* [PATCH v5 0/5] Add a unified parameter "nopvspin"
@ 2019-10-07 9:04 Zhenzhong Duan
2019-10-07 9:04 ` [PATCH v5 1/5] Revert "KVM: X86: Fix setup the virt_spin_lock_key before static key get initialized" Zhenzhong Duan
` (5 more replies)
0 siblings, 6 replies; 13+ messages in thread
From: Zhenzhong Duan @ 2019-10-07 9:04 UTC (permalink / raw)
To: linux-kernel
Cc: vkuznets, linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal,
tglx, mingo, bp, pbonzini, rkrcmar, sean.j.christopherson,
wanpengli, jmattson, joro, boris.ostrovsky, jgross, sstabellini,
peterz, 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.
v5:
PATCH1: new patch to revert a currently unnecessory commit,
code is simpler a bit after that change. [Boris Ostrovsky]
PATCH3: fold 'if' statement,add comments on virt_spin_lock_key,
reorder with PATCH2 to better reflect dependency
PATCH4: fold 'if' statement, add Reviewed-by [Boris Ostrovsky]
PATCH5: add Reviewed-by [Michael Kelley]
v4:
PATCH1: use variable name nopvspin instead of pvspin and
defined it as __initdata, changed print message,
updated patch description [Sean Christopherson]
PATCH2: remove Suggested-by, use "kvm-guest:" prefix [Sean Christopherson]
PATCH3: make variable nopvsin and xen_pvspin coexist
remove Reviewed-by due to code change [Sean Christopherson]
PATCH4: make variable nopvsin and hv_pvspin coexist [Sean Christopherson]
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]
Zhenzhong Duan (5):
Revert "KVM: X86: Fix setup the virt_spin_lock_key before static key
get initialized"
x86/kvm: Change print code to use pr_*() format
x86/kvm: Add "nopvspin" parameter to disable PV spinlocks
xen: Mark "xen_nopvspin" parameter obsolete
x86/hyperv: Mark "hv_nopvspin" parameter obsolete
Documentation/admin-guide/kernel-parameters.txt | 14 +++++-
arch/x86/hyperv/hv_spinlock.c | 4 ++
arch/x86/include/asm/qspinlock.h | 1 +
arch/x86/kernel/kvm.c | 63 ++++++++++++++-----------
arch/x86/xen/spinlock.c | 4 +-
kernel/locking/qspinlock.c | 7 +++
6 files changed, 62 insertions(+), 31 deletions(-)
--
1.8.3.1
^ permalink raw reply [flat|nested] 13+ messages in thread
* [PATCH v5 1/5] Revert "KVM: X86: Fix setup the virt_spin_lock_key before static key get initialized"
2019-10-07 9:04 [PATCH v5 0/5] Add a unified parameter "nopvspin" Zhenzhong Duan
@ 2019-10-07 9:04 ` Zhenzhong Duan
2019-10-13 9:08 ` Vitaly Kuznetsov
2019-10-07 9:04 ` [PATCH v5 2/5] x86/kvm: Change print code to use pr_*() format Zhenzhong Duan
` (4 subsequent siblings)
5 siblings, 1 reply; 13+ messages in thread
From: Zhenzhong Duan @ 2019-10-07 9:04 UTC (permalink / raw)
To: linux-kernel
Cc: vkuznets, linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal,
tglx, mingo, bp, pbonzini, rkrcmar, sean.j.christopherson,
wanpengli, jmattson, joro, boris.ostrovsky, jgross, sstabellini,
peterz, Zhenzhong Duan, H. Peter Anvin
This reverts commit 34226b6b70980a8f81fff3c09a2c889f77edeeff.
Commit 8990cac6e5ea ("x86/jump_label: Initialize static branching
early") adds jump_label_init() call in setup_arch() to make static
keys initialized early, so we could use the original simpler code
again.
The similar change for XEN is in commit 090d54bcbc54 ("Revert
"x86/paravirt: Set up the virt_spin_lock_key after static keys get
initialized"")
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 | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index e820568..3bc6a266 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -527,13 +527,6 @@ static void kvm_smp_send_call_func_ipi(const struct cpumask *mask)
}
}
-static void __init kvm_smp_prepare_cpus(unsigned int max_cpus)
-{
- native_smp_prepare_cpus(max_cpus);
- if (kvm_para_has_hint(KVM_HINTS_REALTIME))
- static_branch_disable(&virt_spin_lock_key);
-}
-
static void __init kvm_smp_prepare_boot_cpu(void)
{
/*
@@ -633,7 +626,6 @@ static void __init kvm_guest_init(void)
apic_set_eoi_write(kvm_guest_apic_eoi_write);
#ifdef CONFIG_SMP
- smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus;
smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
if (kvm_para_has_feature(KVM_FEATURE_PV_SCHED_YIELD) &&
!kvm_para_has_hint(KVM_HINTS_REALTIME) &&
@@ -835,8 +827,10 @@ void __init kvm_spinlock_init(void)
if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
return;
- if (kvm_para_has_hint(KVM_HINTS_REALTIME))
+ if (kvm_para_has_hint(KVM_HINTS_REALTIME)) {
+ static_branch_disable(&virt_spin_lock_key);
return;
+ }
/* Don't use the pvqspinlock code if there is only 1 vCPU. */
if (num_possible_cpus() == 1)
--
1.8.3.1
^ permalink raw reply related [flat|nested] 13+ messages in thread
* [PATCH v5 2/5] x86/kvm: Change print code to use pr_*() format
2019-10-07 9:04 [PATCH v5 0/5] Add a unified parameter "nopvspin" Zhenzhong Duan
2019-10-07 9:04 ` [PATCH v5 1/5] Revert "KVM: X86: Fix setup the virt_spin_lock_key before static key get initialized" Zhenzhong Duan
@ 2019-10-07 9:04 ` Zhenzhong Duan
2019-10-13 9:06 ` Vitaly Kuznetsov
2019-10-07 9:04 ` [PATCH v5 3/5] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks Zhenzhong Duan
` (3 subsequent siblings)
5 siblings, 1 reply; 13+ messages in thread
From: Zhenzhong Duan @ 2019-10-07 9:04 UTC (permalink / raw)
To: linux-kernel
Cc: vkuznets, linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal,
tglx, mingo, bp, pbonzini, rkrcmar, sean.j.christopherson,
wanpengli, jmattson, joro, boris.ostrovsky, jgross, sstabellini,
peterz, Zhenzhong Duan, H. Peter Anvin
pr_*() is preferred than printk(KERN_* ...), after change all the print
in arch/x86/kernel/kvm.c will have "kvm_guest: xxx" style.
No functional change.
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 | 30 ++++++++++++++++--------------
1 file changed, 16 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 3bc6a266..ef836d6 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_guest: " 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)
@@ -469,7 +469,8 @@ static void __send_ipi_mask(const struct cpumask *mask, int vector)
} else {
ret = kvm_hypercall4(KVM_HC_SEND_IPI, (unsigned long)ipi_bitmap,
(unsigned long)(ipi_bitmap >> BITS_PER_LONG), min, icr);
- WARN_ONCE(ret < 0, "KVM: failed to send PV IPI: %ld", ret);
+ WARN_ONCE(ret < 0, "kvm_guest: failed to send PV IPI: %ld",
+ ret);
min = max = apic_id;
ipi_bitmap = 0;
}
@@ -479,7 +480,8 @@ static void __send_ipi_mask(const struct cpumask *mask, int vector)
if (ipi_bitmap) {
ret = kvm_hypercall4(KVM_HC_SEND_IPI, (unsigned long)ipi_bitmap,
(unsigned long)(ipi_bitmap >> BITS_PER_LONG), min, icr);
- WARN_ONCE(ret < 0, "KVM: failed to send PV IPI: %ld", ret);
+ WARN_ONCE(ret < 0, "kvm_guest: failed to send PV IPI: %ld",
+ ret);
}
local_irq_restore(flags);
@@ -509,7 +511,7 @@ 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)
@@ -631,11 +633,11 @@ 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();
@@ -738,7 +740,7 @@ 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;
@@ -866,8 +868,8 @@ 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
^ permalink raw reply related [flat|nested] 13+ messages in thread
* [PATCH v5 3/5] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks
2019-10-07 9:04 [PATCH v5 0/5] Add a unified parameter "nopvspin" Zhenzhong Duan
2019-10-07 9:04 ` [PATCH v5 1/5] Revert "KVM: X86: Fix setup the virt_spin_lock_key before static key get initialized" Zhenzhong Duan
2019-10-07 9:04 ` [PATCH v5 2/5] x86/kvm: Change print code to use pr_*() format Zhenzhong Duan
@ 2019-10-07 9:04 ` Zhenzhong Duan
2019-10-13 9:02 ` Vitaly Kuznetsov
2019-10-07 9:04 ` [PATCH v5 4/5] xen: Mark "xen_nopvspin" parameter obsolete Zhenzhong Duan
` (2 subsequent siblings)
5 siblings, 1 reply; 13+ messages in thread
From: Zhenzhong Duan @ 2019-10-07 9:04 UTC (permalink / raw)
To: linux-kernel
Cc: vkuznets, linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal,
tglx, mingo, bp, pbonzini, rkrcmar, sean.j.christopherson,
wanpengli, jmattson, joro, boris.ostrovsky, jgross, sstabellini,
peterz, Zhenzhong Duan, Jonathan Corbet, H. Peter Anvin,
Will Deacon
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.
The new 'nopvspin' parameter will also replace Xen and Hyper-V specific
parameters in future patches.
Define variable nopvsin as global because it will be used in future
patches as above.
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 | 5 +++++
arch/x86/include/asm/qspinlock.h | 1 +
arch/x86/kernel/kvm.c | 21 +++++++++++++++++----
kernel/locking/qspinlock.c | 7 +++++++
4 files changed, 30 insertions(+), 4 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c7ac2f3..89d77ea 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5330,6 +5330,11 @@
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..d86ab94 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 nopvspin;
#define queued_spin_unlock queued_spin_unlock
/**
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index ef836d6..6e14bd4 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -825,18 +825,31 @@ __visible bool __kvm_vcpu_is_preempted(long cpu)
*/
void __init kvm_spinlock_init(void)
{
- /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
- if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
+ /*
+ * Disable PV qspinlocks if host kernel doesn't support
+ * KVM_FEATURE_PV_UNHALT feature or there is only 1 vCPU.
+ * virt_spin_lock_key is enabled to avoid lock holder
+ * preemption issue.
+ */
+ if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT) ||
+ num_possible_cpus() == 1) {
+ pr_info("PV spinlocks disabled\n");
return;
+ }
if (kvm_para_has_hint(KVM_HINTS_REALTIME)) {
+ pr_info("PV spinlocks disabled with KVM_HINTS_REALTIME hints.\n");
static_branch_disable(&virt_spin_lock_key);
return;
}
- /* Don't use the pvqspinlock code if there is only 1 vCPU. */
- if (num_possible_cpus() == 1)
+ if (nopvspin) {
+ 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;
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 2473f10..75193d6 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 nopvspin __initdata;
+static __init int parse_nopvspin(char *arg)
+{
+ nopvspin = true;
+ return 0;
+}
+early_param("nopvspin", parse_nopvspin);
#endif
--
1.8.3.1
^ permalink raw reply related [flat|nested] 13+ messages in thread
* [PATCH v5 4/5] xen: Mark "xen_nopvspin" parameter obsolete
2019-10-07 9:04 [PATCH v5 0/5] Add a unified parameter "nopvspin" Zhenzhong Duan
` (2 preceding siblings ...)
2019-10-07 9:04 ` [PATCH v5 3/5] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks Zhenzhong Duan
@ 2019-10-07 9:04 ` Zhenzhong Duan
2019-10-07 9:04 ` [PATCH v5 5/5] x86/hyperv: Mark "hv_nopvspin" " Zhenzhong Duan
2019-10-12 8:40 ` [PATCH v5 0/5] Add a unified parameter "nopvspin" Zhenzhong Duan
5 siblings, 0 replies; 13+ messages in thread
From: Zhenzhong Duan @ 2019-10-07 9:04 UTC (permalink / raw)
To: linux-kernel
Cc: vkuznets, linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal,
tglx, mingo, bp, pbonzini, rkrcmar, sean.j.christopherson,
wanpengli, jmattson, joro, boris.ostrovsky, jgross, sstabellini,
peterz, Zhenzhong Duan, Jonathan Corbet, H. Peter Anvin
Map "xen_nopvspin" to "nopvspin", fix stale description of "xen_nopvspin"
as we use qspinlock now.
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.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 | 4 ++--
2 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 89d77ea..df1eacc 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]
+ 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..799f4eb 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -114,9 +114,8 @@ void xen_uninit_lock_cpu(int cpu)
*/
void __init xen_init_spinlocks(void)
{
-
/* Don't need to use pvqspinlock code if there is only 1 vCPU. */
- if (num_possible_cpus() == 1)
+ if (num_possible_cpus() == 1 || nopvspin)
xen_pvspin = false;
if (!xen_pvspin) {
@@ -137,6 +136,7 @@ void __init xen_init_spinlocks(void)
static __init int xen_parse_nopvspin(char *arg)
{
+ pr_notice("\"xen_nopvspin\" is deprecated, please use \"nopvspin\" instead\n");
xen_pvspin = false;
return 0;
}
--
1.8.3.1
^ permalink raw reply related [flat|nested] 13+ messages in thread
* [PATCH v5 5/5] x86/hyperv: Mark "hv_nopvspin" parameter obsolete
2019-10-07 9:04 [PATCH v5 0/5] Add a unified parameter "nopvspin" Zhenzhong Duan
` (3 preceding siblings ...)
2019-10-07 9:04 ` [PATCH v5 4/5] xen: Mark "xen_nopvspin" parameter obsolete Zhenzhong Duan
@ 2019-10-07 9:04 ` Zhenzhong Duan
2019-10-12 8:40 ` [PATCH v5 0/5] Add a unified parameter "nopvspin" Zhenzhong Duan
5 siblings, 0 replies; 13+ messages in thread
From: Zhenzhong Duan @ 2019-10-07 9:04 UTC (permalink / raw)
To: linux-kernel
Cc: vkuznets, linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal,
tglx, mingo, bp, pbonzini, rkrcmar, sean.j.christopherson,
wanpengli, jmattson, joro, boris.ostrovsky, jgross, sstabellini,
peterz, Zhenzhong Duan, Jonathan Corbet, H. Peter Anvin
Map "hv_nopvspin" to "nopvspin".
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.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 | 4 ++++
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index df1eacc..08c6d34 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]
+ 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..47c7d6c 100644
--- a/arch/x86/hyperv/hv_spinlock.c
+++ b/arch/x86/hyperv/hv_spinlock.c
@@ -64,6 +64,9 @@ __visible bool hv_vcpu_is_preempted(int vcpu)
void __init hv_init_spinlocks(void)
{
+ if (nopvspin)
+ hv_pvspin = false;
+
if (!hv_pvspin || !apic ||
!(ms_hyperv.hints & HV_X64_CLUSTER_IPI_RECOMMENDED) ||
!(ms_hyperv.features & HV_X64_MSR_GUEST_IDLE_AVAILABLE)) {
@@ -82,6 +85,7 @@ void __init hv_init_spinlocks(void)
static __init int hv_parse_nopvspin(char *arg)
{
+ pr_notice("\"hv_nopvspin\" is deprecated, please use \"nopvspin\" instead\n");
hv_pvspin = false;
return 0;
}
--
1.8.3.1
^ permalink raw reply related [flat|nested] 13+ messages in thread
* Re: [PATCH v5 0/5] Add a unified parameter "nopvspin"
2019-10-07 9:04 [PATCH v5 0/5] Add a unified parameter "nopvspin" Zhenzhong Duan
` (4 preceding siblings ...)
2019-10-07 9:04 ` [PATCH v5 5/5] x86/hyperv: Mark "hv_nopvspin" " Zhenzhong Duan
@ 2019-10-12 8:40 ` Zhenzhong Duan
5 siblings, 0 replies; 13+ messages in thread
From: Zhenzhong Duan @ 2019-10-12 8:40 UTC (permalink / raw)
To: linux-kernel
Cc: vkuznets, linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal,
tglx, mingo, bp, pbonzini, rkrcmar, sean.j.christopherson,
wanpengli, jmattson, joro, boris.ostrovsky, jgross, sstabellini,
peterz
The last two patches are reviewed, will any KVM expert be willing to
review the first three patches?
They are all KVM related changes. Thanks
Zhenzhong
On 2019/10/7 17:04, Zhenzhong Duan wrote:
> 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.
>
> v5:
> PATCH1: new patch to revert a currently unnecessory commit,
> code is simpler a bit after that change. [Boris Ostrovsky]
> PATCH3: fold 'if' statement,add comments on virt_spin_lock_key,
> reorder with PATCH2 to better reflect dependency
> PATCH4: fold 'if' statement, add Reviewed-by [Boris Ostrovsky]
> PATCH5: add Reviewed-by [Michael Kelley]
>
> v4:
> PATCH1: use variable name nopvspin instead of pvspin and
> defined it as __initdata, changed print message,
> updated patch description [Sean Christopherson]
> PATCH2: remove Suggested-by, use "kvm-guest:" prefix [Sean Christopherson]
> PATCH3: make variable nopvsin and xen_pvspin coexist
> remove Reviewed-by due to code change [Sean Christopherson]
> PATCH4: make variable nopvsin and hv_pvspin coexist [Sean Christopherson]
>
> 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]
>
> Zhenzhong Duan (5):
> Revert "KVM: X86: Fix setup the virt_spin_lock_key before static key
> get initialized"
> x86/kvm: Change print code to use pr_*() format
> x86/kvm: Add "nopvspin" parameter to disable PV spinlocks
> xen: Mark "xen_nopvspin" parameter obsolete
> x86/hyperv: Mark "hv_nopvspin" parameter obsolete
>
> Documentation/admin-guide/kernel-parameters.txt | 14 +++++-
> arch/x86/hyperv/hv_spinlock.c | 4 ++
> arch/x86/include/asm/qspinlock.h | 1 +
> arch/x86/kernel/kvm.c | 63 ++++++++++++++-----------
> arch/x86/xen/spinlock.c | 4 +-
> kernel/locking/qspinlock.c | 7 +++
> 6 files changed, 62 insertions(+), 31 deletions(-)
>
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v5 3/5] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks
2019-10-07 9:04 ` [PATCH v5 3/5] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks Zhenzhong Duan
@ 2019-10-13 9:02 ` Vitaly Kuznetsov
2019-10-14 1:52 ` Zhenzhong Duan
0 siblings, 1 reply; 13+ messages in thread
From: Vitaly Kuznetsov @ 2019-10-13 9:02 UTC (permalink / raw)
To: Zhenzhong Duan, linux-kernel
Cc: linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal, tglx, mingo,
bp, pbonzini, rkrcmar, sean.j.christopherson, wanpengli,
jmattson, joro, boris.ostrovsky, jgross, sstabellini, peterz,
Zhenzhong Duan, Jonathan Corbet, H. Peter Anvin, Will Deacon
Zhenzhong Duan <zhenzhong.duan@oracle.com> writes:
> 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.
>
> The new 'nopvspin' parameter will also replace Xen and Hyper-V specific
> parameters in future patches.
>
> Define variable nopvsin as global because it will be used in future
> patches as above.
>
> 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 | 5 +++++
> arch/x86/include/asm/qspinlock.h | 1 +
> arch/x86/kernel/kvm.c | 21 +++++++++++++++++----
> kernel/locking/qspinlock.c | 7 +++++++
> 4 files changed, 30 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index c7ac2f3..89d77ea 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -5330,6 +5330,11 @@
> 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..d86ab94 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 nopvspin;
>
> #define queued_spin_unlock queued_spin_unlock
> /**
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index ef836d6..6e14bd4 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -825,18 +825,31 @@ __visible bool __kvm_vcpu_is_preempted(long cpu)
> */
> void __init kvm_spinlock_init(void)
> {
> - /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
> - if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
> + /*
> + * Disable PV qspinlocks if host kernel doesn't support
> + * KVM_FEATURE_PV_UNHALT feature or there is only 1 vCPU.
> + * virt_spin_lock_key is enabled to avoid lock holder
> + * preemption issue.
> + */
> + if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT) ||
> + num_possible_cpus() == 1) {
> + pr_info("PV spinlocks disabled\n");
Why don't we need static_branch_disable(&virt_spin_lock_key) here?
Also, as you're printing the exact reason for PV spinlocks disablement
in other cases, I'd suggest separating "no host support" and "single
CPU" cases.
> return;
> + }
>
> if (kvm_para_has_hint(KVM_HINTS_REALTIME)) {
> + pr_info("PV spinlocks disabled with KVM_HINTS_REALTIME hints.\n");
> static_branch_disable(&virt_spin_lock_key);
> return;
> }
>
> - /* Don't use the pvqspinlock code if there is only 1 vCPU. */
> - if (num_possible_cpus() == 1)
> + if (nopvspin) {
> + pr_info("PV spinlocks disabled forced by \"nopvspin\" parameter.\n");
Nit: to make it sound better a comma is missing between 'disabled' and
'forced', or
"PV spinlocks forcefully disabled by ..." if you prefer.
> + 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;
> diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
> index 2473f10..75193d6 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 nopvspin __initdata;
> +static __init int parse_nopvspin(char *arg)
> +{
> + nopvspin = true;
> + return 0;
> +}
> +early_param("nopvspin", parse_nopvspin);
> #endif
--
Vitaly
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v5 2/5] x86/kvm: Change print code to use pr_*() format
2019-10-07 9:04 ` [PATCH v5 2/5] x86/kvm: Change print code to use pr_*() format Zhenzhong Duan
@ 2019-10-13 9:06 ` Vitaly Kuznetsov
2019-10-14 1:38 ` Zhenzhong Duan
0 siblings, 1 reply; 13+ messages in thread
From: Vitaly Kuznetsov @ 2019-10-13 9:06 UTC (permalink / raw)
To: Zhenzhong Duan, linux-kernel
Cc: linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal, tglx, mingo,
bp, pbonzini, rkrcmar, sean.j.christopherson, wanpengli,
jmattson, joro, boris.ostrovsky, jgross, sstabellini, peterz,
Zhenzhong Duan, H. Peter Anvin
Zhenzhong Duan <zhenzhong.duan@oracle.com> writes:
> pr_*() is preferred than printk(KERN_* ...), after change all the print
> in arch/x86/kernel/kvm.c will have "kvm_guest: xxx" style.
>
> No functional change.
>
> 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 | 30 ++++++++++++++++--------------
> 1 file changed, 16 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 3bc6a266..ef836d6 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_guest: " 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)
> @@ -469,7 +469,8 @@ static void __send_ipi_mask(const struct cpumask *mask, int vector)
> } else {
> ret = kvm_hypercall4(KVM_HC_SEND_IPI, (unsigned long)ipi_bitmap,
> (unsigned long)(ipi_bitmap >> BITS_PER_LONG), min, icr);
> - WARN_ONCE(ret < 0, "KVM: failed to send PV IPI: %ld", ret);
> + WARN_ONCE(ret < 0, "kvm_guest: failed to send PV IPI: %ld",
> + ret);
> min = max = apic_id;
> ipi_bitmap = 0;
> }
> @@ -479,7 +480,8 @@ static void __send_ipi_mask(const struct cpumask *mask, int vector)
> if (ipi_bitmap) {
> ret = kvm_hypercall4(KVM_HC_SEND_IPI, (unsigned long)ipi_bitmap,
> (unsigned long)(ipi_bitmap >> BITS_PER_LONG), min, icr);
> - WARN_ONCE(ret < 0, "KVM: failed to send PV IPI: %ld", ret);
> + WARN_ONCE(ret < 0, "kvm_guest: failed to send PV IPI: %ld",
> + ret);
> }
>
> local_irq_restore(flags);
> @@ -509,7 +511,7 @@ 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");
Not your fault but in WARN_ONCE() above we use 'PV' capitalized so I'd
suggest we converge on something: either capitalize them all or make
them all lowercase.
> }
>
> static void kvm_smp_send_call_func_ipi(const struct cpumask *mask)
> @@ -631,11 +633,11 @@ 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");
here
> }
> 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();
> @@ -738,7 +740,7 @@ 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");
and here too.
> }
>
> return 0;
> @@ -866,8 +868,8 @@ 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;
> }
Other than the above,
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
--
Vitaly
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v5 1/5] Revert "KVM: X86: Fix setup the virt_spin_lock_key before static key get initialized"
2019-10-07 9:04 ` [PATCH v5 1/5] Revert "KVM: X86: Fix setup the virt_spin_lock_key before static key get initialized" Zhenzhong Duan
@ 2019-10-13 9:08 ` Vitaly Kuznetsov
0 siblings, 0 replies; 13+ messages in thread
From: Vitaly Kuznetsov @ 2019-10-13 9:08 UTC (permalink / raw)
To: Zhenzhong Duan, linux-kernel
Cc: linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal, tglx, mingo,
bp, pbonzini, rkrcmar, sean.j.christopherson, wanpengli,
jmattson, joro, boris.ostrovsky, jgross, sstabellini, peterz,
Zhenzhong Duan, H. Peter Anvin
Zhenzhong Duan <zhenzhong.duan@oracle.com> writes:
> This reverts commit 34226b6b70980a8f81fff3c09a2c889f77edeeff.
>
> Commit 8990cac6e5ea ("x86/jump_label: Initialize static branching
> early") adds jump_label_init() call in setup_arch() to make static
> keys initialized early, so we could use the original simpler code
> again.
>
> The similar change for XEN is in commit 090d54bcbc54 ("Revert
> "x86/paravirt: Set up the virt_spin_lock_key after static keys get
> initialized"")
>
> 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 | 12 +++---------
> 1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index e820568..3bc6a266 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -527,13 +527,6 @@ static void kvm_smp_send_call_func_ipi(const struct cpumask *mask)
> }
> }
>
> -static void __init kvm_smp_prepare_cpus(unsigned int max_cpus)
> -{
> - native_smp_prepare_cpus(max_cpus);
> - if (kvm_para_has_hint(KVM_HINTS_REALTIME))
> - static_branch_disable(&virt_spin_lock_key);
> -}
> -
> static void __init kvm_smp_prepare_boot_cpu(void)
> {
> /*
> @@ -633,7 +626,6 @@ static void __init kvm_guest_init(void)
> apic_set_eoi_write(kvm_guest_apic_eoi_write);
>
> #ifdef CONFIG_SMP
> - smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus;
> smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
> if (kvm_para_has_feature(KVM_FEATURE_PV_SCHED_YIELD) &&
> !kvm_para_has_hint(KVM_HINTS_REALTIME) &&
> @@ -835,8 +827,10 @@ void __init kvm_spinlock_init(void)
> if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
> return;
>
> - if (kvm_para_has_hint(KVM_HINTS_REALTIME))
> + if (kvm_para_has_hint(KVM_HINTS_REALTIME)) {
> + static_branch_disable(&virt_spin_lock_key);
> return;
> + }
>
> /* Don't use the pvqspinlock code if there is only 1 vCPU. */
> if (num_possible_cpus() == 1)
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
--
Vitaly
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v5 2/5] x86/kvm: Change print code to use pr_*() format
2019-10-13 9:06 ` Vitaly Kuznetsov
@ 2019-10-14 1:38 ` Zhenzhong Duan
0 siblings, 0 replies; 13+ messages in thread
From: Zhenzhong Duan @ 2019-10-14 1:38 UTC (permalink / raw)
To: Vitaly Kuznetsov, linux-kernel
Cc: linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal, tglx, mingo,
bp, pbonzini, rkrcmar, sean.j.christopherson, wanpengli,
jmattson, joro, boris.ostrovsky, jgross, sstabellini, peterz,
H. Peter Anvin
On 2019/10/13 17:06, Vitaly Kuznetsov wrote:
> Zhenzhong Duan <zhenzhong.duan@oracle.com> writes:
>
>> pr_*() is preferred than printk(KERN_* ...), after change all the print
>> in arch/x86/kernel/kvm.c will have "kvm_guest: xxx" style.
>>
>> No functional change.
>>
>> 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 | 30 ++++++++++++++++--------------
>> 1 file changed, 16 insertions(+), 14 deletions(-)
>>
>> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
>> index 3bc6a266..ef836d6 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_guest: " 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)
>> @@ -469,7 +469,8 @@ static void __send_ipi_mask(const struct cpumask *mask, int vector)
>> } else {
>> ret = kvm_hypercall4(KVM_HC_SEND_IPI, (unsigned long)ipi_bitmap,
>> (unsigned long)(ipi_bitmap >> BITS_PER_LONG), min, icr);
>> - WARN_ONCE(ret < 0, "KVM: failed to send PV IPI: %ld", ret);
>> + WARN_ONCE(ret < 0, "kvm_guest: failed to send PV IPI: %ld",
>> + ret);
>> min = max = apic_id;
>> ipi_bitmap = 0;
>> }
>> @@ -479,7 +480,8 @@ static void __send_ipi_mask(const struct cpumask *mask, int vector)
>> if (ipi_bitmap) {
>> ret = kvm_hypercall4(KVM_HC_SEND_IPI, (unsigned long)ipi_bitmap,
>> (unsigned long)(ipi_bitmap >> BITS_PER_LONG), min, icr);
>> - WARN_ONCE(ret < 0, "KVM: failed to send PV IPI: %ld", ret);
>> + WARN_ONCE(ret < 0, "kvm_guest: failed to send PV IPI: %ld",
>> + ret);
>> }
>>
>> local_irq_restore(flags);
>> @@ -509,7 +511,7 @@ 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");
> Not your fault but in WARN_ONCE() above we use 'PV' capitalized so I'd
> suggest we converge on something: either capitalize them all or make
> them all lowercase.
Thanks for catching, will do with 'PV' for all print.
Zhenzhong
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v5 3/5] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks
2019-10-13 9:02 ` Vitaly Kuznetsov
@ 2019-10-14 1:52 ` Zhenzhong Duan
2019-10-14 9:18 ` Vitaly Kuznetsov
0 siblings, 1 reply; 13+ messages in thread
From: Zhenzhong Duan @ 2019-10-14 1:52 UTC (permalink / raw)
To: Vitaly Kuznetsov, linux-kernel
Cc: linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal, tglx, mingo,
bp, pbonzini, rkrcmar, sean.j.christopherson, wanpengli,
jmattson, joro, boris.ostrovsky, jgross, sstabellini, peterz,
Jonathan Corbet, H. Peter Anvin, Will Deacon
On 2019/10/13 17:02, Vitaly Kuznetsov wrote:
> Zhenzhong Duan <zhenzhong.duan@oracle.com> writes:
...snip
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index ef836d6..6e14bd4 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -825,18 +825,31 @@ __visible bool __kvm_vcpu_is_preempted(long cpu)
> */
> void __init kvm_spinlock_init(void)
> {
> - /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
> - if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
> + /*
> + * Disable PV qspinlocks if host kernel doesn't support
> + * KVM_FEATURE_PV_UNHALT feature or there is only 1 vCPU.
> + * virt_spin_lock_key is enabled to avoid lock holder
> + * preemption issue.
> + */
> + if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT) ||
> + num_possible_cpus() == 1) {
> + pr_info("PV spinlocks disabled\n");
> Why don't we need static_branch_disable(&virt_spin_lock_key) here?
Thanks for review.
I have a brief explanation in above comment area.
Boris also raised the same question in v4 and see my detailed explanation
in https://lkml.org/lkml/2019/10/6/39
>
> Also, as you're printing the exact reason for PV spinlocks disablement
> in other cases, I'd suggest separating "no host support" and "single
> CPU" cases.
Will do after reaching a consensus on your first question.
>
>> return;
>> + }
>>
>> if (kvm_para_has_hint(KVM_HINTS_REALTIME)) {
>> + pr_info("PV spinlocks disabled with KVM_HINTS_REALTIME hints.\n");
>> static_branch_disable(&virt_spin_lock_key);
>> return;
>> }
>>
>> - /* Don't use the pvqspinlock code if there is only 1 vCPU. */
>> - if (num_possible_cpus() == 1)
>> + if (nopvspin) {
>> + pr_info("PV spinlocks disabled forced by \"nopvspin\" parameter.\n");
> Nit: to make it sound better a comma is missing between 'disabled' and
> 'forced', or
>
> "PV spinlocks forcefully disabled by ..." if you prefer.
Will do.
Zhenzhong
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v5 3/5] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks
2019-10-14 1:52 ` Zhenzhong Duan
@ 2019-10-14 9:18 ` Vitaly Kuznetsov
0 siblings, 0 replies; 13+ messages in thread
From: Vitaly Kuznetsov @ 2019-10-14 9:18 UTC (permalink / raw)
To: Zhenzhong Duan, linux-kernel
Cc: linux-hyperv, kvm, kys, haiyangz, sthemmin, sashal, tglx, mingo,
bp, pbonzini, rkrcmar, sean.j.christopherson, wanpengli,
jmattson, joro, boris.ostrovsky, jgross, sstabellini, peterz,
Jonathan Corbet, H. Peter Anvin, Will Deacon
Zhenzhong Duan <zhenzhong.duan@oracle.com> writes:
> On 2019/10/13 17:02, Vitaly Kuznetsov wrote:
>> Zhenzhong Duan <zhenzhong.duan@oracle.com> writes:
> ...snip
>> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
>> index ef836d6..6e14bd4 100644
>> --- a/arch/x86/kernel/kvm.c
>> +++ b/arch/x86/kernel/kvm.c
>> @@ -825,18 +825,31 @@ __visible bool __kvm_vcpu_is_preempted(long cpu)
>> */
>> void __init kvm_spinlock_init(void)
>> {
>> - /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
>> - if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
>> + /*
>> + * Disable PV qspinlocks if host kernel doesn't support
>> + * KVM_FEATURE_PV_UNHALT feature or there is only 1 vCPU.
>> + * virt_spin_lock_key is enabled to avoid lock holder
>> + * preemption issue.
>> + */
>> + if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT) ||
>> + num_possible_cpus() == 1) {
>> + pr_info("PV spinlocks disabled\n");
>> Why don't we need static_branch_disable(&virt_spin_lock_key) here?
>
> Thanks for review.
>
> I have a brief explanation in above comment area.
>
> Boris also raised the same question in v4 and see my detailed explanation
>
> in https://lkml.org/lkml/2019/10/6/39
>
>>
>> Also, as you're printing the exact reason for PV spinlocks disablement
>> in other cases, I'd suggest separating "no host support" and "single
>> CPU" cases.
>
> Will do after reaching a consensus on your first question.
Oh, sorry I missed v4 discussion. As I'm not the first to ask why we
don't do static_branch_disable(&virt_spin_lock_key) here I suggest we do
the followin:
- Split !kvm_para_has_feature(KVM_FEATURE_PV_UNHALT) and
num_possible_cpus() == 1 cases
- Do static_branch_disable(&virt_spin_lock_key) for UP case (just for
consistency).
- Add a comment why we don't do that for
!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT) case (basically, what you
replied to Boris)
This will also allow us to print the exact reason.
>
>>
>>> return;
>>> + }
>>>
>>> if (kvm_para_has_hint(KVM_HINTS_REALTIME)) {
>>> + pr_info("PV spinlocks disabled with KVM_HINTS_REALTIME hints.\n");
>>> static_branch_disable(&virt_spin_lock_key);
>>> return;
>>> }
>>>
>>> - /* Don't use the pvqspinlock code if there is only 1 vCPU. */
>>> - if (num_possible_cpus() == 1)
>>> + if (nopvspin) {
>>> + pr_info("PV spinlocks disabled forced by \"nopvspin\" parameter.\n");
>> Nit: to make it sound better a comma is missing between 'disabled' and
>> 'forced', or
>>
>> "PV spinlocks forcefully disabled by ..." if you prefer.
>
> Will do.
>
> Zhenzhong
>
>
--
Vitaly
^ permalink raw reply [flat|nested] 13+ messages in thread
end of thread, other threads:[~2019-10-14 9:18 UTC | newest]
Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-10-07 9:04 [PATCH v5 0/5] Add a unified parameter "nopvspin" Zhenzhong Duan
2019-10-07 9:04 ` [PATCH v5 1/5] Revert "KVM: X86: Fix setup the virt_spin_lock_key before static key get initialized" Zhenzhong Duan
2019-10-13 9:08 ` Vitaly Kuznetsov
2019-10-07 9:04 ` [PATCH v5 2/5] x86/kvm: Change print code to use pr_*() format Zhenzhong Duan
2019-10-13 9:06 ` Vitaly Kuznetsov
2019-10-14 1:38 ` Zhenzhong Duan
2019-10-07 9:04 ` [PATCH v5 3/5] x86/kvm: Add "nopvspin" parameter to disable PV spinlocks Zhenzhong Duan
2019-10-13 9:02 ` Vitaly Kuznetsov
2019-10-14 1:52 ` Zhenzhong Duan
2019-10-14 9:18 ` Vitaly Kuznetsov
2019-10-07 9:04 ` [PATCH v5 4/5] xen: Mark "xen_nopvspin" parameter obsolete Zhenzhong Duan
2019-10-07 9:04 ` [PATCH v5 5/5] x86/hyperv: Mark "hv_nopvspin" " Zhenzhong Duan
2019-10-12 8:40 ` [PATCH v5 0/5] Add a unified parameter "nopvspin" Zhenzhong Duan
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