diff options
| author | K. Y. Srinivasan <kys@microsoft.com> | 2013-09-30 17:28:52 +0200 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2013-10-10 11:44:12 -0700 |
| commit | 9e7827b5ea4ca93b4d864bc07c0fafb838d496b1 (patch) | |
| tree | 6ceba20f6e2961e29dfdf42b02e1881cd629b94b /arch/x86/kernel/cpu/mshyperv.c | |
| parent | d0e639c9e06d44e713170031fe05fb60ebe680af (diff) | |
x86, hyperv: Get the local APIC timer frequency from the hypervisor
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>
Diffstat (limited to 'arch/x86/kernel/cpu/mshyperv.c')
| -rw-r--r-- | arch/x86/kernel/cpu/mshyperv.c | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 71a39f3621b..0a490ca278e 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -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); } |