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x86: Get TSC frequency from VMware hypervisor.

PATCH In review Alok Kataria 2 participants 5 messages Oct 21, 2008 – Oct 22, 2008 x86

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Alok Kataria

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#0 lore raw

PATCH 2/3 x86: Get TSC frequency from VMware hypervisor.

x86: Get TSC frequency from VMware hypervisor.

From: Alok N Kataria <[email protected]>

This patch adds functions to detect if we are running under VMware. The current way to check if we are on VMware is following, # check if "hypervisor present bit" is set, if so read the 0x40000000
cpuid leaf and check for "VMwareVMware" signature.
# if the above fails, check the DMI vendors name for "VMware" string
if we find one we query the VMware backdoor port to check if we are under VMware.

The DMI + Backdoor check is needed for older VMware products, which don't implement the hypervisor signature cpuid leaf.
Also note that since we are checking for the DMI signature the backdoor port would never be accessed on native hardware.

This patch also adds a hypervisor_get_tsc_freq function, instead of calibrating the frequency which can be error prone in virtualized environment, we ask the hypervisor for it. We get the frequency from the hypervisor by accessing the backdoor port if we are running on VMware. Other hypervisors too can add code to get frequency on their platform to this routine.

Signed-off-by Alok N Kataria <[email protected]>

---

 arch/x86/kernel/Makefile     |    2 -
 arch/x86/kernel/tsc.c        |   16 +++++++-
 arch/x86/kernel/vmware.c     |   87 ++++++++++++++++++++++++++++++++++++++++++
 include/asm-x86/cpufeature.h |    2 +
 include/asm-x86/vmware.h     |   26 +++++++++++++
 5 files changed, 131 insertions(+), 2 deletions(-)
 create mode 100644 arch/x86/kernel/vmware.c
 create mode 100644 include/asm-x86/vmware.h
arch/x86/kernel/Makefile +1 -1
index 01dc4c7..bca729b 100644
@@ -35,7 +35,7 @@ obj-$(CONFIG_X86_64)	+= syscall_64.o vsyscall_64.o
 obj-y			+= bootflag.o e820.o
 obj-y			+= pci-dma.o quirks.o i8237.o topology.o kdebugfs.o
 obj-y			+= alternative.o i8253.o pci-nommu.o
-obj-y			+= tsc.o io_delay.o rtc.o
+obj-y			+= tsc.o io_delay.o rtc.o vmware.o
 
 obj-$(CONFIG_X86_TRAMPOLINE)	+= trampoline.o
 obj-y				+= process.o
arch/x86/kernel/tsc.c +15 -1
index 161bb85..355252f 100644
@@ -15,6 +15,7 @@
 #include <asm/vgtod.h>
 #include <asm/time.h>
 #include <asm/delay.h>
+#include <asm/vmware.h>
 
 unsigned int cpu_khz;           /* TSC clocks / usec, not used here */
 EXPORT_SYMBOL(cpu_khz);

@@ -345,6 +346,13 @@ failed:
 	return 0;
 }
 
+static unsigned long get_hypervisor_tsc_freq(void)
+{
+	if (vmware_platform())
+		return vmware_get_tsc_khz();
+	return 0;
+}
+
 /**
  * native_calibrate_tsc - calibrate the tsc on boot
  */

@@ -352,9 +360,15 @@ unsigned long native_calibrate_tsc(void)
 {
 	u64 tsc1, tsc2, delta, ref1, ref2;
 	unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX;
-	unsigned long flags, latch, ms, fast_calibrate;
+	unsigned long flags, latch, ms, fast_calibrate, tsc_khz;
 	int hpet = is_hpet_enabled(), i, loopmin;
 
+	tsc_khz = get_hypervisor_tsc_freq();
+	if (tsc_khz) {
+		printk(KERN_INFO "TSC: Frequency read from the hypervisor\n");
+		return tsc_khz;
+	}
+
 	local_irq_save(flags);
 	fast_calibrate = quick_pit_calibrate();
 	local_irq_restore(flags);
arch/x86/kernel/vmware.c new file +87 -0

87 lines not on this page · raw message

include/asm-x86/cpufeature.h +2 -0
index adfeae6..f891dfc 100644
@@ -117,6 +117,7 @@
 #define X86_FEATURE_XSAVE	(4*32+26) /* XSAVE/XRSTOR/XSETBV/XGETBV */
 #define X86_FEATURE_OSXSAVE	(4*32+27) /* "" XSAVE enabled in the OS */
 #define X86_FEATURE_AVX		(4*32+28) /* Advanced Vector Extensions */
+#define X86_FEATURE_HYPERVISOR	(4*32+31) /* Running on a hypervisor */
 
 /* VIA/Cyrix/Centaur-defined CPU features, CPUID level 0xC0000001, word 5 */
 #define X86_FEATURE_XSTORE	(5*32+ 2) /* "rng" RNG present (xstore) */

@@ -237,6 +238,7 @@ extern const char * const x86_power_flags[32];
 #define cpu_has_xmm4_2		boot_cpu_has(X86_FEATURE_XMM4_2)
 #define cpu_has_x2apic		boot_cpu_has(X86_FEATURE_X2APIC)
 #define cpu_has_xsave		boot_cpu_has(X86_FEATURE_XSAVE)
+#define cpu_has_hypervisor	boot_cpu_has(X86_FEATURE_HYPERVISOR)
 
 #if defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_64)
 # define cpu_has_invlpg		1
include/asm-x86/vmware.h new file +26 -0
new file mode 100644
index 0000000..02dfea5
@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2008, VMware, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+#ifndef ASM_X86__VMWARE_H
+#define ASM_X86__VMWARE_H
+
+extern unsigned long vmware_get_tsc_khz(void);
+extern int vmware_platform(void);
+
+#endif
reviewer
#1 lore raw
Quoted 17 lines · Alok Kataria

x86: Get TSC frequency from VMware hypervisor.

From: Alok N Kataria <[email protected]>

This patch adds functions to detect if we are running under VMware. The current way to check if we are on VMware is following, # check if "hypervisor present bit" is set, if so read the 0x40000000
cpuid leaf and check for "VMwareVMware" signature.
# if the above fails, check the DMI vendors name for "VMware" string
if we find one we query the VMware backdoor port to check if we are under VMware.

The DMI + Backdoor check is needed for older VMware products, which don't implement the hypervisor signature cpuid leaf.
Also note that since we are checking for the DMI signature the backdoor port would never be accessed on native hardware.

Quoted 7 lines

This patch also adds a hypervisor_get_tsc_freq function, instead of calibrating the frequency which can be error prone in virtualized environment, we ask the hypervisor for it. We get the frequency from the hypervisor by accessing the backdoor port if we are running on VMware. Other hypervisors too can add code to get frequency on their platform to this routine.

I would like to see, instead of calling vmware_platform() directly in places like tsc.c, a hypervisor field in the CPU structure that is set with the rest of the CPU identification stuff. That way we avoid ending up with garbage like:

if (vmware_platform() || xen_platform() || kvm_platform() ...)

-hpa

author
#2 lore raw
Quoted 26 lines · H. Peter Anvin
Quoted 17 lines · Alok Kataria

x86: Get TSC frequency from VMware hypervisor.

From: Alok N Kataria <[email protected]>

This patch adds functions to detect if we are running under VMware. The current way to check if we are on VMware is following, # check if "hypervisor present bit" is set, if so read the 0x40000000
cpuid leaf and check for "VMwareVMware" signature.
# if the above fails, check the DMI vendors name for "VMware" string
if we find one we query the VMware backdoor port to check if we are under VMware.

The DMI + Backdoor check is needed for older VMware products, which don't implement the hypervisor signature cpuid leaf.
Also note that since we are checking for the DMI signature the backdoor port would never be accessed on native hardware.

Quoted 7 lines

This patch also adds a hypervisor_get_tsc_freq function, instead of calibrating the frequency which can be error prone in virtualized environment, we ask the hypervisor for it. We get the frequency from the hypervisor by accessing the backdoor port if we are running on VMware. Other hypervisors too can add code to get frequency on their platform to this routine.

Quoted 3 lines

I would like to see, instead of calling vmware_platform() directly in places like tsc.c, a hypervisor field in the CPU structure that is set with the rest of the CPU identification stuff.

Hi hpa,

Do you mean we should have a x86_hyper_vendor field in cpuinfo_x86 ? Even with that, i think we will have to differentiate between each of the hypervisors, as each of the hypervisor implementation differs in how they provide the TSC frequency.

So we would end up with code like,

	if (boot_cpu.x86_hyper_vendor == VMWARE)
		get_frequency_vmware_way();
	if (boot_cpu.x86_hyper_vendor == XXX)
		get_frequency_XXX_way();

I agree that having a field in the cpu structure will make sure that we don't end up calling vmware_platform multiple times, but does it help in this particular situation ?

Let me know if you meant something else.

Thanks,
Alok

Quoted 6 lines

That way we avoid ending
up with garbage like:

if (vmware_platform() || xen_platform() || kvm_platform() ...)

-hpa

reviewer
#3 lore raw
Quoted 13 lines · Alok Kataria

Hi hpa,

Do you mean we should have a x86_hyper_vendor field in cpuinfo_x86 ? Even with that, i think we will have to differentiate between each of the hypervisors, as each of the hypervisor implementation differs in how
they provide the TSC frequency.

So we would end up with code like,

	if (boot_cpu.x86_hyper_vendor == VMWARE)
		get_frequency_vmware_way();
	if (boot_cpu.x86_hyper_vendor == XXX)
		get_frequency_XXX_way();
Quoted 6 lines

I agree that having a field in the cpu structure will make sure that we don't end up calling vmware_platform multiple times, but does it help in this particular situation ?

Let me know if you meant something else.

That's exactly what I mean. I want the detection centralized, and no, with only one user it doesn't make much difference, but there won't be just one user.

-hpa

author
#4 lore raw

Hi hpa,
below is the v2 of this patch.

--

x86: Get TSC frequency from VMware hypervisor.

From: Alok N Kataria <[email protected]>

v2->v1 : Add a x86_hyper_vendor field to the cpuinfo_x86 structure.
This avoids multiple calls to the hypervisor detection function.

This patch adds functions to detect if we are running under VMware. The current way to check if we are on VMware is following, # check if "hypervisor present bit" is set, if so read the 0x40000000
cpuid leaf and check for "VMwareVMware" signature.
# if the above fails, check the DMI vendors name for "VMware" string
if we find one we query the VMware backdoor port to check if we are under VMware.

The DMI + Backdoor check is needed for older VMware products, which don't implement the hypervisor signature cpuid leaf.
Also note that since we are checking for the DMI signature the backdoor port would never be accessed on native hardware.

This patch also adds a hypervisor_get_tsc_freq function, instead of calibrating the frequency which can be error prone in virtualized environment, we ask the hypervisor for it. We get the frequency from the hypervisor by accessing the backdoor port if we are running on VMware. Other hypervisors too can add code to get frequency on their platform to this routine.

Signed-off-by Alok N Kataria <[email protected]>
Cc H. Peter Anvin <[email protected]>

---

 arch/x86/kernel/Makefile     |    2 -
 arch/x86/kernel/cpu/common.c |   10 +++++
 arch/x86/kernel/setup.c      |    6 +++
 arch/x86/kernel/tsc.c        |   16 +++++++-
 arch/x86/kernel/vmware.c     |   87 ++++++++++++++++++++++++++++++++++++++++++
 include/asm-x86/cpufeature.h |    2 +
 include/asm-x86/processor.h  |    6 +++
 include/asm-x86/vmware.h     |   26 +++++++++++++
 8 files changed, 153 insertions(+), 2 deletions(-)
 create mode 100644 arch/x86/kernel/vmware.c
 create mode 100644 include/asm-x86/vmware.h
arch/x86/kernel/Makefile +1 -1
index 01dc4c7..bca729b 100644
@@ -35,7 +35,7 @@ obj-$(CONFIG_X86_64)	+= syscall_64.o vsyscall_64.o
 obj-y			+= bootflag.o e820.o
 obj-y			+= pci-dma.o quirks.o i8237.o topology.o kdebugfs.o
 obj-y			+= alternative.o i8253.o pci-nommu.o
-obj-y			+= tsc.o io_delay.o rtc.o
+obj-y			+= tsc.o io_delay.o rtc.o vmware.o
 
 obj-$(CONFIG_X86_TRAMPOLINE)	+= trampoline.o
 obj-y				+= process.o
arch/x86/kernel/cpu/common.c +10 -0
index ff26d87..a48cb0e 100644
@@ -448,6 +448,15 @@ void __cpuinit cpu_detect(struct cpuinfo_x86 *c)
 	}
 }
 
+void __cpuinit detect_hypervisor_vendor(struct cpuinfo_x86 *c)
+{
+	if (vmware_platform()) {
+		c->x86_hyper_vendor = X86_HYPER_VENDOR_VMWARE;
+	} else {
+		c->x86_hyper_vendor = X86_HYPER_VENDOR_NONE;
+	}
+}
+
 static void __cpuinit get_cpu_cap(struct cpuinfo_x86 *c)
 {
 	u32 tfms, xlvl;

@@ -702,6 +711,7 @@ static void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
 	detect_ht(c);
 #endif
 
+	detect_hypervisor_vendor(c);
 	/*
 	 * On SMP, boot_cpu_data holds the common feature set between
 	 * all CPUs; so make sure that we indicate which features are
arch/x86/kernel/setup.c +6 -0
index 343f3a9..b6b11f9 100644
@@ -905,6 +905,12 @@ void __init setup_arch(char **cmdline_p)
 
 	dmi_check_system(bad_bios_dmi_table);
 
+	/* 
+	 * VMware detection requires dmi to be available,
+	 * so this needs to be done after dmi_scan_machine.
+	 */  
+	detect_hypervisor_vendor(&boot_cpu_data);
+
 #ifdef CONFIG_X86_32
 	probe_roms();
 #endif
arch/x86/kernel/tsc.c +15 -1
index 161bb85..4ae207c 100644
@@ -15,6 +15,7 @@
 #include <asm/vgtod.h>
 #include <asm/time.h>
 #include <asm/delay.h>
+#include <asm/vmware.h>
 
 unsigned int cpu_khz;           /* TSC clocks / usec, not used here */
 EXPORT_SYMBOL(cpu_khz);

@@ -345,6 +346,13 @@ failed:
 	return 0;
 }
 
+static unsigned long get_hypervisor_tsc_freq(void)
+{
+	if (boot_cpu_data.x86_hyper_vendor == X86_HYPER_VENDOR_VMWARE)
+		return vmware_get_tsc_khz();
+	return 0;
+}
+
 /**
  * native_calibrate_tsc - calibrate the tsc on boot
  */

@@ -352,9 +360,15 @@ unsigned long native_calibrate_tsc(void)
 {
 	u64 tsc1, tsc2, delta, ref1, ref2;
 	unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX;
-	unsigned long flags, latch, ms, fast_calibrate;
+	unsigned long flags, latch, ms, fast_calibrate, tsc_khz;
 	int hpet = is_hpet_enabled(), i, loopmin;
 
+	tsc_khz = get_hypervisor_tsc_freq();
+	if (tsc_khz) {
+		printk(KERN_INFO "TSC: Frequency read from the hypervisor\n");
+		return tsc_khz;
+	}
+
 	local_irq_save(flags);
 	fast_calibrate = quick_pit_calibrate();
 	local_irq_restore(flags);
arch/x86/kernel/vmware.c new file +87 -0

87 lines not on this page · raw message

include/asm-x86/cpufeature.h +2 -0
index adfeae6..f891dfc 100644
@@ -117,6 +117,7 @@
 #define X86_FEATURE_XSAVE	(4*32+26) /* XSAVE/XRSTOR/XSETBV/XGETBV */
 #define X86_FEATURE_OSXSAVE	(4*32+27) /* "" XSAVE enabled in the OS */
 #define X86_FEATURE_AVX		(4*32+28) /* Advanced Vector Extensions */
+#define X86_FEATURE_HYPERVISOR	(4*32+31) /* Running on a hypervisor */
 
 /* VIA/Cyrix/Centaur-defined CPU features, CPUID level 0xC0000001, word 5 */
 #define X86_FEATURE_XSTORE	(5*32+ 2) /* "rng" RNG present (xstore) */

@@ -237,6 +238,7 @@ extern const char * const x86_power_flags[32];
 #define cpu_has_xmm4_2		boot_cpu_has(X86_FEATURE_XMM4_2)
 #define cpu_has_x2apic		boot_cpu_has(X86_FEATURE_X2APIC)
 #define cpu_has_xsave		boot_cpu_has(X86_FEATURE_XSAVE)
+#define cpu_has_hypervisor	boot_cpu_has(X86_FEATURE_HYPERVISOR)
 
 #if defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_64)
 # define cpu_has_invlpg		1
include/asm-x86/processor.h +6 -0
index ee7cbb3..b09e2e6 100644
@@ -21,6 +21,7 @@ struct mm_struct;
 #include <asm/desc_defs.h>
 #include <asm/nops.h>
 #include <asm/ds.h>
+#include <asm/vmware.h>
 
 #include <linux/personality.h>
 #include <linux/cpumask.h>

@@ -110,6 +111,7 @@ struct cpuinfo_x86 {
 	/* Index into per_cpu list: */
 	u16			cpu_index;
 #endif
+	unsigned int		x86_hyper_vendor;
 } __attribute__((__aligned__(SMP_CACHE_BYTES)));
 
 #define X86_VENDOR_INTEL	0

@@ -123,6 +125,9 @@ struct cpuinfo_x86 {
 
 #define X86_VENDOR_UNKNOWN	0xff
 
+#define X86_HYPER_VENDOR_NONE	0
+#define X86_HYPER_VENDOR_VMWARE 1
+
 /*
  * capabilities of CPUs
  */

@@ -168,6 +173,7 @@ extern unsigned short num_cache_leaves;
 
 extern void detect_extended_topology(struct cpuinfo_x86 *c);
 extern void detect_ht(struct cpuinfo_x86 *c);
+extern void detect_hypervisor_vendor(struct cpuinfo_x86 *c);
 
 static inline void native_cpuid(unsigned int *eax, unsigned int *ebx,
 				unsigned int *ecx, unsigned int *edx)
include/asm-x86/vmware.h new file +26 -0
new file mode 100644
index 0000000..02dfea5
@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2008, VMware, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+#ifndef ASM_X86__VMWARE_H
+#define ASM_X86__VMWARE_H
+
+extern unsigned long vmware_get_tsc_khz(void);
+extern int vmware_platform(void);
+
+#endif