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
Includes asm/hypervisor.h in order to reference x86_hyper_type.
Signed-off-by: Zhenzhong Duan <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: "K. Y. Srinivasan" <[email protected]>
Cc: Haiyang Zhang <[email protected]>
Cc: Stephen Hemminger <[email protected]>
Cc: Sasha Levin <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
---
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
Fix stale description of "xen_nopvspin" as we use qspinlock now.
Signed-off-by: Zhenzhong Duan <[email protected]>
Reviewed-by: Juergen Gross <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Stefano Stabellini <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
---
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
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 <[email protected]>
Signed-off-by: Zhenzhong Duan <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krcmar <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Jim Mattson <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
---
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 <[email protected]>
*/
+#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
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 <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krcmar <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Jim Mattson <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Will Deacon <[email protected]>
---
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
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 <[email protected]>
> Cc: Jonathan Corbet <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Radim Krcmar <[email protected]>
> Cc: Sean Christopherson <[email protected]>
> Cc: Vitaly Kuznetsov <[email protected]>
> Cc: Wanpeng Li <[email protected]>
> Cc: Jim Mattson <[email protected]>
> Cc: Joerg Roedel <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Will Deacon <[email protected]>
> ---
> 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
>
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 <[email protected]>
This wasn't really suggested by Vitaly, he just requested it be done in a
separate patch.
> Signed-off-by: Zhenzhong Duan <[email protected]>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Radim Krcmar <[email protected]>
> Cc: Sean Christopherson <[email protected]>
> Cc: Vitaly Kuznetsov <[email protected]>
> Cc: Wanpeng Li <[email protected]>
> Cc: Jim Mattson <[email protected]>
> Cc: Joerg Roedel <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> ---
> 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 <[email protected]>
> */
>
> +#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
>
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 <[email protected]>
> Reviewed-by: Juergen Gross <[email protected]>
> Cc: Jonathan Corbet <[email protected]>
> Cc: Boris Ostrovsky <[email protected]>
> Cc: Juergen Gross <[email protected]>
> Cc: Stefano Stabellini <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> ---
> 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
>
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 <[email protected]>
> Cc: Jonathan Corbet <[email protected]>
> Cc: "K. Y. Srinivasan" <[email protected]>
> Cc: Haiyang Zhang <[email protected]>
> Cc: Stephen Hemminger <[email protected]>
> Cc: Sasha Levin <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> ---
> 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
>
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 <[email protected]>
......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
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<[email protected]>
> This wasn't really suggested by Vitaly, he just requested it be done in a
> separate patch.
Will fix.
>
>> Signed-off-by: Zhenzhong Duan<[email protected]>
>> Cc: Paolo Bonzini<[email protected]>
>> Cc: Radim Krcmar<[email protected]>
>> Cc: Sean Christopherson<[email protected]>
>> Cc: Vitaly Kuznetsov<[email protected]>
>> Cc: Wanpeng Li<[email protected]>
>> Cc: Jim Mattson<[email protected]>
>> Cc: Joerg Roedel<[email protected]>
>> Cc: Thomas Gleixner<[email protected]>
>> Cc: Ingo Molnar<[email protected]>
>> Cc: Borislav Petkov<[email protected]>
>> Cc: "H. Peter Anvin"<[email protected]>
>> ---
>> 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<[email protected]>
>> */
>>
>> +#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
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 <[email protected]>
>> Cc: Jonathan Corbet <[email protected]>
>> Cc: "K. Y. Srinivasan" <[email protected]>
>> Cc: Haiyang Zhang <[email protected]>
>> Cc: Stephen Hemminger <[email protected]>
>> Cc: Sasha Levin <[email protected]>
>> Cc: Thomas Gleixner <[email protected]>
>> Cc: Ingo Molnar <[email protected]>
>> Cc: Borislav Petkov <[email protected]>
>> Cc: "H. Peter Anvin" <[email protected]>
>> ---
...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
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<[email protected]>
>> Reviewed-by: Juergen Gross<[email protected]>
>> Cc: Jonathan Corbet<[email protected]>
>> Cc: Boris Ostrovsky<[email protected]>
>> Cc: Juergen Gross<[email protected]>
>> Cc: Stefano Stabellini<[email protected]>
>> Cc: Thomas Gleixner<[email protected]>
>> Cc: Ingo Molnar<[email protected]>
>> Cc: Borislav Petkov<[email protected]>
>> Cc: "H. Peter Anvin"<[email protected]>
>> ---
...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