotion, which might confuse the user.

Solve this by overriding the x86 platform cpu calibration callback with the
vmware specific tsc calibration function.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
Cc: linux-doc@vger.kernel.org
Cc: pv-drivers@vmware.com
Cc: corbet@lwn.net
Cc: virtualization@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/20161028075432.90579-2-amakhalov@vmware.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 arch/x86/kernel/cpu/vmware.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 4e34da4b..480790f 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -83,6 +83,7 @@ static void __init vmware_platform_setup(void)
 
 		vmware_tsc_khz = tsc_khz;
 		x86_platform.calibrate_tsc = vmware_get_tsc_khz;
+		x86_platform.calibrate_cpu = vmware_get_tsc_khz;
 
 #ifdef CONFIG_X86_LOCAL_APIC
 		/* Skip lapic calibration since we know the bus frequency. */

[PATCH v3 2/3] x86/vmware: Add basic paravirt ops support

[Alexey Makhalov]

Add basic paravirt support:
 1. set pv_info.name to "VMware hypervisor" to have proper boot log message
	Booting paravirtualized kernel on VMware hypervisor
    instead of "... on bare hardware"
 2. set pv_cpu_ops.io_delay() to empty function - paravirt_nop() to
    avoid vm-exits on IO delays.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
---
 arch/x86/kernel/cpu/vmware.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 480790f..098a524 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -61,6 +61,16 @@ static unsigned long vmware_get_tsc_khz(void)
 	return vmware_tsc_khz;
 }
 
+#ifdef CONFIG_PARAVIRT
+static void __init vmware_paravirt_ops_setup(void)
+{
+	pv_info.name = "VMware hypervisor";
+	pv_cpu_ops.io_delay = paravirt_nop;
+}
+#else
+#define vmware_paravirt_ops_setup() do {} while (0)
+#endif
+
 static void __init vmware_platform_setup(void)
 {
 	uint32_t eax, ebx, ecx, edx;
@@ -94,6 +104,8 @@ static void __init vmware_platform_setup(void)
 	} else {
 		pr_warn("Failed to get TSC freq from the hypervisor\n");
 	}
+
+	vmware_paravirt_ops_setup();
 }
 
 /*
-- 
2.10.1

[tip:x86/platform] x86/vmware: Add basic paravirt ops support

[tip-bot for Alexey Makhalov]

Commit-ID:  91d1e54ebd1615d216b7f57324a5e69166a344e0
Gitweb:     http://git.kernel.org/tip/91d1e54ebd1615d216b7f57324a5e69166a344e0
Author:     Alexey Makhalov <amakhalov@vmware.com>
AuthorDate: Fri, 28 Oct 2016 00:54:31 -0700
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 30 Oct 2016 08:57:07 +0100

x86/vmware: Add basic paravirt ops support

Add basic paravirt support:

 1. Set pv_info.name to "VMware hypervisor" to have proper boot log message
	Booting paravirtualized kernel on VMware hypervisor
    instead of "... on bare hardware"

 2. Set pv_cpu_ops.io_delay() to empty function - paravirt_noop() to
    avoid vm-exits on IO delays because io delays they are not required.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
Cc: linux-doc@vger.kernel.org
Cc: pv-drivers@vmware.com
Cc: corbet@lwn.net
Cc: virtualization@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/20161028075432.90579-3-amakhalov@vmware.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 arch/x86/kernel/cpu/vmware.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 480790f..098a524 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -61,6 +61,16 @@ static unsigned long vmware_get_tsc_khz(void)
 	return vmware_tsc_khz;
 }
 
+#ifdef CONFIG_PARAVIRT
+static void __init vmware_paravirt_ops_setup(void)
+{
+	pv_info.name = "VMware hypervisor";
+	pv_cpu_ops.io_delay = paravirt_nop;
+}
+#else
+#define vmware_paravirt_ops_setup() do {} while (0)
+#endif
+
 static void __init vmware_platform_setup(void)
 {
 	uint32_t eax, ebx, ecx, edx;
@@ -94,6 +104,8 @@ static void __init vmware_platform_setup(void)
 	} else {
 		pr_warn("Failed to get TSC freq from the hypervisor\n");
 	}
+
+	vmware_paravirt_ops_setup();
 }
 
 /*

[PATCH v3 3/3] x86/vmware: Add paravirt sched clock

[Alexey Makhalov]

The default sched_clock() implementation is native_sched_clock(). It
contains code to handle non constant frequency TSCs, which creates
overhead for systems with constant frequency TSCs.

The vmware hypervisor guarantees a constant frequency TSC, so
native_sched_clock() is not required and slower than a dedicated function
which operates with one time calculated conversion factors.

Calculate the conversion factors at boot time from the tsc frequency and
install an optimized sched_clock() function via paravirt ops.

The paravirtualized clock can be disabled on the kernel command line with
the new 'no-vmw-sched-clock' option.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
---
 Documentation/kernel-parameters.txt |  4 ++++
 arch/x86/kernel/cpu/vmware.c        | 42 +++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 37babf9..b3b2ec0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2754,6 +2754,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
 			fault handling.
 
+	no-vmw-sched-clock
+			[X86,PV_OPS] Disable paravirtualized VMware scheduler
+			clock and use the default one.
+
 	no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
 			steal time is computed, but won't influence scheduler
 			behaviour
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 098a524..cdbe38b 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -24,10 +24,15 @@
 #include <linux/dmi.h>
 #include <linux/init.h>
 #include <linux/export.h>
+#include <linux/clocksource.h>
 #include <asm/div64.h>
 #include <asm/x86_init.h>
 #include <asm/hypervisor.h>
 #include <asm/apic.h>
+#include <asm/timer.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt)	"vmware: " fmt
 
 #define CPUID_VMWARE_INFO_LEAF	0x40000000
 #define VMWARE_HYPERVISOR_MAGIC	0x564D5868
@@ -62,10 +67,47 @@ static unsigned long vmware_get_tsc_khz(void)
 }
 
 #ifdef CONFIG_PARAVIRT
+static struct cyc2ns_data vmware_cyc2ns __ro_after_init;
+static int vmw_sched_clock __initdata = 1;
+
+static __init int setup_vmw_sched_clock(char *s)
+{
+	vmw_sched_clock = 0;
+	return 0;
+}
+early_param("no-vmw-sched-clock", setup_vmw_sched_clock);
+
+static unsigned long long vmware_sched_clock(void)
+{
+	unsigned long long ns;
+
+	ns = mul_u64_u32_shr(rdtsc(), vmware_cyc2ns.cyc2ns_mul,
+			     vmware_cyc2ns.cyc2ns_shift);
+	ns -= vmware_cyc2ns.cyc2ns_offset;
+	return ns;
+}
+
+static void __init vmware_sched_clock_setup(void)
+{
+	struct cyc2ns_data *d = &vmware_cyc2ns;
+	unsigned long long tsc_now = rdtsc();
+
+	clocks_calc_mult_shift(&d->cyc2ns_mul, &d->cyc2ns_shift,
+			       vmware_tsc_khz, NSEC_PER_MSEC, 0);
+	d->cyc2ns_offset = mul_u64_u32_shr(tsc_now, d->cyc2ns_mul,
+					   d->cyc2ns_shift);
+
+	pv_time_ops.sched_clock = vmware_sched_clock;
+	pr_info("using sched offset of %llu ns\n", d->cyc2ns_offset);
+}
+
 static void __init vmware_paravirt_ops_setup(void)
 {
 	pv_info.name = "VMware hypervisor";
 	pv_cpu_ops.io_delay = paravirt_nop;
+
+	if (vmware_tsc_khz && vmw_sched_clock)
+		vmware_sched_clock_setup();
 }
 #else
 #define vmware_paravirt_ops_setup() do {} while (0)
-- 
2.10.1

[tip:x86/platform] x86/vmware: Add paravirt sched clock

[tip-bot for Alexey Makhalov]

Commit-ID:  80e9a4f21fd7ccce7e9b8439986fd028c9946dda
Gitweb:     http://git.kernel.org/tip/80e9a4f21fd7ccce7e9b8439986fd028c9946dda
Author:     Alexey Makhalov <amakhalov@vmware.com>
AuthorDate: Fri, 28 Oct 2016 00:54:32 -0700
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 30 Oct 2016 08:57:08 +0100

x86/vmware: Add paravirt sched clock

The default sched_clock() implementation is native_sched_clock(). It
contains code to handle non constant frequency TSCs, which creates
overhead for systems with constant frequency TSCs.

The vmware hypervisor guarantees a constant frequency TSC, so
native_sched_clock() is not required and slower than a dedicated function
which operates with one time calculated conversion factors.

Calculate the conversion factors at boot time from the tsc frequency and
install an optimized sched_clock() function via paravirt ops.

The paravirtualized clock can be disabled on the kernel command line with
the new 'no-vmw-sched-clock' option.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
Cc: linux-doc@vger.kernel.org
Cc: pv-drivers@vmware.com
Cc: corbet@lwn.net
Cc: virtualization@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/20161028075432.90579-4-amakhalov@vmware.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 Documentation/kernel-parameters.txt |  4 ++++
 arch/x86/kernel/cpu/vmware.c        | 42 +++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 37babf9..b3b2ec0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2754,6 +2754,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
 			fault handling.
 
+	no-vmw-sched-clock
+			[X86,PV_OPS] Disable paravirtualized VMware scheduler
+			clock and use the default one.
+
 	no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
 			steal time is computed, but won't influence scheduler
 			behaviour
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 098a524..cdbe38b 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -24,10 +24,15 @@
 #include <linux/dmi.h>
 #include <linux/init.h>
 #include <linux/export.h>
+#include <linux/clocksource.h>
 #include <asm/div64.h>
 #include <asm/x86_init.h>
 #include <asm/hypervisor.h>
 #include <asm/apic.h>
+#include <asm/timer.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt)	"vmware: " fmt
 
 #define CPUID_VMWARE_INFO_LEAF	0x40000000
 #define VMWARE_HYPERVISOR_MAGIC	0x564D5868
@@ -62,10 +67,47 @@ static unsigned long vmware_get_tsc_khz(void)
 }
 
 #ifdef CONFIG_PARAVIRT
+static struct cyc2ns_data vmware_cyc2ns __ro_after_init;
+static int vmw_sched_clock __initdata = 1;
+
+static __init int setup_vmw_sched_clock(char *s)
+{
+	vmw_sched_clock = 0;
+	return 0;
+}
+early_param("no-vmw-sched-clock", setup_vmw_sched_clock);
+
+static unsigned long long vmware_sched_clock(void)
+{
+	unsigned long long ns;
+
+	ns = mul_u64_u32_shr(rdtsc(), vmware_cyc2ns.cyc2ns_mul,
+			     vmware_cyc2ns.cyc2ns_shift);
+	ns -= vmware_cyc2ns.cyc2ns_offset;
+	return ns;
+}
+
+static void __init vmware_sched_clock_setup(void)
+{
+	struct cyc2ns_data *d = &vmware_cyc2ns;
+	unsigned long long tsc_now = rdtsc();
+
+	clocks_calc_mult_shift(&d->cyc2ns_mul, &d->cyc2ns_shift,
+			       vmware_tsc_khz, NSEC_PER_MSEC, 0);
+	d->cyc2ns_offset = mul_u64_u32_shr(tsc_now, d->cyc2ns_mul,
+					   d->cyc2ns_shift);
+
+	pv_time_ops.sched_clock = vmware_sched_clock;
+	pr_info("using sched offset of %llu ns\n", d->cyc2ns_offset);
+}
+
 static void __init vmware_paravirt_ops_setup(void)
 {
 	pv_info.name = "VMware hypervisor";
 	pv_cpu_ops.io_delay = paravirt_nop;
+
+	if (vmware_tsc_khz && vmw_sched_clock)
+		vmware_sched_clock_setup();
 }
 #else
 #define vmware_paravirt_ops_setup() do {} while (0)

[PATCH 3/3] x86/vmware: Add paravirt sched clock

[Alexey Makhalov]

Set pv_time_ops.sched_clock to vmware_sched_clock(). It is simplified
version of native_sched_clock() without ring buffer of mult/shift/offset
triplets and preempt toggling.
Since VMware hypervisor provides constant tsc we can use constant
mult/shift/offset triplet calculated at boot time.

no-vmw-sched-clock kernel parameter is added to switch back to the
native_sched_clock() implementation.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
---
 Documentation/kernel-parameters.txt |  4 ++++
 arch/x86/kernel/cpu/vmware.c        | 38 +++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 37babf9..b3b2ec0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2754,6 +2754,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
 			fault handling.
 
+	no-vmw-sched-clock
+			[X86,PV_OPS] Disable paravirtualized VMware scheduler
+			clock and use the default one.
+
 	no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
 			steal time is computed, but won't influence scheduler
 			behaviour
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index e3fb320..6ef22c1 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -24,10 +24,12 @@
 #include <linux/dmi.h>
 #include <linux/init.h>
 #include <linux/export.h>
+#include <linux/clocksource.h>
 #include <asm/div64.h>
 #include <asm/x86_init.h>
 #include <asm/hypervisor.h>
 #include <asm/apic.h>
+#include <asm/timer.h>
 
 #define CPUID_VMWARE_INFO_LEAF	0x40000000
 #define VMWARE_HYPERVISOR_MAGIC	0x564D5868
@@ -62,10 +64,46 @@ static unsigned long vmware_get_tsc_khz(void)
 }
 
 #ifdef CONFIG_PARAVIRT
+static struct cyc2ns_data vmware_cyc2ns __ro_after_init;
+
+static int vmw_sched_clock __initdata = 1;
+static __init int setup_vmw_sched_clock(char *s)
+{
+	vmw_sched_clock = 0;
+	return 0;
+}
+early_param("no-vmw-sched-clock", setup_vmw_sched_clock);
+
+static unsigned long long vmware_sched_clock(void)
+{
+	unsigned long long ns;
+
+	ns = mul_u64_u32_shr(rdtsc(), vmware_cyc2ns.cyc2ns_mul,
+			     vmware_cyc2ns.cyc2ns_shift);
+	ns -= vmware_cyc2ns.cyc2ns_offset;
+	return ns;
+}
+
 static void __init vmware_paravirt_ops_setup(void)
 {
 	pv_info.name = "VMware";
 	pv_cpu_ops.io_delay = paravirt_nop;
+
+	if (vmware_tsc_khz && vmw_sched_clock) {
+		unsigned long long tsc_now = rdtsc();
+
+		clocks_calc_mult_shift(&vmware_cyc2ns.cyc2ns_mul,
+				       &vmware_cyc2ns.cyc2ns_shift,
+				       vmware_tsc_khz,
+				       NSEC_PER_MSEC, 0);
+		vmware_cyc2ns.cyc2ns_offset =
+			mul_u64_u32_shr(tsc_now, vmware_cyc2ns.cyc2ns_mul,
+					vmware_cyc2ns.cyc2ns_shift);
+
+		pv_time_ops.sched_clock = vmware_sched_clock;
+		pr_info("vmware: using sched offset of %llu ns\n",
+			vmware_cyc2ns.cyc2ns_offset);
+	}
 }
 #else
 #define vmware_paravirt_ops_setup() do {} while (0)
-- 
2.10.1

Re: [PATCH 3/3] x86/vmware: Add paravirt sched clock

[Thomas Gleixner]

On Tue, 25 Oct 2016, Alexey Makhalov wrote:
> no-vmw-sched-clock kernel parameter is added to switch back to the
> native_sched_clock() implementation.

You are not switching back. The parameter is used to disable the paravirt
sched clock.

>  #ifdef CONFIG_PARAVIRT
> +static struct cyc2ns_data vmware_cyc2ns __ro_after_init;
> +
> +static int vmw_sched_clock __initdata = 1;
> +static __init int setup_vmw_sched_clock(char *s)

Please stop glueing a variable to a function w/o a new line between
them. It's just stopping the reading flow.

> +{
> +	vmw_sched_clock = 0;
> +	return 0;
> +}
> +early_param("no-vmw-sched-clock", setup_vmw_sched_clock);
> +
> +static unsigned long long vmware_sched_clock(void)
> +{
> +	unsigned long long ns;
> +
> +	ns = mul_u64_u32_shr(rdtsc(), vmware_cyc2ns.cyc2ns_mul,
> +			     vmware_cyc2ns.cyc2ns_shift);
> +	ns -= vmware_cyc2ns.cyc2ns_offset;
> +	return ns;
> +}
> +
>  static void __init vmware_paravirt_ops_setup(void)
>  {
>  	pv_info.name = "VMware";
>  	pv_cpu_ops.io_delay = paravirt_nop;
> +
> +	if (vmware_tsc_khz && vmw_sched_clock) {
> +		unsigned long long tsc_now = rdtsc();
> +
> +		clocks_calc_mult_shift(&vmware_cyc2ns.cyc2ns_mul,
> +				       &vmware_cyc2ns.cyc2ns_shift,
> +				       vmware_tsc_khz,
> +				       NSEC_PER_MSEC, 0);
> +		vmware_cyc2ns.cyc2ns_offset =
> +			mul_u64_u32_shr(tsc_now, vmware_cyc2ns.cyc2ns_mul,
> +					vmware_cyc2ns.cyc2ns_shift);
> +
> +		pv_time_ops.sched_clock = vmware_sched_clock;
> +		pr_info("vmware: using sched offset of %llu ns\n",

Please use pr_fmt instead of adding the prefix to every print.

Thanks,

	tglx

[PATCH v2 3/3] x86/vmware: Add paravirt sched clock

[Alexey Makhalov]

Set pv_time_ops.sched_clock to vmware_sched_clock(). It is simplified
version of native_sched_clock() without ring buffer of mult/shift/offset
triplets and preempt toggling.
Since VMware hypervisor provides constant tsc we can use constant
mult/shift/offset triplet calculated at boot time.

no-vmw-sched-clock kernel parameter is added to disable the paravirt
sched clock.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
---
 Documentation/kernel-parameters.txt |  4 ++++
 arch/x86/kernel/cpu/vmware.c        | 41 +++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 37babf9..b3b2ec0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2754,6 +2754,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
 			fault handling.
 
+	no-vmw-sched-clock
+			[X86,PV_OPS] Disable paravirtualized VMware scheduler
+			clock and use the default one.
+
 	no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
 			steal time is computed, but won't influence scheduler
 			behaviour
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index e3fb320..e284ebf 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -24,10 +24,15 @@
 #include <linux/dmi.h>
 #include <linux/init.h>
 #include <linux/export.h>
+#include <linux/clocksource.h>
 #include <asm/div64.h>
 #include <asm/x86_init.h>
 #include <asm/hypervisor.h>
 #include <asm/apic.h>
+#include <asm/timer.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt)	"vmware: " fmt
 
 #define CPUID_VMWARE_INFO_LEAF	0x40000000
 #define VMWARE_HYPERVISOR_MAGIC	0x564D5868
@@ -62,10 +67,46 @@ static unsigned long vmware_get_tsc_khz(void)
 }
 
 #ifdef CONFIG_PARAVIRT
+static struct cyc2ns_data vmware_cyc2ns __ro_after_init;
+static int vmw_sched_clock __initdata = 1;
+
+static __init int setup_vmw_sched_clock(char *s)
+{
+	vmw_sched_clock = 0;
+	return 0;
+}
+early_param("no-vmw-sched-clock", setup_vmw_sched_clock);
+
+static unsigned long long vmware_sched_clock(void)
+{
+	unsigned long long ns;
+
+	ns = mul_u64_u32_shr(rdtsc(), vmware_cyc2ns.cyc2ns_mul,
+			     vmware_cyc2ns.cyc2ns_shift);
+	ns -= vmware_cyc2ns.cyc2ns_offset;
+	return ns;
+}
+
 static void __init vmware_paravirt_ops_setup(void)
 {
 	pv_info.name = "VMware";
 	pv_cpu_ops.io_delay = paravirt_nop;
+
+	if (vmware_tsc_khz && vmw_sched_clock) {
+		unsigned long long tsc_now = rdtsc();
+
+		clocks_calc_mult_shift(&vmware_cyc2ns.cyc2ns_mul,
+				       &vmware_cyc2ns.cyc2ns_shift,
+				       vmware_tsc_khz,
+				       NSEC_PER_MSEC, 0);
+		vmware_cyc2ns.cyc2ns_offset =
+			mul_u64_u32_shr(tsc_now, vmware_cyc2ns.cyc2ns_mul,
+					vmware_cyc2ns.cyc2ns_shift);
+
+		pv_time_ops.sched_clock = vmware_sched_clock;
+		pr_info("using sched offset of %llu ns\n",
+			vmware_cyc2ns.cyc2ns_offset);
+	}
 }
 #else
 #define vmware_paravirt_ops_setup() do {} while (0)
-- 
2.10.1