On Tue, Sep 03, 2013 at 11:30:23AM -0700, K. Y. Srinivasan wrote:
> 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 <o...@aepfle.de>, Jan Beulich
> <jbeul...@suse.com> and
> H. Peter Anvin <h.peter.an...@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 <k...@microsoft.com>
> ---
> arch/x86/include/uapi/asm/hyperv.h | 19 +++++++++++++++++++
> arch/x86/kernel/cpu/mshyperv.c | 24 ++++++++++++++++++++++++
> 2 files changed, 43 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/include/uapi/asm/hyperv.h
> b/arch/x86/include/uapi/asm/hyperv.h
> index b80420b..b8f1c01 100644
> --- a/arch/x86/include/uapi/asm/hyperv.h
> +++ b/arch/x86/include/uapi/asm/hyperv.h
> @@ -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
> +
You do not use this MSR in the patch, but in general how it suppose to
work during migration if host TSC frequency changes?
> +/* 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
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 71a39f3..b3dc639 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 /= 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);
> }
> --
> 1.7.4.1
>
> --
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Gleb.
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