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

From: Alok Kataria
Date: Wed Oct 22 2008 - 15:22:54 EST

Hi hpa,
below is the v2 of this patch.

--

x86: Get TSC frequency from VMware hypervisor.

From: Alok N Kataria <akataria@xxxxxxxxxx>

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 <akataria@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
---

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


diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 01dc4c7..bca729b 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -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
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index ff26d87..a48cb0e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -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
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 343f3a9..b6b11f9 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -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
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 161bb85..4ae207c 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -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);
diff --git a/arch/x86/kernel/vmware.c b/arch/x86/kernel/vmware.c
new file mode 100644
index 0000000..650de86
--- /dev/null
+++ b/arch/x86/kernel/vmware.c
@@ -0,0 +1,87 @@
+/*
+ * VMware Detection code.
+ *
+ * Copyright (C) 2008, VMware, Inc.
+ * Author : Alok N Kataria <akataria@xxxxxxxxxx>
+ *
+ * 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.
+ *
+ */
+
+#include <linux/dmi.h>
+#include <asm/div64.h>
+
+#define CPUID_VMWARE_INFO_LEAF 0x40000000
+#define VMWARE_BDOOR_MAGIC 0x564D5868
+#define VMWARE_BDOOR_PORT 0x5658
+
+#define VMWARE_BDOOR_CMD_GETVERSION 10
+#define VMWARE_BDOOR_CMD_GETHZ 45
+
+#define VMWARE_BDOOR(cmd, eax, ebx, ecx, edx) \
+ __asm__("inl (%%dx)" : \
+ "=a"(eax), "=c"(ecx), "=d"(edx), "=b"(ebx) : \
+ "0"(VMWARE_BDOOR_MAGIC), "1"(VMWARE_BDOOR_CMD_##cmd), \
+ "2"(VMWARE_BDOOR_PORT), "3"(0) : \
+ "memory");
+
+static inline int __vmware_platform(void)
+{
+ uint32_t eax, ebx, ecx, edx;
+ VMWARE_BDOOR(GETVERSION, eax, ebx, ecx, edx);
+ return eax != (uint32_t)-1 && ebx == VMWARE_BDOOR_MAGIC;
+}
+
+static unsigned long __vmware_get_tsc_khz(void)
+{
+ uint64_t tsc_hz;
+ uint32_t eax, ebx, ecx, edx;
+
+ VMWARE_BDOOR(GETHZ, eax, ebx, ecx, edx);
+
+ if (eax == (uint32_t)-1)
+ return 0;
+ tsc_hz = eax | (((uint64_t)ebx) << 32);
+ do_div(tsc_hz, 1000);
+ BUG_ON(tsc_hz >> 32);
+ return tsc_hz;
+}
+
+int vmware_platform(void)
+{
+ if (cpu_has_hypervisor) {
+ unsigned int eax, ebx, ecx, edx;
+ char hyper_vendor_id[13];
+
+ cpuid(CPUID_VMWARE_INFO_LEAF, &eax, &ebx, &ecx, &edx);
+ memcpy(hyper_vendor_id + 0, &ebx, 4);
+ memcpy(hyper_vendor_id + 4, &ecx, 4);
+ memcpy(hyper_vendor_id + 8, &edx, 4);
+ hyper_vendor_id[12] = '\0';
+ if (!strcmp(hyper_vendor_id, "VMwareVMware"))
+ return 1;
+ } else if (dmi_available && dmi_name_in_vendors("VMware") &&
+ __vmware_platform())
+ return 1;
+
+ return 0;
+}
+
+unsigned long vmware_get_tsc_khz(void)
+{
+ BUG_ON(!vmware_platform());
+ return __vmware_get_tsc_khz();
+}
diff --git a/include/asm-x86/cpufeature.h b/include/asm-x86/cpufeature.h
index adfeae6..f891dfc 100644
--- a/include/asm-x86/cpufeature.h
+++ b/include/asm-x86/cpufeature.h
@@ -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
diff --git a/include/asm-x86/processor.h b/include/asm-x86/processor.h
index ee7cbb3..b09e2e6 100644
--- a/include/asm-x86/processor.h
+++ b/include/asm-x86/processor.h
@@ -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)
diff --git a/include/asm-x86/vmware.h b/include/asm-x86/vmware.h
new file mode 100644
index 0000000..02dfea5
--- /dev/null
+++ b/include/asm-x86/vmware.h
@@ -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


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