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x86, hyperv: Get the local APIC timer frequency from the hypervisor

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Hyper-V supports a mechanism for retrieving the local APIC frequency.
Use this and bypass the calibration code in the kernel . This would
allow us to boot the Linux kernel as a "modern VM" on Hyper-V where
many of the legacy devices (such as PIT) are not emulated.

I would like to thank Olaf Hering <olaf@aepfle.de>, Jan Beulich <JBeulich@suse.com> and
H. Peter Anvin <h.peter.anvin@intel.com> for their help in this effort.

In this version of the patch, I have addressed Jan's comments.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Link: http://lkml.kernel.org/r/1380554932-9888-1-git-send-email-olaf@aepfle.de
Tested-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
K. Y. Srinivasan 2013-09-30 17:28:52 +02:00 committed by H. Peter Anvin
parent d0e639c9e0
commit 9e7827b5ea
2 changed files with 43 additions and 0 deletions
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19
arch/x86/include/uapi/asm/hyperv.h
View file

@ -27,6 +27,19 @@
#define HV_X64_MSR_VP_RUNTIME_AVAILABLE (1 << 0)
/* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
#define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE (1 << 1)
/*
* There is a single feature flag that signifies the presence of the MSR
* that can be used to retrieve both the local APIC Timer frequency as
* well as the TSC frequency.
*/
/* Local APIC timer frequency MSR (HV_X64_MSR_APIC_FREQUENCY) is available */
#define HV_X64_MSR_APIC_FREQUENCY_AVAILABLE (1 << 11)
/* TSC frequency MSR (HV_X64_MSR_TSC_FREQUENCY) is available */
#define HV_X64_MSR_TSC_FREQUENCY_AVAILABLE (1 << 11)
/*
* Basic SynIC MSRs (HV_X64_MSR_SCONTROL through HV_X64_MSR_EOM
* and HV_X64_MSR_SINT0 through HV_X64_MSR_SINT15) available
@ -136,6 +149,12 @@
/* MSR used to read the per-partition time reference counter */
#define HV_X64_MSR_TIME_REF_COUNT 0x40000020
/* MSR used to retrieve the TSC frequency */
#define HV_X64_MSR_TSC_FREQUENCY 0x40000022
/* MSR used to retrieve the local APIC timer frequency */
#define HV_X64_MSR_APIC_FREQUENCY 0x40000023
/* Define the virtual APIC registers */
#define HV_X64_MSR_EOI 0x40000070
#define HV_X64_MSR_ICR 0x40000071

24
arch/x86/kernel/cpu/mshyperv.c
View file

@ -15,6 +15,7 @@
#include <linux/clocksource.h>
#include <linux/module.h>
#include <linux/hardirq.h>
#include <linux/efi.h>
#include <linux/interrupt.h>
#include <asm/processor.h>
#include <asm/hypervisor.h>
@ -23,6 +24,7 @@
#include <asm/desc.h>
#include <asm/idle.h>
#include <asm/irq_regs.h>
#include <asm/i8259.h>
struct ms_hyperv_info ms_hyperv;
EXPORT_SYMBOL_GPL(ms_hyperv);
@ -67,6 +69,8 @@ static struct clocksource hyperv_cs = {
static void __init ms_hyperv_init_platform(void)
{
u64 hv_lapic_frequency;
/*
* Extract the features and hints
*/
@ -76,6 +80,26 @@ static void __init ms_hyperv_init_platform(void)
printk(KERN_INFO "HyperV: features 0x%x, hints 0x%x\n",
ms_hyperv.features, ms_hyperv.hints);
if (ms_hyperv.features & HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
/*
* Get the APIC frequency.
*/
rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
hv_lapic_frequency = div_u64(hv_lapic_frequency, HZ);
lapic_timer_frequency = hv_lapic_frequency;
printk(KERN_INFO "HyperV: LAPIC Timer Frequency: %#x\n",
lapic_timer_frequency);
/*
* On Hyper-V, when we are booting off an EFI firmware stack,
* we do not have many legacy devices including PIC, PIT etc.
*/
if (efi_enabled(EFI_BOOT)) {
printk(KERN_INFO "HyperV: Using null_legacy_pic\n");
legacy_pic = &null_legacy_pic;
}
}
if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
}