[PATCH v3 0/4] Add a unified parameter "nopvspin"

[PATCH v3 0/4] Add a unified parameter "nopvspin"

[Zhenzhong Duan]

There are cases folks want to disable spinlock optimization for
debug/test purpose. Xen and hyperv already have parameters "xen_nopvspin"
and "hv_nopvspin" to support that, but kvm doesn't.

The first patch adds that feature to KVM guest with "nopvspin".

For compatibility reason original parameters "xen_nopvspin" and
"hv_nopvspin" are retained and marked obsolete.

v3:
PATCH2: Fix indentation

v2:
PATCH1: pick the print code change into separate PATCH2,
        updated patch description             [Vitaly Kuznetsov]
PATCH2: new patch with print code change      [Vitaly Kuznetsov]
PATCH3: add Reviewed-by                       [Juergen Gross]

Thanks
Zhenzhong

[PATCH v3 1/4] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks

[Zhenzhong Duan]

There are cases where a guest tries to switch spinlocks to bare metal
behavior (e.g. by setting "xen_nopvspin" on XEN platform and
"hv_nopvspin" on HYPER_V).

That feature is missed on KVM, add a new parameter "nopvspin" to disable
PV spinlocks for KVM guest.

This new parameter is also used to replace "xen_nopvspin" and
"hv_nopvspin".

The global variable pvspin isn't defined as __initdata as it's used at
runtime by XEN guest.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
---
 Documentation/admin-guide/kernel-parameters.txt | 4 ++++
 arch/x86/include/asm/qspinlock.h                | 1 +
 arch/x86/kernel/kvm.c                           | 7 +++++++
 kernel/locking/qspinlock.c                      | 7 +++++++
 4 files changed, 19 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c7ac2f3..4b956d8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5330,6 +5330,10 @@
 			as generic guest with no PV drivers. Currently support
 			XEN HVM, KVM, HYPER_V and VMWARE guest.
 
+	nopvspin	[X86,KVM] Disables the qspinlock slow path
+			using PV optimizations which allow the hypervisor to
+			'idle' the guest on lock contention.
+
 	xirc2ps_cs=	[NET,PCMCIA]
 			Format:
 			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
index 444d6fd..34a4484 100644
--- a/arch/x86/include/asm/qspinlock.h
+++ b/arch/x86/include/asm/qspinlock.h
@@ -32,6 +32,7 @@ static __always_inline u32 queued_fetch_set_pending_acquire(struct qspinlock *lo
 extern void __pv_init_lock_hash(void);
 extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
 extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock);
+extern bool pvspin;
 
 #define	queued_spin_unlock queued_spin_unlock
 /**
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index e820568..a4f108d 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -842,6 +842,13 @@ void __init kvm_spinlock_init(void)
 	if (num_possible_cpus() == 1)
 		return;
 
+	if (!pvspin) {
+		pr_info("PV spinlocks disabled\n");
+		static_branch_disable(&virt_spin_lock_key);
+		return;
+	}
+	pr_info("PV spinlocks enabled\n");
+
 	__pv_init_lock_hash();
 	pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
 	pv_ops.lock.queued_spin_unlock =
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 2473f10..945b510 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -580,4 +580,11 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
 #include "qspinlock_paravirt.h"
 #include "qspinlock.c"
 
+bool pvspin = true;
+static __init int parse_nopvspin(char *arg)
+{
+	pvspin = false;
+	return 0;
+}
+early_param("nopvspin", parse_nopvspin);
 #endif
-- 
1.8.3.1

[PATCH v3 2/4] x86/kvm: Change print code to use pr_*() format

[Zhenzhong Duan]

pr_*() is preferred than printk(KERN_* ...), after change all the print
in arch/x86/kernel/kvm.c will have "KVM: xxx" style.

No functional change.

Suggested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
 arch/x86/kernel/kvm.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index a4f108d..ce4f578 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -7,6 +7,8 @@
  *   Authors: Anthony Liguori <aliguori@us.ibm.com>
  */
 
+#define pr_fmt(fmt) "KVM: " fmt
+
 #include <linux/context_tracking.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -286,8 +288,8 @@ static void kvm_register_steal_time(void)
 		return;
 
 	wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
-	pr_info("kvm-stealtime: cpu %d, msr %llx\n",
-		cpu, (unsigned long long) slow_virt_to_phys(st));
+	pr_info("stealtime: cpu %d, msr %llx\n", cpu,
+		(unsigned long long) slow_virt_to_phys(st));
 }
 
 static DEFINE_PER_CPU_DECRYPTED(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
@@ -321,8 +323,7 @@ static void kvm_guest_cpu_init(void)
 
 		wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);
 		__this_cpu_write(apf_reason.enabled, 1);
-		printk(KERN_INFO"KVM setup async PF for cpu %d\n",
-		       smp_processor_id());
+		pr_info("setup async PF for cpu %d\n", smp_processor_id());
 	}
 
 	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
@@ -347,8 +348,7 @@ static void kvm_pv_disable_apf(void)
 	wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
 	__this_cpu_write(apf_reason.enabled, 0);
 
-	printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
-	       smp_processor_id());
+	pr_info("Unregister pv shared memory for cpu %d\n", smp_processor_id());
 }
 
 static void kvm_pv_guest_cpu_reboot(void *unused)
@@ -509,7 +509,7 @@ static void kvm_setup_pv_ipi(void)
 {
 	apic->send_IPI_mask = kvm_send_ipi_mask;
 	apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
-	pr_info("KVM setup pv IPIs\n");
+	pr_info("setup pv IPIs\n");
 }
 
 static void kvm_smp_send_call_func_ipi(const struct cpumask *mask)
@@ -639,11 +639,11 @@ static void __init kvm_guest_init(void)
 	    !kvm_para_has_hint(KVM_HINTS_REALTIME) &&
 	    kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
 		smp_ops.send_call_func_ipi = kvm_smp_send_call_func_ipi;
-		pr_info("KVM setup pv sched yield\n");
+		pr_info("setup pv sched yield\n");
 	}
 	if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online",
 				      kvm_cpu_online, kvm_cpu_down_prepare) < 0)
-		pr_err("kvm_guest: Failed to install cpu hotplug callbacks\n");
+		pr_err("failed to install cpu hotplug callbacks\n");
 #else
 	sev_map_percpu_data();
 	kvm_guest_cpu_init();
@@ -746,7 +746,7 @@ static __init int kvm_setup_pv_tlb_flush(void)
 			zalloc_cpumask_var_node(per_cpu_ptr(&__pv_tlb_mask, cpu),
 				GFP_KERNEL, cpu_to_node(cpu));
 		}
-		pr_info("KVM setup pv remote TLB flush\n");
+		pr_info("setup pv remote TLB flush\n");
 	}
 
 	return 0;
@@ -879,8 +879,8 @@ static void kvm_enable_host_haltpoll(void *i)
 void arch_haltpoll_enable(unsigned int cpu)
 {
 	if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) {
-		pr_err_once("kvm: host does not support poll control\n");
-		pr_err_once("kvm: host upgrade recommended\n");
+		pr_err_once("host does not support poll control\n");
+		pr_err_once("host upgrade recommended\n");
 		return;
 	}
 
-- 
1.8.3.1

[PATCH v3 3/4] xen: Mark "xen_nopvspin" parameter obsolete and map it to "nopvspin"

[Zhenzhong Duan]

Fix stale description of "xen_nopvspin" as we use qspinlock now.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  7 ++++---
 arch/x86/xen/spinlock.c                         | 13 +++++++------
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 4b956d8..1f0a62f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5303,8 +5303,9 @@
 			never -- do not unplug even if version check succeeds
 
 	xen_nopvspin	[X86,XEN]
-			Disables the ticketlock slowpath using Xen PV
-			optimizations.
+			Disables the qspinlock slowpath using Xen PV optimizations.
+			This parameter is obsoleted by "nopvspin" parameter, which
+			has equivalent effect for XEN platform.
 
 	xen_nopv	[X86]
 			Disables the PV optimizations forcing the HVM guest to
@@ -5330,7 +5331,7 @@
 			as generic guest with no PV drivers. Currently support
 			XEN HVM, KVM, HYPER_V and VMWARE guest.
 
-	nopvspin	[X86,KVM] Disables the qspinlock slow path
+	nopvspin	[X86,XEN,KVM] Disables the qspinlock slow path
 			using PV optimizations which allow the hypervisor to
 			'idle' the guest on lock contention.
 
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 6deb490..092a53f 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -18,7 +18,6 @@
 static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
 static DEFINE_PER_CPU(char *, irq_name);
 static DEFINE_PER_CPU(atomic_t, xen_qlock_wait_nest);
-static bool xen_pvspin = true;
 
 static void xen_qlock_kick(int cpu)
 {
@@ -68,7 +67,7 @@ void xen_init_lock_cpu(int cpu)
 	int irq;
 	char *name;
 
-	if (!xen_pvspin)
+	if (!pvspin)
 		return;
 
 	WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
@@ -93,7 +92,7 @@ void xen_init_lock_cpu(int cpu)
 
 void xen_uninit_lock_cpu(int cpu)
 {
-	if (!xen_pvspin)
+	if (!pvspin)
 		return;
 
 	unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
@@ -117,9 +116,9 @@ void __init xen_init_spinlocks(void)
 
 	/*  Don't need to use pvqspinlock code if there is only 1 vCPU. */
 	if (num_possible_cpus() == 1)
-		xen_pvspin = false;
+		pvspin = false;
 
-	if (!xen_pvspin) {
+	if (!pvspin) {
 		printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
 		static_branch_disable(&virt_spin_lock_key);
 		return;
@@ -137,7 +136,9 @@ void __init xen_init_spinlocks(void)
 
 static __init int xen_parse_nopvspin(char *arg)
 {
-	xen_pvspin = false;
+	pr_notice("\"xen_nopvspin\" is deprecated, please use \"nopvspin\" instead\n");
+	if (xen_domain())
+		pvspin = false;
 	return 0;
 }
 early_param("xen_nopvspin", xen_parse_nopvspin);
-- 
1.8.3.1

[PATCH v3 4/4] x86/hyperv: Mark "hv_nopvspin" parameter obsolete and map it to "nopvspin"

[Zhenzhong Duan]

Includes asm/hypervisor.h in order to reference x86_hyper_type.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 6 +++++-
 arch/x86/hyperv/hv_spinlock.c                   | 9 +++++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1f0a62f..43f922c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1436,6 +1436,10 @@
 	hv_nopvspin	[X86,HYPER_V] Disables the paravirt spinlock optimizations
 				      which allow the hypervisor to 'idle' the
 				      guest on lock contention.
+				      This parameter is obsoleted by "nopvspin"
+				      parameter, which has equivalent effect for
+				      HYPER_V platform.
+
 
 	keep_bootcon	[KNL]
 			Do not unregister boot console at start. This is only
@@ -5331,7 +5335,7 @@
 			as generic guest with no PV drivers. Currently support
 			XEN HVM, KVM, HYPER_V and VMWARE guest.
 
-	nopvspin	[X86,XEN,KVM] Disables the qspinlock slow path
+	nopvspin	[X86,XEN,KVM,HYPER_V] Disables the qspinlock slow path
 			using PV optimizations which allow the hypervisor to
 			'idle' the guest on lock contention.
 
diff --git a/arch/x86/hyperv/hv_spinlock.c b/arch/x86/hyperv/hv_spinlock.c
index 07f21a0..e00e319 100644
--- a/arch/x86/hyperv/hv_spinlock.c
+++ b/arch/x86/hyperv/hv_spinlock.c
@@ -12,12 +12,11 @@
 
 #include <linux/spinlock.h>
 
+#include <asm/hypervisor.h>
 #include <asm/mshyperv.h>
 #include <asm/paravirt.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);
@@ -64,7 +63,7 @@ __visible bool hv_vcpu_is_preempted(int vcpu)
 
 void __init hv_init_spinlocks(void)
 {
-	if (!hv_pvspin || !apic ||
+	if (!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");
@@ -82,7 +81,9 @@ void __init hv_init_spinlocks(void)
 
 static __init int hv_parse_nopvspin(char *arg)
 {
-	hv_pvspin = false;
+	pr_notice("\"hv_nopvspin\" is deprecated, please use \"nopvspin\" instead\n");
+	if (x86_hyper_type == X86_HYPER_MS_HYPERV)
+		pvspin = false;
 	return 0;
 }
 early_param("hv_nopvspin", hv_parse_nopvspin);
-- 
1.8.3.1

Re: [PATCH v3 1/4] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks

[Sean Christopherson]

On Mon, Sep 30, 2019 at 08:44:36PM +0800, Zhenzhong Duan wrote:
> There are cases where a guest tries to switch spinlocks to bare metal
> behavior (e.g. by setting "xen_nopvspin" on XEN platform and
> "hv_nopvspin" on HYPER_V).
> 
> That feature is missed on KVM, add a new parameter "nopvspin" to disable
> PV spinlocks for KVM guest.
> 
> This new parameter is also used to replace "xen_nopvspin" and
> "hv_nopvspin".

This is confusing as there are no Xen or Hyper-V changes in this patch.
Please make it clear that you're talking about future patches, e.g.:

  The new 'nopvspin' parameter will also replace Xen and Hyper-V specific
  parameters in future patches.

> 
> The global variable pvspin isn't defined as __initdata as it's used at
> runtime by XEN guest.

Same comment as above regarding what this patch is doing versus what will
be done in the future.  Arguably you should even mark it __initdata in
this patch and deal with conflict in the Xen patch, e.g. use it only to
set the existing xen_pvspin variable.

> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krcmar <rkrcmar@redhat.com>
> Cc: Sean Christopherson <sean.j.christopherson@intel.com>
> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> Cc: Wanpeng Li <wanpengli@tencent.com>
> Cc: Jim Mattson <jmattson@google.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Will Deacon <will@kernel.org>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 4 ++++
>  arch/x86/include/asm/qspinlock.h                | 1 +
>  arch/x86/kernel/kvm.c                           | 7 +++++++
>  kernel/locking/qspinlock.c                      | 7 +++++++
>  4 files changed, 19 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index c7ac2f3..4b956d8 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -5330,6 +5330,10 @@
>  			as generic guest with no PV drivers. Currently support
>  			XEN HVM, KVM, HYPER_V and VMWARE guest.
>  
> +	nopvspin	[X86,KVM] Disables the qspinlock slow path
> +			using PV optimizations which allow the hypervisor to
> +			'idle' the guest on lock contention.
> +
>  	xirc2ps_cs=	[NET,PCMCIA]
>  			Format:
>  			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
> diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
> index 444d6fd..34a4484 100644
> --- a/arch/x86/include/asm/qspinlock.h
> +++ b/arch/x86/include/asm/qspinlock.h
> @@ -32,6 +32,7 @@ static __always_inline u32 queued_fetch_set_pending_acquire(struct qspinlock *lo
>  extern void __pv_init_lock_hash(void);
>  extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
>  extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock);
> +extern bool pvspin;
>  
>  #define	queued_spin_unlock queued_spin_unlock
>  /**
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index e820568..a4f108d 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -842,6 +842,13 @@ void __init kvm_spinlock_init(void)
>  	if (num_possible_cpus() == 1)
>  		return;
>  
> +	if (!pvspin) {
> +		pr_info("PV spinlocks disabled\n");
> +		static_branch_disable(&virt_spin_lock_key);
> +		return;
> +	}
> +	pr_info("PV spinlocks enabled\n");

These prints could be confusing as KVM also disables PV spinlocks when it
sees KVM_HINTS_REALTIME.

> +
>  	__pv_init_lock_hash();
>  	pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
>  	pv_ops.lock.queued_spin_unlock =
> diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
> index 2473f10..945b510 100644
> --- a/kernel/locking/qspinlock.c
> +++ b/kernel/locking/qspinlock.c
> @@ -580,4 +580,11 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
>  #include "qspinlock_paravirt.h"
>  #include "qspinlock.c"
>  
> +bool pvspin = true;

This can be __ro_after_init, or probably better __initdata and have Xen
snapshot the value for its use case.

Personal preference: I'd invert the bool and name it nopvspin to make it
easier to connect the variable to the kernel param.

> +static __init int parse_nopvspin(char *arg)
> +{
> +	pvspin = false;
> +	return 0;
> +}
> +early_param("nopvspin", parse_nopvspin);
>  #endif
> -- 
> 1.8.3.1
> 

Re: [PATCH v3 2/4] x86/kvm: Change print code to use pr_*() format

[Sean Christopherson]

On Mon, Sep 30, 2019 at 08:44:37PM +0800, Zhenzhong Duan wrote:
> pr_*() is preferred than printk(KERN_* ...), after change all the print
> in arch/x86/kernel/kvm.c will have "KVM: xxx" style.
> 
> No functional change.
> 
> Suggested-by: Vitaly Kuznetsov <vkuznets@redhat.com>

This wasn't really suggested by Vitaly, he just requested it be done in a
separate patch.

> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krcmar <rkrcmar@redhat.com>
> Cc: Sean Christopherson <sean.j.christopherson@intel.com>
> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> Cc: Wanpeng Li <wanpengli@tencent.com>
> Cc: Jim Mattson <jmattson@google.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> ---
>  arch/x86/kernel/kvm.c | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index a4f108d..ce4f578 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -7,6 +7,8 @@
>   *   Authors: Anthony Liguori <aliguori@us.ibm.com>
>   */
>  
> +#define pr_fmt(fmt) "KVM: " fmt

Not a fan of "KVM" as the prefix as it's easily confused with KVM the
hypervisor.  Maybe "kvm_guest"?

> +
>  #include <linux/context_tracking.h>
>  #include <linux/init.h>
>  #include <linux/kernel.h>
> @@ -286,8 +288,8 @@ static void kvm_register_steal_time(void)
>  		return;
>  
>  	wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
> -	pr_info("kvm-stealtime: cpu %d, msr %llx\n",
> -		cpu, (unsigned long long) slow_virt_to_phys(st));
> +	pr_info("stealtime: cpu %d, msr %llx\n", cpu,
> +		(unsigned long long) slow_virt_to_phys(st));
>  }
>  
>  static DEFINE_PER_CPU_DECRYPTED(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
> @@ -321,8 +323,7 @@ static void kvm_guest_cpu_init(void)
>  
>  		wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);
>  		__this_cpu_write(apf_reason.enabled, 1);
> -		printk(KERN_INFO"KVM setup async PF for cpu %d\n",
> -		       smp_processor_id());
> +		pr_info("setup async PF for cpu %d\n", smp_processor_id());
>  	}
>  
>  	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
> @@ -347,8 +348,7 @@ static void kvm_pv_disable_apf(void)
>  	wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
>  	__this_cpu_write(apf_reason.enabled, 0);
>  
> -	printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
> -	       smp_processor_id());
> +	pr_info("Unregister pv shared memory for cpu %d\n", smp_processor_id());
>  }
>  
>  static void kvm_pv_guest_cpu_reboot(void *unused)
> @@ -509,7 +509,7 @@ static void kvm_setup_pv_ipi(void)
>  {
>  	apic->send_IPI_mask = kvm_send_ipi_mask;
>  	apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
> -	pr_info("KVM setup pv IPIs\n");
> +	pr_info("setup pv IPIs\n");
>  }
>  
>  static void kvm_smp_send_call_func_ipi(const struct cpumask *mask)
> @@ -639,11 +639,11 @@ static void __init kvm_guest_init(void)
>  	    !kvm_para_has_hint(KVM_HINTS_REALTIME) &&
>  	    kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
>  		smp_ops.send_call_func_ipi = kvm_smp_send_call_func_ipi;
> -		pr_info("KVM setup pv sched yield\n");
> +		pr_info("setup pv sched yield\n");
>  	}
>  	if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online",
>  				      kvm_cpu_online, kvm_cpu_down_prepare) < 0)
> -		pr_err("kvm_guest: Failed to install cpu hotplug callbacks\n");
> +		pr_err("failed to install cpu hotplug callbacks\n");
>  #else
>  	sev_map_percpu_data();
>  	kvm_guest_cpu_init();
> @@ -746,7 +746,7 @@ static __init int kvm_setup_pv_tlb_flush(void)
>  			zalloc_cpumask_var_node(per_cpu_ptr(&__pv_tlb_mask, cpu),
>  				GFP_KERNEL, cpu_to_node(cpu));
>  		}
> -		pr_info("KVM setup pv remote TLB flush\n");
> +		pr_info("setup pv remote TLB flush\n");
>  	}
>  
>  	return 0;
> @@ -879,8 +879,8 @@ static void kvm_enable_host_haltpoll(void *i)
>  void arch_haltpoll_enable(unsigned int cpu)
>  {
>  	if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) {
> -		pr_err_once("kvm: host does not support poll control\n");
> -		pr_err_once("kvm: host upgrade recommended\n");
> +		pr_err_once("host does not support poll control\n");
> +		pr_err_once("host upgrade recommended\n");
>  		return;
>  	}
>  
> -- 
> 1.8.3.1
> 

Re: [PATCH v3 3/4] xen: Mark "xen_nopvspin" parameter obsolete and map it to "nopvspin"

[Sean Christopherson]

On Mon, Sep 30, 2019 at 08:44:38PM +0800, Zhenzhong Duan wrote:
> Fix stale description of "xen_nopvspin" as we use qspinlock now.
> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> Reviewed-by: Juergen Gross <jgross@suse.com>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: Juergen Gross <jgross@suse.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  7 ++++---
>  arch/x86/xen/spinlock.c                         | 13 +++++++------
>  2 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 4b956d8..1f0a62f 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -5303,8 +5303,9 @@
>  			never -- do not unplug even if version check succeeds
>  
>  	xen_nopvspin	[X86,XEN]
> -			Disables the ticketlock slowpath using Xen PV
> -			optimizations.
> +			Disables the qspinlock slowpath using Xen PV optimizations.
> +			This parameter is obsoleted by "nopvspin" parameter, which
> +			has equivalent effect for XEN platform.
>  
>  	xen_nopv	[X86]
>  			Disables the PV optimizations forcing the HVM guest to
> @@ -5330,7 +5331,7 @@
>  			as generic guest with no PV drivers. Currently support
>  			XEN HVM, KVM, HYPER_V and VMWARE guest.
>  
> -	nopvspin	[X86,KVM] Disables the qspinlock slow path
> +	nopvspin	[X86,XEN,KVM] Disables the qspinlock slow path
>  			using PV optimizations which allow the hypervisor to
>  			'idle' the guest on lock contention.
>  
> diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
> index 6deb490..092a53f 100644
> --- a/arch/x86/xen/spinlock.c
> +++ b/arch/x86/xen/spinlock.c
> @@ -18,7 +18,6 @@
>  static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
>  static DEFINE_PER_CPU(char *, irq_name);
>  static DEFINE_PER_CPU(atomic_t, xen_qlock_wait_nest);
> -static bool xen_pvspin = true;
>  
>  static void xen_qlock_kick(int cpu)
>  {
> @@ -68,7 +67,7 @@ void xen_init_lock_cpu(int cpu)
>  	int irq;
>  	char *name;
>  
> -	if (!xen_pvspin)
> +	if (!pvspin)
>  		return;
>  
>  	WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
> @@ -93,7 +92,7 @@ void xen_init_lock_cpu(int cpu)
>  
>  void xen_uninit_lock_cpu(int cpu)
>  {
> -	if (!xen_pvspin)
> +	if (!pvspin)
>  		return;
>  
>  	unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
> @@ -117,9 +116,9 @@ void __init xen_init_spinlocks(void)
>  
>  	/*  Don't need to use pvqspinlock code if there is only 1 vCPU. */
>  	if (num_possible_cpus() == 1)
> -		xen_pvspin = false;
> +		pvspin = false;

As suggested in the other patch, if you incorporate pvspin (or nopvspin)
into xen_pvspin then the param can be __initdata and the diff for this
patch will be smaller, e.g. you wouldn't need the xen_domain() shenanigans
in xen_parse_nopvspin().

> -	if (!xen_pvspin) {
> +	if (!pvspin) {
>  		printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
>  		static_branch_disable(&virt_spin_lock_key);
>  		return;
> @@ -137,7 +136,9 @@ void __init xen_init_spinlocks(void)
>  
>  static __init int xen_parse_nopvspin(char *arg)
>  {
> -	xen_pvspin = false;
> +	pr_notice("\"xen_nopvspin\" is deprecated, please use \"nopvspin\" instead\n");
> +	if (xen_domain())
> +		pvspin = false;
>  	return 0;
>  }
>  early_param("xen_nopvspin", xen_parse_nopvspin);
> -- 
> 1.8.3.1
> 

Re: [PATCH v3 4/4] x86/hyperv: Mark "hv_nopvspin" parameter obsolete and map it to "nopvspin"

[Sean Christopherson]

On Mon, Sep 30, 2019 at 08:44:39PM +0800, Zhenzhong Duan wrote:
> Includes asm/hypervisor.h in order to reference x86_hyper_type.
> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: "K. Y. Srinivasan" <kys@microsoft.com>
> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: Stephen Hemminger <sthemmin@microsoft.com>
> Cc: Sasha Levin <sashal@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 6 +++++-
>  arch/x86/hyperv/hv_spinlock.c                   | 9 +++++----
>  2 files changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 1f0a62f..43f922c 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1436,6 +1436,10 @@
>  	hv_nopvspin	[X86,HYPER_V] Disables the paravirt spinlock optimizations
>  				      which allow the hypervisor to 'idle' the
>  				      guest on lock contention.
> +				      This parameter is obsoleted by "nopvspin"
> +				      parameter, which has equivalent effect for
> +				      HYPER_V platform.
> +
>  
>  	keep_bootcon	[KNL]
>  			Do not unregister boot console at start. This is only
> @@ -5331,7 +5335,7 @@
>  			as generic guest with no PV drivers. Currently support
>  			XEN HVM, KVM, HYPER_V and VMWARE guest.
>  
> -	nopvspin	[X86,XEN,KVM] Disables the qspinlock slow path
> +	nopvspin	[X86,XEN,KVM,HYPER_V] Disables the qspinlock slow path
>  			using PV optimizations which allow the hypervisor to
>  			'idle' the guest on lock contention.
>  
> diff --git a/arch/x86/hyperv/hv_spinlock.c b/arch/x86/hyperv/hv_spinlock.c
> index 07f21a0..e00e319 100644
> --- a/arch/x86/hyperv/hv_spinlock.c
> +++ b/arch/x86/hyperv/hv_spinlock.c
> @@ -12,12 +12,11 @@
>  
>  #include <linux/spinlock.h>
>  
> +#include <asm/hypervisor.h>
>  #include <asm/mshyperv.h>
>  #include <asm/paravirt.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);
> @@ -64,7 +63,7 @@ __visible bool hv_vcpu_is_preempted(int vcpu)
>  
>  void __init hv_init_spinlocks(void)
>  {
> -	if (!hv_pvspin || !apic ||
> +	if (!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");
> @@ -82,7 +81,9 @@ void __init hv_init_spinlocks(void)
>  
>  static __init int hv_parse_nopvspin(char *arg)
>  {
> -	hv_pvspin = false;
> +	pr_notice("\"hv_nopvspin\" is deprecated, please use \"nopvspin\" instead\n");
> +	if (x86_hyper_type == X86_HYPER_MS_HYPERV)
> +		pvspin = false;

Personal preference would be to keep the hv_pvspin variable and add the
extra check in hv_init_spinlocks().

>  	return 0;
>  }
>  early_param("hv_nopvspin", hv_parse_nopvspin);
> -- 
> 1.8.3.1
> 

Re: [PATCH v3 1/4] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks

[Zhenzhong Duan]

On 2019/10/3 1:10, Sean Christopherson wrote:

> On Mon, Sep 30, 2019 at 08:44:36PM +0800, Zhenzhong Duan wrote:
>> There are cases where a guest tries to switch spinlocks to bare metal
>> behavior (e.g. by setting "xen_nopvspin" on XEN platform and
>> "hv_nopvspin" on HYPER_V).
>>
>> That feature is missed on KVM, add a new parameter "nopvspin" to disable
>> PV spinlocks for KVM guest.
>>
>> This new parameter is also used to replace "xen_nopvspin" and
>> "hv_nopvspin".
> This is confusing as there are no Xen or Hyper-V changes in this patch.
> Please make it clear that you're talking about future patches, e.g.:
>
>    The new 'nopvspin' parameter will also replace Xen and Hyper-V specific
>    parameters in future patches.

Will fix

>
>> The global variable pvspin isn't defined as __initdata as it's used at
>> runtime by XEN guest.
> Same comment as above regarding what this patch is doing versus what will
> be done in the future.  Arguably you should even mark it __initdata in
> this patch and deal with conflict in the Xen patch, e.g. use it only to
> set the existing xen_pvspin variable.

Will fix

>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>

......snip

>>   /**
>> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
>> index e820568..a4f108d 100644
>> --- a/arch/x86/kernel/kvm.c
>> +++ b/arch/x86/kernel/kvm.c
>> @@ -842,6 +842,13 @@ void __init kvm_spinlock_init(void)
>>   	if (num_possible_cpus() == 1)
>>   		return;
>>   
>> +	if (!pvspin) {
>> +		pr_info("PV spinlocks disabled\n");
>> +		static_branch_disable(&virt_spin_lock_key);
>> +		return;
>> +	}
>> +	pr_info("PV spinlocks enabled\n");
> These prints could be confusing as KVM also disables PV spinlocks when it
> sees KVM_HINTS_REALTIME.

What about below:

pr_info("PV spinlocks disabled forced by \"nopvspin\" parameter.\n");

Or you prefer separate print for each disabling like below?

         /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
         if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)) {
                 pr_info("PV spinlocks disabled, KVM_FEATURE_PV_UNHALT feature needed.\n");
                 return;
         }

         if (kvm_para_has_hint(KVM_HINTS_REALTIME)) {
                 pr_info("PV spinlocks disabled, having non-preemption hints.\n");
                 return;
         }

         /* Don't use the pvqspinlock code if there is only 1 vCPU. */
         if (num_possible_cpus() == 1) {
                 pr_info("PV spinlocks disabled on UP.\n");
                 return;
         }
	if (!pvspin) {
		pr_info("PV spinlocks disabled forced by \"nopvspin\" parameter.\n");
		static_branch_disable(&virt_spin_lock_key);
		return;
	}
	pr_info("PV spinlocks enabled\n");

>
>> +
>>   	__pv_init_lock_hash();
>>   	pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
>>   	pv_ops.lock.queued_spin_unlock =
>> diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
>> index 2473f10..945b510 100644
>> --- a/kernel/locking/qspinlock.c
>> +++ b/kernel/locking/qspinlock.c
>> @@ -580,4 +580,11 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
>>   #include "qspinlock_paravirt.h"
>>   #include "qspinlock.c"
>>   
>> +bool pvspin = true;
> This can be __ro_after_init, or probably better __initdata and have Xen
> snapshot the value for its use case.

I will use __initdata

>
> Personal preference: I'd invert the bool and name it nopvspin to make it
> easier to connect the variable to the kernel param.

OK, will do that.  Thanks for review for all the patches.

Zhenzhong

Re: [PATCH v3 2/4] x86/kvm: Change print code to use pr_*() format

[Zhenzhong Duan]

On 2019/10/3 1:15, Sean Christopherson wrote:

> On Mon, Sep 30, 2019 at 08:44:37PM +0800, Zhenzhong Duan wrote:
>> pr_*() is preferred than printk(KERN_* ...), after change all the print
>> in arch/x86/kernel/kvm.c will have "KVM: xxx" style.
>>
>> No functional change.
>>
>> Suggested-by: Vitaly Kuznetsov<vkuznets@redhat.com>
> This wasn't really suggested by Vitaly, he just requested it be done in a
> separate patch.

Will fix.

>
>> Signed-off-by: Zhenzhong Duan<zhenzhong.duan@oracle.com>
>> Cc: Paolo Bonzini<pbonzini@redhat.com>
>> Cc: Radim Krcmar<rkrcmar@redhat.com>
>> Cc: Sean Christopherson<sean.j.christopherson@intel.com>
>> Cc: Vitaly Kuznetsov<vkuznets@redhat.com>
>> Cc: Wanpeng Li<wanpengli@tencent.com>
>> Cc: Jim Mattson<jmattson@google.com>
>> Cc: Joerg Roedel<joro@8bytes.org>
>> Cc: Thomas Gleixner<tglx@linutronix.de>
>> Cc: Ingo Molnar<mingo@redhat.com>
>> Cc: Borislav Petkov<bp@alien8.de>
>> Cc: "H. Peter Anvin"<hpa@zytor.com>
>> ---
>>   arch/x86/kernel/kvm.c | 24 ++++++++++++------------
>>   1 file changed, 12 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
>> index a4f108d..ce4f578 100644
>> --- a/arch/x86/kernel/kvm.c
>> +++ b/arch/x86/kernel/kvm.c
>> @@ -7,6 +7,8 @@
>>    *   Authors: Anthony Liguori<aliguori@us.ibm.com>
>>    */
>>   
>> +#define pr_fmt(fmt) "KVM: " fmt
> Not a fan of "KVM" as the prefix as it's easily confused with KVM the
> hypervisor.  Maybe "kvm_guest"?

Yeah, looks better, will change to"kvm_guest". Thanks

Zhenzhong

Re: [PATCH v3 3/4] xen: Mark "xen_nopvspin" parameter obsolete and map it to "nopvspin"

[Zhenzhong Duan]

On 2019/10/3 1:18, Sean Christopherson wrote:
> On Mon, Sep 30, 2019 at 08:44:38PM +0800, Zhenzhong Duan wrote:
>> Fix stale description of "xen_nopvspin" as we use qspinlock now.
>>
>> Signed-off-by: Zhenzhong Duan<zhenzhong.duan@oracle.com>
>> Reviewed-by: Juergen Gross<jgross@suse.com>
>> Cc: Jonathan Corbet<corbet@lwn.net>
>> Cc: Boris Ostrovsky<boris.ostrovsky@oracle.com>
>> Cc: Juergen Gross<jgross@suse.com>
>> Cc: Stefano Stabellini<sstabellini@kernel.org>
>> Cc: Thomas Gleixner<tglx@linutronix.de>
>> Cc: Ingo Molnar<mingo@redhat.com>
>> Cc: Borislav Petkov<bp@alien8.de>
>> Cc: "H. Peter Anvin"<hpa@zytor.com>
>> ---
...snip
>> @@ -93,7 +92,7 @@ void xen_init_lock_cpu(int cpu)
>>   
>>   void xen_uninit_lock_cpu(int cpu)
>>   {
>> -	if (!xen_pvspin)
>> +	if (!pvspin)
>>   		return;
>>   
>>   	unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
>> @@ -117,9 +116,9 @@ void __init xen_init_spinlocks(void)
>>   
>>   	/*  Don't need to use pvqspinlock code if there is only 1 vCPU. */
>>   	if (num_possible_cpus() == 1)
>> -		xen_pvspin = false;
>> +		pvspin = false;
> As suggested in the other patch, if you incorporate pvspin (or nopvspin)
> into xen_pvspin then the param can be __initdata and the diff for this
> patch will be smaller, e.g. you wouldn't need the xen_domain() shenanigans
> in xen_parse_nopvspin().

Ok, will fix. Thanks

Zhenzhong

Re: [PATCH v3 4/4] x86/hyperv: Mark "hv_nopvspin" parameter obsolete and map it to "nopvspin"

[Zhenzhong Duan]

On 2019/10/3 1:19, Sean Christopherson wrote:
> On Mon, Sep 30, 2019 at 08:44:39PM +0800, Zhenzhong Duan wrote:
>> Includes asm/hypervisor.h in order to reference x86_hyper_type.
>>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
>> Cc: Jonathan Corbet <corbet@lwn.net>
>> Cc: "K. Y. Srinivasan" <kys@microsoft.com>
>> Cc: Haiyang Zhang <haiyangz@microsoft.com>
>> Cc: Stephen Hemminger <sthemmin@microsoft.com>
>> Cc: Sasha Levin <sashal@kernel.org>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Borislav Petkov <bp@alien8.de>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> ---
...snip
>> @@ -64,7 +63,7 @@ __visible bool hv_vcpu_is_preempted(int vcpu)
>>   
>>   void __init hv_init_spinlocks(void)
>>   {
>> -	if (!hv_pvspin || !apic ||
>> +	if (!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");
>> @@ -82,7 +81,9 @@ void __init hv_init_spinlocks(void)
>>   
>>   static __init int hv_parse_nopvspin(char *arg)
>>   {
>> -	hv_pvspin = false;
>> +	pr_notice("\"hv_nopvspin\" is deprecated, please use \"nopvspin\" instead\n");
>> +	if (x86_hyper_type == X86_HYPER_MS_HYPERV)
>> +		pvspin = false;
> Personal preference would be to keep the hv_pvspin variable and add the
> extra check in hv_init_spinlocks().

OK, will do that way. Thanks

Zhenzhong