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* [PATCH v3 0/2] Enable PV qspinlock for Hyper-V
@ 2018-09-27  6:01 Yi Sun
  2018-09-27  6:01 ` [PATCH v3 1/2] X86/Hyper-V: Add Guest IDLE MSR support Yi Sun
  2018-09-27  6:01 ` [PATCH v3 2/2] locking/pvqspinlock, hv: Enable PV qspinlock for Hyper-V Yi Sun
  0 siblings, 2 replies; 11+ messages in thread
From: Yi Sun @ 2018-09-27  6:01 UTC (permalink / raw)
  To: linux-kernel
  Cc: x86, tglx, chao.p.peng, chao.gao, isaku.yamahata,
	michael.h.kelley, tianyu.lan, Yi Sun, K. Y. Srinivasan,
	Haiyang Zhang, Stephen Hemminger, Jonathan Corbet,
	Michael Kelley (EOSG)

v2->v3:
    - use "Hyper-V: " as the message prefix
    - remove unnecessary header files
    - remove unnecessary check in 'hv_qlock_wait'
    - fix compilation error on different platforms

v1->v2:
    - compile hv_spinlock.c only when CONFIG_PARAVIRT_SPINLOCKS enabled
    - merge v1 patch 2/3 to single patch
    - remove part of the boilerplate in hv_spinlock.c
    - declare hv_pvspin as __initdata
    - remove spin_wait_info and hv_notify_long_spin_wait because
      SpinWaitInfo is a standalone feature.
    - add comments for reading HV_X64_MSR_GUEST_IDLE
    - replace pr_warn to pr_info
    - use pr_fmt instead of the 'hv:' prefix
    - register callback function for smp_ops.smp_prepare_boot_cpu
      to initialize hyper-v spinlock

This patch adds the necessary Hyper-V specific code to allow
PV qspinlock work on Hyper-V.

In wait callback function, read HV_X64_MSR_GUEST_IDLE MSR
to trigger the guest's transition to the idle power state
which can be exited by an IPI even if IF flag is disabled.

In kick callback function, just send platform IPI to make
waiting vcpu exit idle state.

In vcpu_is_preempted callback function, return false directly
because Hyper-V does not provide such interface so far.


Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Kelley (EOSG) <Michael.H.Kelley@microsoft.com>

Yi Sun (2):
  X86/Hyper-V: Add Guest IDLE MSR support
  locking/pvqspinlock, hv: Enable PV qspinlock for Hyper-V

 Documentation/admin-guide/kernel-parameters.txt |  5 ++
 arch/x86/hyperv/Makefile                        |  4 ++
 arch/x86/hyperv/hv_spinlock.c                   | 76 +++++++++++++++++++++++++
 arch/x86/include/asm/hyperv-tlfs.h              |  5 ++
 arch/x86/include/asm/mshyperv.h                 |  1 +
 arch/x86/kernel/cpu/mshyperv.c                  | 14 +++++
 6 files changed, 105 insertions(+)
 create mode 100644 arch/x86/hyperv/hv_spinlock.c

-- 
1.9.1


^ permalink raw reply	[flat|nested] 11+ messages in thread
* [PATCH v4 2/2] locking/pvqspinlock, hv: Enable PV qspinlock for Hyper-V
@ 2018-10-08  8:29 Yi Sun
  2018-10-09  9:30 ` [tip:x86/hyperv] x86/hyperv: " tip-bot for Yi Sun
  0 siblings, 1 reply; 11+ messages in thread
From: Yi Sun @ 2018-10-08  8:29 UTC (permalink / raw)
  To: linux-kernel
  Cc: x86, tglx, jgross, chao.p.peng, chao.gao, isaku.yamahata,
	michael.h.kelley, tianyu.lan, Yi Sun, K. Y. Srinivasan,
	Haiyang Zhang, Stephen Hemminger, Michael Kelley (EOSG)

Follow PV spinlock mechanism to implement the callback functions
to allow the CPU idling and kicking operations on Hyper-V.

Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Kelley (EOSG) <Michael.H.Kelley@microsoft.com>
Cc: Juergen Gross <jgross@suse.com>
Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
---
v3->v4:
    - To avoid possible hang issue (if hv_qlock_wait can be
      interrupted, kick may happen before reading HV_X64_MSR_GUEST_IDLE
      so that hang happens), disable interrupt before READ_ONCE, then
      restore it after reading HV_X64_MSR_GUEST_IDLE.
      (suggested by Juergen Gross)
---
 Documentation/admin-guide/kernel-parameters.txt |  5 ++
 arch/x86/hyperv/Makefile                        |  4 ++
 arch/x86/hyperv/hv_spinlock.c                   | 85 +++++++++++++++++++++++++
 arch/x86/include/asm/mshyperv.h                 |  1 +
 arch/x86/kernel/cpu/mshyperv.c                  | 14 ++++
 5 files changed, 109 insertions(+)
 create mode 100644 arch/x86/hyperv/hv_spinlock.c

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 92eb1f4..0fc8448 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1385,6 +1385,11 @@
 	hvc_iucv_allow=	[S390]	Comma-separated list of z/VM user IDs.
 				If specified, z/VM IUCV HVC accepts connections
 				from listed z/VM user IDs only.
+
+	hv_nopvspin	[X86,HYPER_V]
+			Disables the ticketlock slowpath using HYPER-V PV
+			optimizations.
+
 	keep_bootcon	[KNL]
 			Do not unregister boot console at start. This is only
 			useful for debugging when something happens in the window
diff --git a/arch/x86/hyperv/Makefile b/arch/x86/hyperv/Makefile
index b21ee65..1c11f94 100644
--- a/arch/x86/hyperv/Makefile
+++ b/arch/x86/hyperv/Makefile
@@ -1,2 +1,6 @@
 obj-y			:= hv_init.o mmu.o nested.o
 obj-$(CONFIG_X86_64)	+= hv_apic.o
+
+ifdef CONFIG_X86_64
+obj-$(CONFIG_PARAVIRT_SPINLOCKS)	+= hv_spinlock.o
+endif
diff --git a/arch/x86/hyperv/hv_spinlock.c b/arch/x86/hyperv/hv_spinlock.c
new file mode 100644
index 0000000..b628343
--- /dev/null
+++ b/arch/x86/hyperv/hv_spinlock.c
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Hyper-V specific spinlock code.
+ *
+ * Copyright (C) 2018, Intel, Inc.
+ *
+ * Author : Yi Sun <yi.y.sun@intel.com>
+ */
+
+#define pr_fmt(fmt) "Hyper-V: " fmt
+
+#include <linux/spinlock.h>
+
+#include <asm/mshyperv.h>
+#include <asm/hyperv-tlfs.h>
+#include <asm/paravirt.h>
+#include <asm/qspinlock.h>
+#include <asm/apic.h>
+
+static bool __initdata hv_pvspin = true;
+
+static void hv_qlock_kick(int cpu)
+{
+	apic->send_IPI(cpu, X86_PLATFORM_IPI_VECTOR);
+}
+
+static void hv_qlock_wait(u8 *byte, u8 val)
+{
+	unsigned long msr_val;
+	unsigned long flags;
+
+	if (in_nmi())
+		return;
+
+	local_irq_save(flags);
+
+	if (READ_ONCE(*byte) != val)
+		goto out;
+
+	/*
+	 * Read HV_X64_MSR_GUEST_IDLE MSR can trigger the guest's
+	 * transition to the idle power state which can be exited
+	 * by an IPI even if IF flag is disabled.
+	 */
+	rdmsrl(HV_X64_MSR_GUEST_IDLE, msr_val);
+
+out:
+	local_irq_restore(flags);
+}
+
+/*
+ * Hyper-V does not support this so far.
+ */
+bool hv_vcpu_is_preempted(int vcpu)
+{
+	return false;
+}
+PV_CALLEE_SAVE_REGS_THUNK(hv_vcpu_is_preempted);
+
+void __init hv_init_spinlocks(void)
+{
+	if (!hv_pvspin ||
+	    !apic ||
+	    !(ms_hyperv.hints & HV_X64_CLUSTER_IPI_RECOMMENDED) ||
+	    !(ms_hyperv.features & HV_X64_MSR_GUEST_IDLE_AVAILABLE)) {
+		pr_info("PV spinlocks disabled\n");
+		return;
+	}
+	pr_info("PV spinlocks enabled\n");
+
+	__pv_init_lock_hash();
+	pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
+	pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
+	pv_lock_ops.wait = hv_qlock_wait;
+	pv_lock_ops.kick = hv_qlock_kick;
+	pv_lock_ops.vcpu_is_preempted = PV_CALLEE_SAVE(hv_vcpu_is_preempted);
+}
+
+static __init int hv_parse_nopvspin(char *arg)
+{
+	hv_pvspin = false;
+	return 0;
+}
+early_param("hv_nopvspin", hv_parse_nopvspin);
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index f377044..759cfd2 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -351,6 +351,7 @@ static inline int cpumask_to_vpset(struct hv_vpset *vpset,
 
 #ifdef CONFIG_X86_64
 void hv_apic_init(void);
+void __init hv_init_spinlocks(void);
 #else
 static inline void hv_apic_init(void) {}
 #endif
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index ad12733..a5cc219 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -199,6 +199,16 @@ static unsigned long hv_get_tsc_khz(void)
 	return freq / 1000;
 }
 
+#if defined(CONFIG_SMP) && IS_ENABLED(CONFIG_HYPERV)
+static void __init hv_smp_prepare_boot_cpu(void)
+{
+	native_smp_prepare_boot_cpu();
+#if defined(CONFIG_X86_64) && defined(CONFIG_PARAVIRT_SPINLOCKS)
+	hv_init_spinlocks();
+#endif
+}
+#endif
+
 static void __init ms_hyperv_init_platform(void)
 {
 	int hv_host_info_eax;
@@ -303,6 +313,10 @@ static void __init ms_hyperv_init_platform(void)
 	if (ms_hyperv.misc_features & HV_STIMER_DIRECT_MODE_AVAILABLE)
 		alloc_intr_gate(HYPERV_STIMER0_VECTOR,
 				hv_stimer0_callback_vector);
+
+#if defined(CONFIG_SMP)
+	smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu;
+#endif
 #endif
 }
 
-- 
1.9.1


^ permalink raw reply related	[flat|nested] 11+ messages in thread
end of thread, other threads:[~2018-10-09 12:28 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-09-27  6:01 [PATCH v3 0/2] Enable PV qspinlock for Hyper-V Yi Sun
2018-09-27  6:01 ` [PATCH v3 1/2] X86/Hyper-V: Add Guest IDLE MSR support Yi Sun
2018-10-02 11:27   ` [tip:x86/hyperv] x86/hyperv: Add GUEST_IDLE_MSR support tip-bot for Yi Sun
2018-10-09 12:27   ` [tip:x86/paravirt] " tip-bot for Yi Sun
2018-09-27  6:01 ` [PATCH v3 2/2] locking/pvqspinlock, hv: Enable PV qspinlock for Hyper-V Yi Sun
2018-09-28 22:09   ` Michael Kelley (EOSG)
2018-10-02 11:28   ` [tip:x86/hyperv] x86/hyperv: " tip-bot for Yi Sun
2018-10-02 11:38     ` Juergen Gross
2018-10-02 12:13       ` Thomas Gleixner
2018-10-08  8:12       ` Yi Sun
2018-10-08  8:29 [PATCH v4 2/2] locking/pvqspinlock, hv: " Yi Sun
2018-10-09  9:30 ` [tip:x86/hyperv] x86/hyperv: " tip-bot for Yi Sun

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