Re: [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is_preempted()
Hi Bibo, kernel test robot noticed the following build errors: [auto build test ERROR on 6a23ae0a96a600d1d12557add110e0bb6e32730c] url: https://github.com/intel-lab-lkp/linux/commits/Bibo-Mao/LoongArch-KVM-Add-preempt-hint-feature-in-hypervisor-side/20251118-161212 base: 6a23ae0a96a600d1d12557add110e0bb6e32730c patch link: https://lore.kernel.org/r/20251118080656.2012805-3-maobibo%40loongson.cn patch subject: [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is_preempted() config: loongarch-randconfig-r052-20251120 (https://download.01.org/0day-ci/archive/20251120/[email protected]/config) compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff) reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251120/[email protected]/reproduce) If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot | Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/ All errors (new ones prefixed by >>): >> arch/loongarch/kernel/paravirt.c:346:14: error: redefinition of >> 'vcpu_is_preempted' 346 | bool notrace vcpu_is_preempted(int cpu) | ^ include/linux/sched.h:2263:20: note: previous definition is here 2263 | static inline bool vcpu_is_preempted(int cpu) |^ >> arch/loongarch/kernel/paravirt.c:348:9: error: use of undeclared identifier >> 'mp_ops' 348 | return mp_ops.vcpu_is_preempted(cpu); |^ 2 errors generated. vim +/vcpu_is_preempted +346 arch/loongarch/kernel/paravirt.c 345 > 346 bool notrace vcpu_is_preempted(int cpu) 347 { > 348 return mp_ops.vcpu_is_preempted(cpu); -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
Re: [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is_preempted()
On Wed, Nov 19, 2025 at 2:12 PM Bibo Mao wrote:
>
>
>
> On 2025/11/19 上午9:59, Bibo Mao wrote:
> >
> >
> > On 2025/11/18 下午8:48, Huacai Chen wrote:
> >> Hi, Bibo,
> >>
> >> On Tue, Nov 18, 2025 at 4:07 PM Bibo Mao wrote:
> >>>
> >>> Function vcpu_is_preempted() is used to check whether vCPU is preempted
> >>> or not. Here add implementation with vcpu_is_preempted() when option
> >>> CONFIG_PARAVIRT is enabled.
> >>>
> >>> Signed-off-by: Bibo Mao
> >>> ---
> >>> arch/loongarch/include/asm/smp.h | 1 +
> >>> arch/loongarch/include/asm/spinlock.h | 5 +
> >>> arch/loongarch/kernel/paravirt.c | 16
> >>> arch/loongarch/kernel/smp.c | 6 ++
> >>> 4 files changed, 28 insertions(+)
> >>>
> >>> diff --git a/arch/loongarch/include/asm/smp.h
> >>> b/arch/loongarch/include/asm/smp.h
> >>> index 3a47f52959a8..5b37f7bf2060 100644
> >>> --- a/arch/loongarch/include/asm/smp.h
> >>> +++ b/arch/loongarch/include/asm/smp.h
> >>> @@ -18,6 +18,7 @@ struct smp_ops {
> >>> void (*init_ipi)(void);
> >>> void (*send_ipi_single)(int cpu, unsigned int action);
> >>> void (*send_ipi_mask)(const struct cpumask *mask, unsigned
> >>> int action);
> >>> + bool (*vcpu_is_preempted)(int cpu);
> >>> };
> >>> extern struct smp_ops mp_ops;
> >>>
> >>> diff --git a/arch/loongarch/include/asm/spinlock.h
> >>> b/arch/loongarch/include/asm/spinlock.h
> >>> index 7cb3476999be..c001cef893aa 100644
> >>> --- a/arch/loongarch/include/asm/spinlock.h
> >>> +++ b/arch/loongarch/include/asm/spinlock.h
> >>> @@ -5,6 +5,11 @@
> >>> #ifndef _ASM_SPINLOCK_H
> >>> #define _ASM_SPINLOCK_H
> >>>
> >>> +#ifdef CONFIG_PARAVIRT
> >>> +#define vcpu_is_preempted vcpu_is_preempted
> >>> +bool vcpu_is_preempted(int cpu);
> >>> +#endif
> >> Maybe paravirt.h is a better place?
> >
> > It is actually a little strange to add macro CONFIG_PARAVIRT in file
> > asm/spinlock.h
> >
> > vcpu_is_preempted is originally defined in header file
> > include/linux/sched.h like this
> > #ifndef vcpu_is_preempted
> > static inline bool vcpu_is_preempted(int cpu)
> > {
> > return false;
> > }
> > #endif
> >
> > that requires that header file is included before sched.h, file
> > asm/spinlock.h can meet this requirement, however header file paravirt.h
> > maybe it is not included before sched.h in generic.
> >
> > Here vcpu_is_preempted definition is added before the following including.
> > #include
> > #include
> > #include
> > Maybe it is better to be added after the above header files including
> > sentences, but need further investigation.
> >>
> >>> +
> >>> #include
> >>> #include
> >>> #include
> >>> diff --git a/arch/loongarch/kernel/paravirt.c
> >>> b/arch/loongarch/kernel/paravirt.c
> >>> index b1b51f920b23..b99404b6b13f 100644
> >>> --- a/arch/loongarch/kernel/paravirt.c
> >>> +++ b/arch/loongarch/kernel/paravirt.c
> >>> @@ -52,6 +52,13 @@ static u64 paravt_steal_clock(int cpu)
> >>> #ifdef CONFIG_SMP
> >>> static struct smp_ops native_ops;
> >>>
> >>> +static bool pv_vcpu_is_preempted(int cpu)
> >>> +{
> >>> + struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
> >>> +
> >>> + return !!(src->preempted & KVM_VCPU_PREEMPTED);
> >>> +}
> >>> +
> >>> static void pv_send_ipi_single(int cpu, unsigned int action)
> >>> {
> >>> int min, old;
> >>> @@ -308,6 +315,9 @@ int __init pv_time_init(void)
> >>> pr_err("Failed to install cpu hotplug callbacks\n");
> >>> return r;
> >>> }
> >>> +
> >>> + if (kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
> >>> + mp_ops.vcpu_is_preempted = pv_vcpu_is_preempted;
> >>> #endif
> >>>
> >>> static_call_update(pv_steal_clock, paravt_steal_clock);
> >>> @@ -332,3 +342,9 @@ int __init pv_spinlock_init(void)
> >>>
> >>> return 0;
> >>> }
> >>> +
> >>> +bool notrace vcpu_is_preempted(int cpu)
> >>> +{
> >>> + return mp_ops.vcpu_is_preempted(cpu);
> >>> +}
> >>
> >> We can simplify the whole patch like this, then we don't need to touch
> >> smp.c, and we can merge Patch-2/3.
> >>
> >> +bool notrace vcpu_is_preempted(int cpu)
> >> +{
> >> + if (!kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
> >> + return false;
> >> + else {
> >> + struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
> >> + return !!(src->preempted & KVM_VCPU_PREEMPTED);
> >> + }
> >> +}
> > 1. there is assembly output about relative vcpu_is_preempted
> > :
> > move$r4,$r0
> > jirl$r0,$r1,0
> >
> > :
> > pcalau12i $r13,8759(0x2237)
> > slli.d $r4,$r4,0x3
> > addi.d $r13,$r13,-1000(0xc18)
> > ldx.d $r13,$r13,$r4
> > pcalau12i $r12,5462(0x1556)
> > addi.d $r12,$r12,384(0x180)
> > add.d $r12,$r13,$r12
> > ld.bu $r4,$r12,16(0x10)
> > andi$r4,$r4,0x1
> > jirl$r0,
Re: [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is_preempted()
On Wed, Nov 19, 2025 at 10:53 AM Bibo Mao wrote:
>
>
>
> On 2025/11/18 下午8:48, Huacai Chen wrote:
> > Hi, Bibo,
> >
> > On Tue, Nov 18, 2025 at 4:07 PM Bibo Mao wrote:
> >>
> >> Function vcpu_is_preempted() is used to check whether vCPU is preempted
> >> or not. Here add implementation with vcpu_is_preempted() when option
> >> CONFIG_PARAVIRT is enabled.
> >>
> >> Signed-off-by: Bibo Mao
> >> ---
> >> arch/loongarch/include/asm/smp.h | 1 +
> >> arch/loongarch/include/asm/spinlock.h | 5 +
> >> arch/loongarch/kernel/paravirt.c | 16
> >> arch/loongarch/kernel/smp.c | 6 ++
> >> 4 files changed, 28 insertions(+)
> >>
> >> diff --git a/arch/loongarch/include/asm/smp.h
> >> b/arch/loongarch/include/asm/smp.h
> >> index 3a47f52959a8..5b37f7bf2060 100644
> >> --- a/arch/loongarch/include/asm/smp.h
> >> +++ b/arch/loongarch/include/asm/smp.h
> >> @@ -18,6 +18,7 @@ struct smp_ops {
> >> void (*init_ipi)(void);
> >> void (*send_ipi_single)(int cpu, unsigned int action);
> >> void (*send_ipi_mask)(const struct cpumask *mask, unsigned int
> >> action);
> >> + bool (*vcpu_is_preempted)(int cpu);
> >> };
> >> extern struct smp_ops mp_ops;
> >>
> >> diff --git a/arch/loongarch/include/asm/spinlock.h
> >> b/arch/loongarch/include/asm/spinlock.h
> >> index 7cb3476999be..c001cef893aa 100644
> >> --- a/arch/loongarch/include/asm/spinlock.h
> >> +++ b/arch/loongarch/include/asm/spinlock.h
> >> @@ -5,6 +5,11 @@
> >> #ifndef _ASM_SPINLOCK_H
> >> #define _ASM_SPINLOCK_H
> >>
> >> +#ifdef CONFIG_PARAVIRT
> >> +#define vcpu_is_preempted vcpu_is_preempted
> >> +bool vcpu_is_preempted(int cpu);
> >> +#endif
> > Maybe paravirt.h is a better place?
> how about put it in asm/qspinlock.h since it is included by header file
> asm/spinlock.h already?
qspinlock.h is better than spinlock.h
Huacai
>
> >
> >> +
> >> #include
> >> #include
> >> #include
> >> diff --git a/arch/loongarch/kernel/paravirt.c
> >> b/arch/loongarch/kernel/paravirt.c
> >> index b1b51f920b23..b99404b6b13f 100644
> >> --- a/arch/loongarch/kernel/paravirt.c
> >> +++ b/arch/loongarch/kernel/paravirt.c
> >> @@ -52,6 +52,13 @@ static u64 paravt_steal_clock(int cpu)
> >> #ifdef CONFIG_SMP
> >> static struct smp_ops native_ops;
> >>
> >> +static bool pv_vcpu_is_preempted(int cpu)
> >> +{
> >> + struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
> >> +
> >> + return !!(src->preempted & KVM_VCPU_PREEMPTED);
> >> +}
> >> +
> >> static void pv_send_ipi_single(int cpu, unsigned int action)
> >> {
> >> int min, old;
> >> @@ -308,6 +315,9 @@ int __init pv_time_init(void)
> >> pr_err("Failed to install cpu hotplug callbacks\n");
> >> return r;
> >> }
> >> +
> >> + if (kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
> >> + mp_ops.vcpu_is_preempted = pv_vcpu_is_preempted;
> >> #endif
> >>
> >> static_call_update(pv_steal_clock, paravt_steal_clock);
> >> @@ -332,3 +342,9 @@ int __init pv_spinlock_init(void)
> >>
> >> return 0;
> >> }
> >> +
> >> +bool notrace vcpu_is_preempted(int cpu)
> >> +{
> >> + return mp_ops.vcpu_is_preempted(cpu);
> >> +}
> >
> > We can simplify the whole patch like this, then we don't need to touch
> > smp.c, and we can merge Patch-2/3.
> >
> > +bool notrace vcpu_is_preempted(int cpu)
> > +{
> > + if (!kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
> > + return false;
> > + else {
> > + struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
> > + return !!(src->preempted & KVM_VCPU_PREEMPTED);
> > + }
> > +}
> > Huacai
> >
> >> +EXPORT_SYMBOL(vcpu_is_preempted);
> >> diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
> >> index 46036d98da75..f04192fedf8d 100644
> >> --- a/arch/loongarch/kernel/smp.c
> >> +++ b/arch/loongarch/kernel/smp.c
> >> @@ -307,10 +307,16 @@ static void loongson_init_ipi(void)
> >> panic("IPI IRQ request failed\n");
> >> }
> >>
> >> +static bool loongson_vcpu_is_preempted(int cpu)
> >> +{
> >> + return false;
> >> +}
> >> +
> >> struct smp_ops mp_ops = {
> >> .init_ipi = loongson_init_ipi,
> >> .send_ipi_single= loongson_send_ipi_single,
> >> .send_ipi_mask = loongson_send_ipi_mask,
> >> + .vcpu_is_preempted = loongson_vcpu_is_preempted,
> >> };
> >>
> >> static void __init fdt_smp_setup(void)
> >> --
> >> 2.39.3
> >>
> >>
>
>
Re: [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is_preempted()
On 2025/11/19 上午9:59, Bibo Mao wrote:
On 2025/11/18 下午8:48, Huacai Chen wrote:
Hi, Bibo,
On Tue, Nov 18, 2025 at 4:07 PM Bibo Mao wrote:
Function vcpu_is_preempted() is used to check whether vCPU is preempted
or not. Here add implementation with vcpu_is_preempted() when option
CONFIG_PARAVIRT is enabled.
Signed-off-by: Bibo Mao
---
arch/loongarch/include/asm/smp.h | 1 +
arch/loongarch/include/asm/spinlock.h | 5 +
arch/loongarch/kernel/paravirt.c | 16
arch/loongarch/kernel/smp.c | 6 ++
4 files changed, 28 insertions(+)
diff --git a/arch/loongarch/include/asm/smp.h
b/arch/loongarch/include/asm/smp.h
index 3a47f52959a8..5b37f7bf2060 100644
--- a/arch/loongarch/include/asm/smp.h
+++ b/arch/loongarch/include/asm/smp.h
@@ -18,6 +18,7 @@ struct smp_ops {
void (*init_ipi)(void);
void (*send_ipi_single)(int cpu, unsigned int action);
void (*send_ipi_mask)(const struct cpumask *mask, unsigned
int action);
+ bool (*vcpu_is_preempted)(int cpu);
};
extern struct smp_ops mp_ops;
diff --git a/arch/loongarch/include/asm/spinlock.h
b/arch/loongarch/include/asm/spinlock.h
index 7cb3476999be..c001cef893aa 100644
--- a/arch/loongarch/include/asm/spinlock.h
+++ b/arch/loongarch/include/asm/spinlock.h
@@ -5,6 +5,11 @@
#ifndef _ASM_SPINLOCK_H
#define _ASM_SPINLOCK_H
+#ifdef CONFIG_PARAVIRT
+#define vcpu_is_preempted vcpu_is_preempted
+bool vcpu_is_preempted(int cpu);
+#endif
Maybe paravirt.h is a better place?
It is actually a little strange to add macro CONFIG_PARAVIRT in file
asm/spinlock.h
vcpu_is_preempted is originally defined in header file
include/linux/sched.h like this
#ifndef vcpu_is_preempted
static inline bool vcpu_is_preempted(int cpu)
{
return false;
}
#endif
that requires that header file is included before sched.h, file
asm/spinlock.h can meet this requirement, however header file paravirt.h
maybe it is not included before sched.h in generic.
Here vcpu_is_preempted definition is added before the following including.
#include
#include
#include
Maybe it is better to be added after the above header files including
sentences, but need further investigation.
+
#include
#include
#include
diff --git a/arch/loongarch/kernel/paravirt.c
b/arch/loongarch/kernel/paravirt.c
index b1b51f920b23..b99404b6b13f 100644
--- a/arch/loongarch/kernel/paravirt.c
+++ b/arch/loongarch/kernel/paravirt.c
@@ -52,6 +52,13 @@ static u64 paravt_steal_clock(int cpu)
#ifdef CONFIG_SMP
static struct smp_ops native_ops;
+static bool pv_vcpu_is_preempted(int cpu)
+{
+ struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
+
+ return !!(src->preempted & KVM_VCPU_PREEMPTED);
+}
+
static void pv_send_ipi_single(int cpu, unsigned int action)
{
int min, old;
@@ -308,6 +315,9 @@ int __init pv_time_init(void)
pr_err("Failed to install cpu hotplug callbacks\n");
return r;
}
+
+ if (kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
+ mp_ops.vcpu_is_preempted = pv_vcpu_is_preempted;
#endif
static_call_update(pv_steal_clock, paravt_steal_clock);
@@ -332,3 +342,9 @@ int __init pv_spinlock_init(void)
return 0;
}
+
+bool notrace vcpu_is_preempted(int cpu)
+{
+ return mp_ops.vcpu_is_preempted(cpu);
+}
We can simplify the whole patch like this, then we don't need to touch
smp.c, and we can merge Patch-2/3.
+bool notrace vcpu_is_preempted(int cpu)
+{
+ if (!kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
+ return false;
+ else {
+ struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
+ return !!(src->preempted & KVM_VCPU_PREEMPTED);
+ }
+}
1. there is assembly output about relative vcpu_is_preempted
:
move $r4,$r0
jirl $r0,$r1,0
:
pcalau12i $r13,8759(0x2237)
slli.d $r4,$r4,0x3
addi.d $r13,$r13,-1000(0xc18)
ldx.d $r13,$r13,$r4
pcalau12i $r12,5462(0x1556)
addi.d $r12,$r12,384(0x180)
add.d $r12,$r13,$r12
ld.bu $r4,$r12,16(0x10)
andi $r4,$r4,0x1
jirl $r0,$r1,0
:
pcalau12i $r12,8775(0x2247)
ld.d $r12,$r12,-472(0xe28)
jirl $r0,$r12,0
andi $r0,$r0,0x0
:
pcalau12i $r12,8151(0x1fd7)
ld.d $r12,$r12,-1008(0xc10)
bstrpick.d $r12,$r12,0x1a,0x1a
beqz $r12,188(0xbc) # 9024ec60
pcalau12i $r12,11802(0x2e1a)
addi.d $r12,$r12,-1400(0xa88)
ldptr.w $r14,$r12,36(0x24)
beqz $r14,108(0x6c) # 9024ec20
addi.w $r13,$r0,1(0x1)
bne $r14,$r13,164(0xa4) # 9024ec60
ldptr.w $r13,$r12,40(0x28)
bnez $r13,24(0x18) # 9024ebdc
lu12i.w $r14,262144(0x4)
ori $r14,$r14,0x4
cp
Re: [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is_preempted()
On 2025/11/19 上午10:58, Huacai Chen wrote:
On Wed, Nov 19, 2025 at 10:01 AM Bibo Mao wrote:
On 2025/11/18 下午8:48, Huacai Chen wrote:
Hi, Bibo,
On Tue, Nov 18, 2025 at 4:07 PM Bibo Mao wrote:
Function vcpu_is_preempted() is used to check whether vCPU is preempted
or not. Here add implementation with vcpu_is_preempted() when option
CONFIG_PARAVIRT is enabled.
Signed-off-by: Bibo Mao
---
arch/loongarch/include/asm/smp.h | 1 +
arch/loongarch/include/asm/spinlock.h | 5 +
arch/loongarch/kernel/paravirt.c | 16
arch/loongarch/kernel/smp.c | 6 ++
4 files changed, 28 insertions(+)
diff --git a/arch/loongarch/include/asm/smp.h b/arch/loongarch/include/asm/smp.h
index 3a47f52959a8..5b37f7bf2060 100644
--- a/arch/loongarch/include/asm/smp.h
+++ b/arch/loongarch/include/asm/smp.h
@@ -18,6 +18,7 @@ struct smp_ops {
void (*init_ipi)(void);
void (*send_ipi_single)(int cpu, unsigned int action);
void (*send_ipi_mask)(const struct cpumask *mask, unsigned int
action);
+ bool (*vcpu_is_preempted)(int cpu);
};
extern struct smp_ops mp_ops;
diff --git a/arch/loongarch/include/asm/spinlock.h
b/arch/loongarch/include/asm/spinlock.h
index 7cb3476999be..c001cef893aa 100644
--- a/arch/loongarch/include/asm/spinlock.h
+++ b/arch/loongarch/include/asm/spinlock.h
@@ -5,6 +5,11 @@
#ifndef _ASM_SPINLOCK_H
#define _ASM_SPINLOCK_H
+#ifdef CONFIG_PARAVIRT
+#define vcpu_is_preempted vcpu_is_preempted
+bool vcpu_is_preempted(int cpu);
+#endif
Maybe paravirt.h is a better place?
It is actually a little strange to add macro CONFIG_PARAVIRT in file
asm/spinlock.h
vcpu_is_preempted is originally defined in header file
include/linux/sched.h like this
#ifndef vcpu_is_preempted
static inline bool vcpu_is_preempted(int cpu)
{
return false;
}
#endif
that requires that header file is included before sched.h, file
asm/spinlock.h can meet this requirement, however header file paravirt.h
maybe it is not included before sched.h in generic.
Here vcpu_is_preempted definition is added before the following including.
#include
#include
#include
Maybe it is better to be added after the above header files including
sentences, but need further investigation.
powerpc put it in paravirt.h, so I think it is possible.
paravirt.h is included by header file asm/qspinlock.h on powerpc,
however it is not so on loongarch :)
# grep paravirt.h arch/powerpc/* -r
arch/powerpc/include/asm/paravirt_api_clock.h:#include
arch/powerpc/include/asm/qspinlock.h:#include
arch/powerpc/include/asm/simple_spinlock.h:#include
$ grep paravirt.h arch/loongarch/* -r
arch/loongarch/include/asm/paravirt_api_clock.h:#include
+
#include
#include
#include
diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
index b1b51f920b23..b99404b6b13f 100644
--- a/arch/loongarch/kernel/paravirt.c
+++ b/arch/loongarch/kernel/paravirt.c
@@ -52,6 +52,13 @@ static u64 paravt_steal_clock(int cpu)
#ifdef CONFIG_SMP
static struct smp_ops native_ops;
+static bool pv_vcpu_is_preempted(int cpu)
+{
+ struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
+
+ return !!(src->preempted & KVM_VCPU_PREEMPTED);
+}
+
static void pv_send_ipi_single(int cpu, unsigned int action)
{
int min, old;
@@ -308,6 +315,9 @@ int __init pv_time_init(void)
pr_err("Failed to install cpu hotplug callbacks\n");
return r;
}
+
+ if (kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
+ mp_ops.vcpu_is_preempted = pv_vcpu_is_preempted;
#endif
static_call_update(pv_steal_clock, paravt_steal_clock);
@@ -332,3 +342,9 @@ int __init pv_spinlock_init(void)
return 0;
}
+
+bool notrace vcpu_is_preempted(int cpu)
+{
+ return mp_ops.vcpu_is_preempted(cpu);
+}
We can simplify the whole patch like this, then we don't need to touch
smp.c, and we can merge Patch-2/3.
+bool notrace vcpu_is_preempted(int cpu)
+{
+ if (!kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
+ return false;
+ else {
+ struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
+ return !!(src->preempted & KVM_VCPU_PREEMPTED);
+ }
+}
1. there is assembly output about relative vcpu_is_preempted
:
move$r4,$r0
jirl$r0,$r1,0
:
pcalau12i $r13,8759(0x2237)
slli.d $r4,$r4,0x3
addi.d $r13,$r13,-1000(0xc18)
ldx.d $r13,$r13,$r4
pcalau12i $r12,5462(0x1556)
addi.d $r12,$r12,384(0x180)
add.d $r12,$r13,$r12
ld.bu $r4,$r12,16(0x10)
andi$r4,$r4,0x1
jirl$r0,$r1,0
:
pcalau12i $r12,8775(0x2247)
ld.d$r12,$r12,-472(0xe28)
jirl$r0,$r12,0
andi$r0,$r0,0x0
:
pcalau12i $r12,8151(0x1fd7)
ld
Re: [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is_preempted()
On Wed, Nov 19, 2025 at 10:01 AM Bibo Mao wrote:
>
>
>
> On 2025/11/18 下午8:48, Huacai Chen wrote:
> > Hi, Bibo,
> >
> > On Tue, Nov 18, 2025 at 4:07 PM Bibo Mao wrote:
> >>
> >> Function vcpu_is_preempted() is used to check whether vCPU is preempted
> >> or not. Here add implementation with vcpu_is_preempted() when option
> >> CONFIG_PARAVIRT is enabled.
> >>
> >> Signed-off-by: Bibo Mao
> >> ---
> >> arch/loongarch/include/asm/smp.h | 1 +
> >> arch/loongarch/include/asm/spinlock.h | 5 +
> >> arch/loongarch/kernel/paravirt.c | 16
> >> arch/loongarch/kernel/smp.c | 6 ++
> >> 4 files changed, 28 insertions(+)
> >>
> >> diff --git a/arch/loongarch/include/asm/smp.h
> >> b/arch/loongarch/include/asm/smp.h
> >> index 3a47f52959a8..5b37f7bf2060 100644
> >> --- a/arch/loongarch/include/asm/smp.h
> >> +++ b/arch/loongarch/include/asm/smp.h
> >> @@ -18,6 +18,7 @@ struct smp_ops {
> >> void (*init_ipi)(void);
> >> void (*send_ipi_single)(int cpu, unsigned int action);
> >> void (*send_ipi_mask)(const struct cpumask *mask, unsigned int
> >> action);
> >> + bool (*vcpu_is_preempted)(int cpu);
> >> };
> >> extern struct smp_ops mp_ops;
> >>
> >> diff --git a/arch/loongarch/include/asm/spinlock.h
> >> b/arch/loongarch/include/asm/spinlock.h
> >> index 7cb3476999be..c001cef893aa 100644
> >> --- a/arch/loongarch/include/asm/spinlock.h
> >> +++ b/arch/loongarch/include/asm/spinlock.h
> >> @@ -5,6 +5,11 @@
> >> #ifndef _ASM_SPINLOCK_H
> >> #define _ASM_SPINLOCK_H
> >>
> >> +#ifdef CONFIG_PARAVIRT
> >> +#define vcpu_is_preempted vcpu_is_preempted
> >> +bool vcpu_is_preempted(int cpu);
> >> +#endif
> > Maybe paravirt.h is a better place?
>
> It is actually a little strange to add macro CONFIG_PARAVIRT in file
> asm/spinlock.h
>
> vcpu_is_preempted is originally defined in header file
> include/linux/sched.h like this
> #ifndef vcpu_is_preempted
> static inline bool vcpu_is_preempted(int cpu)
> {
> return false;
> }
> #endif
>
> that requires that header file is included before sched.h, file
> asm/spinlock.h can meet this requirement, however header file paravirt.h
> maybe it is not included before sched.h in generic.
>
> Here vcpu_is_preempted definition is added before the following including.
> #include
> #include
> #include
> Maybe it is better to be added after the above header files including
> sentences, but need further investigation.
powerpc put it in paravirt.h, so I think it is possible.
> >
> >> +
> >> #include
> >> #include
> >> #include
> >> diff --git a/arch/loongarch/kernel/paravirt.c
> >> b/arch/loongarch/kernel/paravirt.c
> >> index b1b51f920b23..b99404b6b13f 100644
> >> --- a/arch/loongarch/kernel/paravirt.c
> >> +++ b/arch/loongarch/kernel/paravirt.c
> >> @@ -52,6 +52,13 @@ static u64 paravt_steal_clock(int cpu)
> >> #ifdef CONFIG_SMP
> >> static struct smp_ops native_ops;
> >>
> >> +static bool pv_vcpu_is_preempted(int cpu)
> >> +{
> >> + struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
> >> +
> >> + return !!(src->preempted & KVM_VCPU_PREEMPTED);
> >> +}
> >> +
> >> static void pv_send_ipi_single(int cpu, unsigned int action)
> >> {
> >> int min, old;
> >> @@ -308,6 +315,9 @@ int __init pv_time_init(void)
> >> pr_err("Failed to install cpu hotplug callbacks\n");
> >> return r;
> >> }
> >> +
> >> + if (kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
> >> + mp_ops.vcpu_is_preempted = pv_vcpu_is_preempted;
> >> #endif
> >>
> >> static_call_update(pv_steal_clock, paravt_steal_clock);
> >> @@ -332,3 +342,9 @@ int __init pv_spinlock_init(void)
> >>
> >> return 0;
> >> }
> >> +
> >> +bool notrace vcpu_is_preempted(int cpu)
> >> +{
> >> + return mp_ops.vcpu_is_preempted(cpu);
> >> +}
> >
> > We can simplify the whole patch like this, then we don't need to touch
> > smp.c, and we can merge Patch-2/3.
> >
> > +bool notrace vcpu_is_preempted(int cpu)
> > +{
> > + if (!kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
> > + return false;
> > + else {
> > + struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
> > + return !!(src->preempted & KVM_VCPU_PREEMPTED);
> > + }
> > +}
> 1. there is assembly output about relative vcpu_is_preempted
> :
> move$r4,$r0
> jirl$r0,$r1,0
>
> :
> pcalau12i $r13,8759(0x2237)
> slli.d $r4,$r4,0x3
> addi.d $r13,$r13,-1000(0xc18)
> ldx.d $r13,$r13,$r4
> pcalau12i $r12,5462(0x1556)
> addi.d $r12,$r12,384(0x180)
> add.d $r12,$r13,$r12
> ld.bu $r4,$r12,16(0x10)
> andi$r4,$r4,0x1
> jirl$r0,$r1,0
>
> :
> pcalau12i $r12,8775(0x2247)
> ld.d$r12,$r12,-472(0xe28)
> jirl$r0,$r12,0
> andi$r0,$r0,0x0
>
>
Re: [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is_preempted()
On 2025/11/18 下午8:48, Huacai Chen wrote:
Hi, Bibo,
On Tue, Nov 18, 2025 at 4:07 PM Bibo Mao wrote:
Function vcpu_is_preempted() is used to check whether vCPU is preempted
or not. Here add implementation with vcpu_is_preempted() when option
CONFIG_PARAVIRT is enabled.
Signed-off-by: Bibo Mao
---
arch/loongarch/include/asm/smp.h | 1 +
arch/loongarch/include/asm/spinlock.h | 5 +
arch/loongarch/kernel/paravirt.c | 16
arch/loongarch/kernel/smp.c | 6 ++
4 files changed, 28 insertions(+)
diff --git a/arch/loongarch/include/asm/smp.h b/arch/loongarch/include/asm/smp.h
index 3a47f52959a8..5b37f7bf2060 100644
--- a/arch/loongarch/include/asm/smp.h
+++ b/arch/loongarch/include/asm/smp.h
@@ -18,6 +18,7 @@ struct smp_ops {
void (*init_ipi)(void);
void (*send_ipi_single)(int cpu, unsigned int action);
void (*send_ipi_mask)(const struct cpumask *mask, unsigned int action);
+ bool (*vcpu_is_preempted)(int cpu);
};
extern struct smp_ops mp_ops;
diff --git a/arch/loongarch/include/asm/spinlock.h
b/arch/loongarch/include/asm/spinlock.h
index 7cb3476999be..c001cef893aa 100644
--- a/arch/loongarch/include/asm/spinlock.h
+++ b/arch/loongarch/include/asm/spinlock.h
@@ -5,6 +5,11 @@
#ifndef _ASM_SPINLOCK_H
#define _ASM_SPINLOCK_H
+#ifdef CONFIG_PARAVIRT
+#define vcpu_is_preempted vcpu_is_preempted
+bool vcpu_is_preempted(int cpu);
+#endif
Maybe paravirt.h is a better place?
how about put it in asm/qspinlock.h since it is included by header file
asm/spinlock.h already?
+
#include
#include
#include
diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
index b1b51f920b23..b99404b6b13f 100644
--- a/arch/loongarch/kernel/paravirt.c
+++ b/arch/loongarch/kernel/paravirt.c
@@ -52,6 +52,13 @@ static u64 paravt_steal_clock(int cpu)
#ifdef CONFIG_SMP
static struct smp_ops native_ops;
+static bool pv_vcpu_is_preempted(int cpu)
+{
+ struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
+
+ return !!(src->preempted & KVM_VCPU_PREEMPTED);
+}
+
static void pv_send_ipi_single(int cpu, unsigned int action)
{
int min, old;
@@ -308,6 +315,9 @@ int __init pv_time_init(void)
pr_err("Failed to install cpu hotplug callbacks\n");
return r;
}
+
+ if (kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
+ mp_ops.vcpu_is_preempted = pv_vcpu_is_preempted;
#endif
static_call_update(pv_steal_clock, paravt_steal_clock);
@@ -332,3 +342,9 @@ int __init pv_spinlock_init(void)
return 0;
}
+
+bool notrace vcpu_is_preempted(int cpu)
+{
+ return mp_ops.vcpu_is_preempted(cpu);
+}
We can simplify the whole patch like this, then we don't need to touch
smp.c, and we can merge Patch-2/3.
+bool notrace vcpu_is_preempted(int cpu)
+{
+ if (!kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
+ return false;
+ else {
+ struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
+ return !!(src->preempted & KVM_VCPU_PREEMPTED);
+ }
+}
Huacai
+EXPORT_SYMBOL(vcpu_is_preempted);
diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
index 46036d98da75..f04192fedf8d 100644
--- a/arch/loongarch/kernel/smp.c
+++ b/arch/loongarch/kernel/smp.c
@@ -307,10 +307,16 @@ static void loongson_init_ipi(void)
panic("IPI IRQ request failed\n");
}
+static bool loongson_vcpu_is_preempted(int cpu)
+{
+ return false;
+}
+
struct smp_ops mp_ops = {
.init_ipi = loongson_init_ipi,
.send_ipi_single= loongson_send_ipi_single,
.send_ipi_mask = loongson_send_ipi_mask,
+ .vcpu_is_preempted = loongson_vcpu_is_preempted,
};
static void __init fdt_smp_setup(void)
--
2.39.3
Re: [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is_preempted()
On 2025/11/18 下午8:48, Huacai Chen wrote:
Hi, Bibo,
On Tue, Nov 18, 2025 at 4:07 PM Bibo Mao wrote:
Function vcpu_is_preempted() is used to check whether vCPU is preempted
or not. Here add implementation with vcpu_is_preempted() when option
CONFIG_PARAVIRT is enabled.
Signed-off-by: Bibo Mao
---
arch/loongarch/include/asm/smp.h | 1 +
arch/loongarch/include/asm/spinlock.h | 5 +
arch/loongarch/kernel/paravirt.c | 16
arch/loongarch/kernel/smp.c | 6 ++
4 files changed, 28 insertions(+)
diff --git a/arch/loongarch/include/asm/smp.h b/arch/loongarch/include/asm/smp.h
index 3a47f52959a8..5b37f7bf2060 100644
--- a/arch/loongarch/include/asm/smp.h
+++ b/arch/loongarch/include/asm/smp.h
@@ -18,6 +18,7 @@ struct smp_ops {
void (*init_ipi)(void);
void (*send_ipi_single)(int cpu, unsigned int action);
void (*send_ipi_mask)(const struct cpumask *mask, unsigned int action);
+ bool (*vcpu_is_preempted)(int cpu);
};
extern struct smp_ops mp_ops;
diff --git a/arch/loongarch/include/asm/spinlock.h
b/arch/loongarch/include/asm/spinlock.h
index 7cb3476999be..c001cef893aa 100644
--- a/arch/loongarch/include/asm/spinlock.h
+++ b/arch/loongarch/include/asm/spinlock.h
@@ -5,6 +5,11 @@
#ifndef _ASM_SPINLOCK_H
#define _ASM_SPINLOCK_H
+#ifdef CONFIG_PARAVIRT
+#define vcpu_is_preempted vcpu_is_preempted
+bool vcpu_is_preempted(int cpu);
+#endif
Maybe paravirt.h is a better place?
It is actually a little strange to add macro CONFIG_PARAVIRT in file
asm/spinlock.h
vcpu_is_preempted is originally defined in header file
include/linux/sched.h like this
#ifndef vcpu_is_preempted
static inline bool vcpu_is_preempted(int cpu)
{
return false;
}
#endif
that requires that header file is included before sched.h, file
asm/spinlock.h can meet this requirement, however header file paravirt.h
maybe it is not included before sched.h in generic.
Here vcpu_is_preempted definition is added before the following including.
#include
#include
#include
Maybe it is better to be added after the above header files including
sentences, but need further investigation.
+
#include
#include
#include
diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
index b1b51f920b23..b99404b6b13f 100644
--- a/arch/loongarch/kernel/paravirt.c
+++ b/arch/loongarch/kernel/paravirt.c
@@ -52,6 +52,13 @@ static u64 paravt_steal_clock(int cpu)
#ifdef CONFIG_SMP
static struct smp_ops native_ops;
+static bool pv_vcpu_is_preempted(int cpu)
+{
+ struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
+
+ return !!(src->preempted & KVM_VCPU_PREEMPTED);
+}
+
static void pv_send_ipi_single(int cpu, unsigned int action)
{
int min, old;
@@ -308,6 +315,9 @@ int __init pv_time_init(void)
pr_err("Failed to install cpu hotplug callbacks\n");
return r;
}
+
+ if (kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
+ mp_ops.vcpu_is_preempted = pv_vcpu_is_preempted;
#endif
static_call_update(pv_steal_clock, paravt_steal_clock);
@@ -332,3 +342,9 @@ int __init pv_spinlock_init(void)
return 0;
}
+
+bool notrace vcpu_is_preempted(int cpu)
+{
+ return mp_ops.vcpu_is_preempted(cpu);
+}
We can simplify the whole patch like this, then we don't need to touch
smp.c, and we can merge Patch-2/3.
+bool notrace vcpu_is_preempted(int cpu)
+{
+ if (!kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
+ return false;
+ else {
+ struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
+ return !!(src->preempted & KVM_VCPU_PREEMPTED);
+ }
+}
1. there is assembly output about relative vcpu_is_preempted
:
move$r4,$r0
jirl$r0,$r1,0
:
pcalau12i $r13,8759(0x2237)
slli.d $r4,$r4,0x3
addi.d $r13,$r13,-1000(0xc18)
ldx.d $r13,$r13,$r4
pcalau12i $r12,5462(0x1556)
addi.d $r12,$r12,384(0x180)
add.d $r12,$r13,$r12
ld.bu $r4,$r12,16(0x10)
andi$r4,$r4,0x1
jirl$r0,$r1,0
:
pcalau12i $r12,8775(0x2247)
ld.d$r12,$r12,-472(0xe28)
jirl$r0,$r12,0
andi$r0,$r0,0x0
:
pcalau12i $r12,8151(0x1fd7)
ld.d$r12,$r12,-1008(0xc10)
bstrpick.d $r12,$r12,0x1a,0x1a
beqz$r12,188(0xbc) # 9024ec60
pcalau12i $r12,11802(0x2e1a)
addi.d $r12,$r12,-1400(0xa88)
ldptr.w $r14,$r12,36(0x24)
beqz$r14,108(0x6c) # 9024ec20
addi.w $r13,$r0,1(0x1)
bne $r14,$r13,164(0xa4) # 9024ec60
ldptr.w $r13,$r12,40(0x28)
bnez$r13,24(0x18) # 9024ebdc
lu12i.w $r14,262144(0x4)
ori $r14,$r14,0x4
cpucfg $r14,$r14
slli.w $r13,$r14,0x0
st.w$r14,$r12,40(0x28)
Re: [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is_preempted()
Hi, Bibo,
On Tue, Nov 18, 2025 at 4:07 PM Bibo Mao wrote:
>
> Function vcpu_is_preempted() is used to check whether vCPU is preempted
> or not. Here add implementation with vcpu_is_preempted() when option
> CONFIG_PARAVIRT is enabled.
>
> Signed-off-by: Bibo Mao
> ---
> arch/loongarch/include/asm/smp.h | 1 +
> arch/loongarch/include/asm/spinlock.h | 5 +
> arch/loongarch/kernel/paravirt.c | 16
> arch/loongarch/kernel/smp.c | 6 ++
> 4 files changed, 28 insertions(+)
>
> diff --git a/arch/loongarch/include/asm/smp.h
> b/arch/loongarch/include/asm/smp.h
> index 3a47f52959a8..5b37f7bf2060 100644
> --- a/arch/loongarch/include/asm/smp.h
> +++ b/arch/loongarch/include/asm/smp.h
> @@ -18,6 +18,7 @@ struct smp_ops {
> void (*init_ipi)(void);
> void (*send_ipi_single)(int cpu, unsigned int action);
> void (*send_ipi_mask)(const struct cpumask *mask, unsigned int
> action);
> + bool (*vcpu_is_preempted)(int cpu);
> };
> extern struct smp_ops mp_ops;
>
> diff --git a/arch/loongarch/include/asm/spinlock.h
> b/arch/loongarch/include/asm/spinlock.h
> index 7cb3476999be..c001cef893aa 100644
> --- a/arch/loongarch/include/asm/spinlock.h
> +++ b/arch/loongarch/include/asm/spinlock.h
> @@ -5,6 +5,11 @@
> #ifndef _ASM_SPINLOCK_H
> #define _ASM_SPINLOCK_H
>
> +#ifdef CONFIG_PARAVIRT
> +#define vcpu_is_preempted vcpu_is_preempted
> +bool vcpu_is_preempted(int cpu);
> +#endif
Maybe paravirt.h is a better place?
> +
> #include
> #include
> #include
> diff --git a/arch/loongarch/kernel/paravirt.c
> b/arch/loongarch/kernel/paravirt.c
> index b1b51f920b23..b99404b6b13f 100644
> --- a/arch/loongarch/kernel/paravirt.c
> +++ b/arch/loongarch/kernel/paravirt.c
> @@ -52,6 +52,13 @@ static u64 paravt_steal_clock(int cpu)
> #ifdef CONFIG_SMP
> static struct smp_ops native_ops;
>
> +static bool pv_vcpu_is_preempted(int cpu)
> +{
> + struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
> +
> + return !!(src->preempted & KVM_VCPU_PREEMPTED);
> +}
> +
> static void pv_send_ipi_single(int cpu, unsigned int action)
> {
> int min, old;
> @@ -308,6 +315,9 @@ int __init pv_time_init(void)
> pr_err("Failed to install cpu hotplug callbacks\n");
> return r;
> }
> +
> + if (kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
> + mp_ops.vcpu_is_preempted = pv_vcpu_is_preempted;
> #endif
>
> static_call_update(pv_steal_clock, paravt_steal_clock);
> @@ -332,3 +342,9 @@ int __init pv_spinlock_init(void)
>
> return 0;
> }
> +
> +bool notrace vcpu_is_preempted(int cpu)
> +{
> + return mp_ops.vcpu_is_preempted(cpu);
> +}
We can simplify the whole patch like this, then we don't need to touch
smp.c, and we can merge Patch-2/3.
+bool notrace vcpu_is_preempted(int cpu)
+{
+ if (!kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
+ return false;
+ else {
+ struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
+ return !!(src->preempted & KVM_VCPU_PREEMPTED);
+ }
+}
Huacai
> +EXPORT_SYMBOL(vcpu_is_preempted);
> diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
> index 46036d98da75..f04192fedf8d 100644
> --- a/arch/loongarch/kernel/smp.c
> +++ b/arch/loongarch/kernel/smp.c
> @@ -307,10 +307,16 @@ static void loongson_init_ipi(void)
> panic("IPI IRQ request failed\n");
> }
>
> +static bool loongson_vcpu_is_preempted(int cpu)
> +{
> + return false;
> +}
> +
> struct smp_ops mp_ops = {
> .init_ipi = loongson_init_ipi,
> .send_ipi_single= loongson_send_ipi_single,
> .send_ipi_mask = loongson_send_ipi_mask,
> + .vcpu_is_preempted = loongson_vcpu_is_preempted,
> };
>
> static void __init fdt_smp_setup(void)
> --
> 2.39.3
>
>
