From: Zhenzhong Duan <zhenzhong.duan@oracle.com>
To: linux-kernel@vger.kernel.org
Cc: vkuznets@redhat.com, linux-hyperv@vger.kernel.org,
kvm@vger.kernel.org, Zhenzhong Duan <zhenzhong.duan@oracle.com>,
Jonathan Corbet <corbet@lwn.net>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Radim Krcmar <rkrcmar@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will@kernel.org>
Subject: [PATCH v2 1/4] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks
Date: Mon, 30 Sep 2019 20:08:57 +0800 [thread overview]
Message-ID: <1569845340-11884-2-git-send-email-zhenzhong.duan@oracle.com> (raw)
In-Reply-To: <1569845340-11884-1-git-send-email-zhenzhong.duan@oracle.com>
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
next prev parent reply other threads:[~2019-10-01 12:06 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-30 12:08 [PATCH v2 0/3] Add a unified parameter "nopvspin" Zhenzhong Duan
2019-09-30 12:08 ` Zhenzhong Duan [this message]
2019-09-30 12:08 ` [PATCH v2 2/4] x86/kvm: Change print code to use pr_*() format Zhenzhong Duan
2019-09-30 12:08 ` [PATCH v2 3/4] xen: Mark "xen_nopvspin" parameter obsolete and map it to "nopvspin" Zhenzhong Duan
2019-09-30 12:09 ` [PATCH v2 4/4] x86/hyperv: Mark "hv_nopvspin" " Zhenzhong Duan
2019-10-01 12:19 ` [PATCH v2 0/3] Add a unified parameter "nopvspin" Zhenzhong Duan
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