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Commit 93286261 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Thomas Gleixner
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x86/hyperv: Reenlightenment notifications support 



Hyper-V supports Live Migration notification. This is supposed to be used
in conjunction with TSC emulation: when a VM is migrated to a host with
different TSC frequency for some short period the host emulates the
accesses to TSC and sends an interrupt to notify about the event. When the
guest is done updating everything it can disable TSC emulation and
everything will start working fast again.

These notifications weren't required until now as Hyper-V guests are not
supposed to use TSC as a clocksource: in Linux the TSC is even marked as
unstable on boot. Guests normally use 'tsc page' clocksource and host
updates its values on migrations automatically.

Things change when with nested virtualization: even when the PV
clocksources (kvm-clock or tsc page) are passed through to the nested
guests the TSC frequency and frequency changes need to be know..

Hyper-V Top Level Functional Specification (as of v5.0b) wrongly specifies
EAX:BIT(12) of CPUID:0x40000009 as the feature identification bit. The
right one to check is EAX:BIT(13) of CPUID:0x40000003. I was assured that
the fix in on the way.

Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>
Cc: Roman Kagan <rkagan@virtuozzo.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: devel@linuxdriverproject.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Cathy Avery <cavery@redhat.com>
Cc: Mohammed Gamal <mmorsy@redhat.com>
Link: https://lkml.kernel.org/r/20180124132337.30138-4-vkuznets@redhat.com
parent e2768eaa

arch/x86/entry/entry_32.S

+3 −0
Original line number Diff line number Diff line
@@ -895,6 +895,9 @@ BUILD_INTERRUPT3(xen_hvm_callback_vector, HYPERVISOR_CALLBACK_VECTOR, 
BUILD_INTERRUPT3(hyperv_callback_vector, HYPERVISOR_CALLBACK_VECTOR,

		 hyperv_vector_handler)



BUILD_INTERRUPT3(hyperv_reenlightenment_vector, HYPERV_REENLIGHTENMENT_VECTOR,

		 hyperv_reenlightenment_intr)



#endif /* CONFIG_HYPERV */



ENTRY(page_fault)

arch/x86/entry/entry_64.S

+3 −0
Original line number Diff line number Diff line
@@ -1245,6 +1245,9 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ 
#if IS_ENABLED(CONFIG_HYPERV)

apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \

	hyperv_callback_vector hyperv_vector_handler



apicinterrupt3 HYPERV_REENLIGHTENMENT_VECTOR \

	hyperv_reenlightenment_vector hyperv_reenlightenment_intr

#endif /* CONFIG_HYPERV */



idtentry debug			do_debug		has_error_code=0	paranoid=1 shift_ist=DEBUG_STACK

arch/x86/hyperv/hv_init.c

+89 −0
Original line number Diff line number Diff line
@@ -18,6 +18,8 @@ 
 */



#include <linux/types.h>

#include <asm/apic.h>

#include <asm/desc.h>

#include <asm/hypervisor.h>

#include <asm/hyperv.h>

#include <asm/mshyperv.h>
@@ -102,6 +104,93 @@ static int hv_cpu_init(unsigned int cpu) 
	return 0;

}



static void (*hv_reenlightenment_cb)(void);



static void hv_reenlightenment_notify(struct work_struct *dummy)

{

	struct hv_tsc_emulation_status emu_status;



	rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);



	/* Don't issue the callback if TSC accesses are not emulated */

	if (hv_reenlightenment_cb && emu_status.inprogress)

		hv_reenlightenment_cb();

}

static DECLARE_DELAYED_WORK(hv_reenlightenment_work, hv_reenlightenment_notify);



void hyperv_stop_tsc_emulation(void)

{

	u64 freq;

	struct hv_tsc_emulation_status emu_status;



	rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);

	emu_status.inprogress = 0;

	wrmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);



	rdmsrl(HV_X64_MSR_TSC_FREQUENCY, freq);

	tsc_khz = div64_u64(freq, 1000);

}

EXPORT_SYMBOL_GPL(hyperv_stop_tsc_emulation);



static inline bool hv_reenlightenment_available(void)

{

	/*

	 * Check for required features and priviliges to make TSC frequency

	 * change notifications work.

	 */

	return ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS &&

		ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE &&

		ms_hyperv.features & HV_X64_ACCESS_REENLIGHTENMENT;

}



__visible void __irq_entry hyperv_reenlightenment_intr(struct pt_regs *regs)

{

	entering_ack_irq();



	schedule_delayed_work(&hv_reenlightenment_work, HZ/10);



	exiting_irq();

}



void set_hv_tscchange_cb(void (*cb)(void))

{

	struct hv_reenlightenment_control re_ctrl = {

		.vector = HYPERV_REENLIGHTENMENT_VECTOR,

		.enabled = 1,

		.target_vp = hv_vp_index[smp_processor_id()]

	};

	struct hv_tsc_emulation_control emu_ctrl = {.enabled = 1};



	if (!hv_reenlightenment_available()) {

		pr_warn("Hyper-V: reenlightenment support is unavailable\n");

		return;

	}



	hv_reenlightenment_cb = cb;



	/* Make sure callback is registered before we write to MSRs */

	wmb();



	wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));

	wrmsrl(HV_X64_MSR_TSC_EMULATION_CONTROL, *((u64 *)&emu_ctrl));

}

EXPORT_SYMBOL_GPL(set_hv_tscchange_cb);



void clear_hv_tscchange_cb(void)

{

	struct hv_reenlightenment_control re_ctrl;



	if (!hv_reenlightenment_available())

		return;



	rdmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *(u64 *)&re_ctrl);

	re_ctrl.enabled = 0;

	wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *(u64 *)&re_ctrl);



	hv_reenlightenment_cb = NULL;

}

EXPORT_SYMBOL_GPL(clear_hv_tscchange_cb);



/*

 * This function is to be invoked early in the boot sequence after the

 * hypervisor has been detected.

arch/x86/include/asm/irq_vectors.h

+6 −1
Original line number Diff line number Diff line
@@ -103,7 +103,12 @@ 
#endif



#define MANAGED_IRQ_SHUTDOWN_VECTOR	0xef

#define LOCAL_TIMER_VECTOR		0xee



#if IS_ENABLED(CONFIG_HYPERV)

#define HYPERV_REENLIGHTENMENT_VECTOR	0xee

#endif



#define LOCAL_TIMER_VECTOR		0xed



#define NR_VECTORS			 256

arch/x86/include/asm/mshyperv.h

+9 −0
Original line number Diff line number Diff line
@@ -160,6 +160,7 @@ static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type) 
#define hv_set_synint_state(int_num, val) wrmsrl(int_num, val)



void hyperv_callback_vector(void);

void hyperv_reenlightenment_vector(void);

#ifdef CONFIG_TRACING

#define trace_hyperv_callback_vector hyperv_callback_vector

#endif
@@ -316,11 +317,19 @@ void hyper_alloc_mmu(void); 
void hyperv_report_panic(struct pt_regs *regs, long err);

bool hv_is_hypercall_page_setup(void);

void hyperv_cleanup(void);



void hyperv_reenlightenment_intr(struct pt_regs *regs);

void set_hv_tscchange_cb(void (*cb)(void));

void clear_hv_tscchange_cb(void);

void hyperv_stop_tsc_emulation(void);

#else /* CONFIG_HYPERV */

static inline void hyperv_init(void) {}

static inline bool hv_is_hypercall_page_setup(void) { return false; }

static inline void hyperv_cleanup(void) {}

static inline void hyperv_setup_mmu_ops(void) {}

static inline void set_hv_tscchange_cb(void (*cb)(void)) {}

static inline void clear_hv_tscchange_cb(void) {}

static inline void hyperv_stop_tsc_emulation(void) {};

#endif /* CONFIG_HYPERV */



#ifdef CONFIG_HYPERV_TSCPAGE