From 88b094fb8d4fe43b7025ea8d487059e8813e02cd Mon Sep 17 00:00:00 2001 From: Alok Kataria Date: Mon, 27 Oct 2008 10:41:46 -0700 Subject: x86: Hypervisor detection and get tsc_freq from hypervisor Impact: Changes timebase calibration on Vmware. v3->v2 : Abstract the hypervisor detection and feature (tsc_freq) request behind a hypervisor.c file 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 function 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 hypervisor port to check if we are under VMware. The DMI + "VMware hypervisor port 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 hypervisor port should 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 hypervisor port if we are running on VMware. Other hypervisors too can add code to the generic routine to get frequency on their platform. Signed-off-by: Alok N Kataria Signed-off-by: Dan Hecht Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/hypervisor.c | 48 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 arch/x86/kernel/cpu/hypervisor.c (limited to 'arch/x86/kernel/cpu/hypervisor.c') diff --git a/arch/x86/kernel/cpu/hypervisor.c b/arch/x86/kernel/cpu/hypervisor.c new file mode 100644 index 00000000000..7bd55064ffe --- /dev/null +++ b/arch/x86/kernel/cpu/hypervisor.c @@ -0,0 +1,48 @@ +/* + * Common hypervisor code + * + * Copyright (C) 2008, VMware, Inc. + * Author : Alok N Kataria + * + * 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 +#include + +static inline 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; + } +} + +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; +} + +void __cpuinit init_hypervisor(struct cpuinfo_x86 *c) +{ + detect_hypervisor_vendor(c); +} + -- cgit v1.2.3-70-g09d2 From eca0cd028bdf0f6aaceb0d023e9c7501079a7dda Mon Sep 17 00:00:00 2001 From: Alok Kataria Date: Fri, 31 Oct 2008 12:01:58 -0700 Subject: x86: Add a synthetic TSC_RELIABLE feature bit. Impact: Changes timebase calibration on Vmware. Use the synthetic TSC_RELIABLE bit to workaround virtualization anomalies. Virtual TSCs can be kept nearly in sync, but because the virtual TSC offset is set by software, it's not perfect. So, the TSC synchronization test can fail. Even then the TSC can be used as a clocksource since the VMware platform exports a reliable TSC to the guest for timekeeping purposes. Use this bit to check if we need to skip the TSC sync checks. Along with this also set the CONSTANT_TSC bit when on VMware, since we still want to use TSC as clocksource on VM running over hardware which has unsynchronized TSC's (opteron's), since the hypervisor will take care of providing consistent TSC to the guest. Signed-off-by: Alok N Kataria Signed-off-by: Dan Hecht Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/vmware.h | 1 + arch/x86/kernel/cpu/hypervisor.c | 11 ++++++++++- arch/x86/kernel/cpu/vmware.c | 18 ++++++++++++++++++ arch/x86/kernel/tsc_sync.c | 8 +++++++- 4 files changed, 36 insertions(+), 2 deletions(-) (limited to 'arch/x86/kernel/cpu/hypervisor.c') diff --git a/arch/x86/include/asm/vmware.h b/arch/x86/include/asm/vmware.h index 02dfea5aebc..c11b7e100d8 100644 --- a/arch/x86/include/asm/vmware.h +++ b/arch/x86/include/asm/vmware.h @@ -22,5 +22,6 @@ extern unsigned long vmware_get_tsc_khz(void); extern int vmware_platform(void); +extern void vmware_set_feature_bits(struct cpuinfo_x86 *c); #endif diff --git a/arch/x86/kernel/cpu/hypervisor.c b/arch/x86/kernel/cpu/hypervisor.c index 7bd55064ffe..35ae2b75226 100644 --- a/arch/x86/kernel/cpu/hypervisor.c +++ b/arch/x86/kernel/cpu/hypervisor.c @@ -41,8 +41,17 @@ unsigned long get_hypervisor_tsc_freq(void) return 0; } +static inline void __cpuinit +hypervisor_set_feature_bits(struct cpuinfo_x86 *c) +{ + if (boot_cpu_data.x86_hyper_vendor == X86_HYPER_VENDOR_VMWARE) { + vmware_set_feature_bits(c); + return; + } +} + void __cpuinit init_hypervisor(struct cpuinfo_x86 *c) { detect_hypervisor_vendor(c); + hypervisor_set_feature_bits(c); } - diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c index d5d1b75a4b7..2ac4394fcb9 100644 --- a/arch/x86/kernel/cpu/vmware.c +++ b/arch/x86/kernel/cpu/vmware.c @@ -86,3 +86,21 @@ unsigned long vmware_get_tsc_khz(void) BUG_ON(!vmware_platform()); return __vmware_get_tsc_khz(); } + +/* + * VMware hypervisor takes care of exporting a reliable TSC to the guest. + * Still, due to timing difference when running on virtual cpus, the TSC can + * be marked as unstable in some cases. For example, the TSC sync check at + * bootup can fail due to a marginal offset between vcpus' TSCs (though the + * TSCs do not drift from each other). Also, the ACPI PM timer clocksource + * is not suitable as a watchdog when running on a hypervisor because the + * kernel may miss a wrap of the counter if the vcpu is descheduled for a + * long time. To skip these checks at runtime we set these capability bits, + * so that the kernel could just trust the hypervisor with providing a + * reliable virtual TSC that is suitable for timekeeping. + */ +void __cpuinit vmware_set_feature_bits(struct cpuinfo_x86 *c) +{ + set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC); + set_cpu_cap(c, X86_FEATURE_TSC_RELIABLE); +} diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c index 9ffb01c31c4..5977c40a138 100644 --- a/arch/x86/kernel/tsc_sync.c +++ b/arch/x86/kernel/tsc_sync.c @@ -108,6 +108,12 @@ void __cpuinit check_tsc_sync_source(int cpu) if (unsynchronized_tsc()) return; + if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) { + printk(KERN_INFO + "Skipping synchronization checks as TSC is reliable.\n"); + return; + } + printk(KERN_INFO "checking TSC synchronization [CPU#%d -> CPU#%d]:", smp_processor_id(), cpu); @@ -161,7 +167,7 @@ void __cpuinit check_tsc_sync_target(void) { int cpus = 2; - if (unsynchronized_tsc()) + if (unsynchronized_tsc() || boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) return; /* -- cgit v1.2.3-70-g09d2 From 4e42ebd57b2e727b28bf5f6068e95cd19b0e807b Mon Sep 17 00:00:00 2001 From: Hannes Eder Date: Fri, 21 Nov 2008 22:56:17 +0100 Subject: x86: hypervisor - fix sparse warnings Impact: fix sparse build warning Fix the following sparse warnings: arch/x86/kernel/cpu/hypervisor.c:37:15: warning: symbol 'get_hypervisor_tsc_freq' was not declared. Should it be static? arch/x86/kernel/cpu/hypervisor.c:53:16: warning: symbol 'init_hypervisor' was not declared. Should it be static? Signed-off-by: Hannes Eder Cc: "Alok N Kataria" Cc: "Dan Hecht" Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/hypervisor.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/kernel/cpu/hypervisor.c') diff --git a/arch/x86/kernel/cpu/hypervisor.c b/arch/x86/kernel/cpu/hypervisor.c index 35ae2b75226..fb5b86af0b0 100644 --- a/arch/x86/kernel/cpu/hypervisor.c +++ b/arch/x86/kernel/cpu/hypervisor.c @@ -23,6 +23,7 @@ #include #include +#include static inline void __cpuinit detect_hypervisor_vendor(struct cpuinfo_x86 *c) -- cgit v1.2.3-70-g09d2