FPU is lazy enabled with KVM hypervisor. After FPU is enabled and
loaded, vCPU can be preempted and FPU will be lost again. Here FPU
is delay load until guest enter entry.
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
---
arch/loongarch/include/asm/kvm_host.h | 2 ++
arch/loongarch/kvm/exit.c | 15 ++++++++----
arch/loongarch/kvm/vcpu.c | 33 +++++++++++++++++----------
3 files changed, 33 insertions(+), 17 deletions(-)
diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
index e4fe5b8e8149..902ff7bc0e35 100644
--- a/arch/loongarch/include/asm/kvm_host.h
+++ b/arch/loongarch/include/asm/kvm_host.h
@@ -37,6 +37,7 @@
#define KVM_REQ_TLB_FLUSH_GPA KVM_ARCH_REQ(0)
#define KVM_REQ_STEAL_UPDATE KVM_ARCH_REQ(1)
#define KVM_REQ_PMU KVM_ARCH_REQ(2)
+#define KVM_REQ_FPU_LOAD KVM_ARCH_REQ(3)
#define KVM_GUESTDBG_SW_BP_MASK \
(KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)
@@ -234,6 +235,7 @@ struct kvm_vcpu_arch {
u64 vpid;
gpa_t flush_gpa;
+ int fpu_load_type;
/* Frequency of stable timer in Hz */
u64 timer_mhz;
ktime_t expire;
diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
index 74b427287e96..b6f08df8fedb 100644
--- a/arch/loongarch/kvm/exit.c
+++ b/arch/loongarch/kvm/exit.c
@@ -754,7 +754,8 @@ static int kvm_handle_fpu_disabled(struct kvm_vcpu *vcpu, int ecode)
return RESUME_HOST;
}
- kvm_own_fpu(vcpu);
+ vcpu->arch.fpu_load_type = KVM_LARCH_FPU;
+ kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
return RESUME_GUEST;
}
@@ -794,8 +795,10 @@ static int kvm_handle_lsx_disabled(struct kvm_vcpu *vcpu, int ecode)
{
if (!kvm_guest_has_lsx(&vcpu->arch))
kvm_queue_exception(vcpu, EXCCODE_INE, 0);
- else
- kvm_own_lsx(vcpu);
+ else {
+ vcpu->arch.fpu_load_type = KVM_LARCH_LSX;
+ kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
+ }
return RESUME_GUEST;
}
@@ -812,8 +815,10 @@ static int kvm_handle_lasx_disabled(struct kvm_vcpu *vcpu, int ecode)
{
if (!kvm_guest_has_lasx(&vcpu->arch))
kvm_queue_exception(vcpu, EXCCODE_INE, 0);
- else
- kvm_own_lasx(vcpu);
+ else {
+ vcpu->arch.fpu_load_type = KVM_LARCH_LASX;
+ kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
+ }
return RESUME_GUEST;
}
diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index d91a1160a309..3e749e9738b2 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -232,6 +232,27 @@ static void kvm_late_check_requests(struct kvm_vcpu *vcpu)
kvm_flush_tlb_gpa(vcpu, vcpu->arch.flush_gpa);
vcpu->arch.flush_gpa = INVALID_GPA;
}
+
+ if (kvm_check_request(KVM_REQ_FPU_LOAD, vcpu)) {
+ switch (vcpu->arch.fpu_load_type) {
+ case KVM_LARCH_FPU:
+ kvm_own_fpu(vcpu);
+ break;
+
+ case KVM_LARCH_LSX:
+ kvm_own_lsx(vcpu);
+ break;
+
+ case KVM_LARCH_LASX:
+ kvm_own_lasx(vcpu);
+ break;
+
+ default:
+ break;
+ }
+
+ vcpu->arch.fpu_load_type = 0;
+ }
}
/*
@@ -1338,8 +1359,6 @@ static inline void kvm_check_fcsr_alive(struct kvm_vcpu *vcpu) { }
/* Enable FPU and restore context */
void kvm_own_fpu(struct kvm_vcpu *vcpu)
{
- preempt_disable();
-
/*
* Enable FPU for guest
* Set FR and FRE according to guest context
@@ -1350,16 +1369,12 @@ void kvm_own_fpu(struct kvm_vcpu *vcpu)
kvm_restore_fpu(&vcpu->arch.fpu);
vcpu->arch.aux_inuse |= KVM_LARCH_FPU;
trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_FPU);
-
- preempt_enable();
}
#ifdef CONFIG_CPU_HAS_LSX
/* Enable LSX and restore context */
int kvm_own_lsx(struct kvm_vcpu *vcpu)
{
- preempt_disable();
-
/* Enable LSX for guest */
kvm_check_fcsr(vcpu, vcpu->arch.fpu.fcsr);
set_csr_euen(CSR_EUEN_LSXEN | CSR_EUEN_FPEN);
@@ -1381,8 +1396,6 @@ int kvm_own_lsx(struct kvm_vcpu *vcpu)
trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_LSX);
vcpu->arch.aux_inuse |= KVM_LARCH_LSX | KVM_LARCH_FPU;
- preempt_enable();
-
return 0;
}
#endif
@@ -1391,8 +1404,6 @@ int kvm_own_lsx(struct kvm_vcpu *vcpu)
/* Enable LASX and restore context */
int kvm_own_lasx(struct kvm_vcpu *vcpu)
{
- preempt_disable();
-
kvm_check_fcsr(vcpu, vcpu->arch.fpu.fcsr);
set_csr_euen(CSR_EUEN_FPEN | CSR_EUEN_LSXEN | CSR_EUEN_LASXEN);
switch (vcpu->arch.aux_inuse & (KVM_LARCH_FPU | KVM_LARCH_LSX)) {
@@ -1414,8 +1425,6 @@ int kvm_own_lasx(struct kvm_vcpu *vcpu)
trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_LASX);
vcpu->arch.aux_inuse |= KVM_LARCH_LASX | KVM_LARCH_LSX | KVM_LARCH_FPU;
- preempt_enable();
-
return 0;
}
#endif
--
2.39.3Hi, Bibo,
On Tue, Jan 27, 2026 at 8:51 PM Bibo Mao <maobibo@loongson.cn> wrote:
>
> FPU is lazy enabled with KVM hypervisor. After FPU is enabled and
> loaded, vCPU can be preempted and FPU will be lost again. Here FPU
> is delay load until guest enter entry.
>
> Signed-off-by: Bibo Mao <maobibo@loongson.cn>
> ---
> arch/loongarch/include/asm/kvm_host.h | 2 ++
> arch/loongarch/kvm/exit.c | 15 ++++++++----
> arch/loongarch/kvm/vcpu.c | 33 +++++++++++++++++----------
> 3 files changed, 33 insertions(+), 17 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
> index e4fe5b8e8149..902ff7bc0e35 100644
> --- a/arch/loongarch/include/asm/kvm_host.h
> +++ b/arch/loongarch/include/asm/kvm_host.h
> @@ -37,6 +37,7 @@
> #define KVM_REQ_TLB_FLUSH_GPA KVM_ARCH_REQ(0)
> #define KVM_REQ_STEAL_UPDATE KVM_ARCH_REQ(1)
> #define KVM_REQ_PMU KVM_ARCH_REQ(2)
> +#define KVM_REQ_FPU_LOAD KVM_ARCH_REQ(3)
>
> #define KVM_GUESTDBG_SW_BP_MASK \
> (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)
> @@ -234,6 +235,7 @@ struct kvm_vcpu_arch {
> u64 vpid;
> gpa_t flush_gpa;
>
> + int fpu_load_type;
I think the logic of V1 is better, it doesn't increase the size of
kvm_vcpu_arch, and the constant checking is a little faster than
variable checking.
Huacai
> /* Frequency of stable timer in Hz */
> u64 timer_mhz;
> ktime_t expire;
> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
> index 74b427287e96..b6f08df8fedb 100644
> --- a/arch/loongarch/kvm/exit.c
> +++ b/arch/loongarch/kvm/exit.c
> @@ -754,7 +754,8 @@ static int kvm_handle_fpu_disabled(struct kvm_vcpu *vcpu, int ecode)
> return RESUME_HOST;
> }
>
> - kvm_own_fpu(vcpu);
> + vcpu->arch.fpu_load_type = KVM_LARCH_FPU;
> + kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
>
> return RESUME_GUEST;
> }
> @@ -794,8 +795,10 @@ static int kvm_handle_lsx_disabled(struct kvm_vcpu *vcpu, int ecode)
> {
> if (!kvm_guest_has_lsx(&vcpu->arch))
> kvm_queue_exception(vcpu, EXCCODE_INE, 0);
> - else
> - kvm_own_lsx(vcpu);
> + else {
> + vcpu->arch.fpu_load_type = KVM_LARCH_LSX;
> + kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
> + }
>
> return RESUME_GUEST;
> }
> @@ -812,8 +815,10 @@ static int kvm_handle_lasx_disabled(struct kvm_vcpu *vcpu, int ecode)
> {
> if (!kvm_guest_has_lasx(&vcpu->arch))
> kvm_queue_exception(vcpu, EXCCODE_INE, 0);
> - else
> - kvm_own_lasx(vcpu);
> + else {
> + vcpu->arch.fpu_load_type = KVM_LARCH_LASX;
> + kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
> + }
>
> return RESUME_GUEST;
> }
> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> index d91a1160a309..3e749e9738b2 100644
> --- a/arch/loongarch/kvm/vcpu.c
> +++ b/arch/loongarch/kvm/vcpu.c
> @@ -232,6 +232,27 @@ static void kvm_late_check_requests(struct kvm_vcpu *vcpu)
> kvm_flush_tlb_gpa(vcpu, vcpu->arch.flush_gpa);
> vcpu->arch.flush_gpa = INVALID_GPA;
> }
> +
> + if (kvm_check_request(KVM_REQ_FPU_LOAD, vcpu)) {
> + switch (vcpu->arch.fpu_load_type) {
> + case KVM_LARCH_FPU:
> + kvm_own_fpu(vcpu);
> + break;
> +
> + case KVM_LARCH_LSX:
> + kvm_own_lsx(vcpu);
> + break;
> +
> + case KVM_LARCH_LASX:
> + kvm_own_lasx(vcpu);
> + break;
> +
> + default:
> + break;
> + }
> +
> + vcpu->arch.fpu_load_type = 0;
> + }
> }
>
> /*
> @@ -1338,8 +1359,6 @@ static inline void kvm_check_fcsr_alive(struct kvm_vcpu *vcpu) { }
> /* Enable FPU and restore context */
> void kvm_own_fpu(struct kvm_vcpu *vcpu)
> {
> - preempt_disable();
> -
> /*
> * Enable FPU for guest
> * Set FR and FRE according to guest context
> @@ -1350,16 +1369,12 @@ void kvm_own_fpu(struct kvm_vcpu *vcpu)
> kvm_restore_fpu(&vcpu->arch.fpu);
> vcpu->arch.aux_inuse |= KVM_LARCH_FPU;
> trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_FPU);
> -
> - preempt_enable();
> }
>
> #ifdef CONFIG_CPU_HAS_LSX
> /* Enable LSX and restore context */
> int kvm_own_lsx(struct kvm_vcpu *vcpu)
> {
> - preempt_disable();
> -
> /* Enable LSX for guest */
> kvm_check_fcsr(vcpu, vcpu->arch.fpu.fcsr);
> set_csr_euen(CSR_EUEN_LSXEN | CSR_EUEN_FPEN);
> @@ -1381,8 +1396,6 @@ int kvm_own_lsx(struct kvm_vcpu *vcpu)
>
> trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_LSX);
> vcpu->arch.aux_inuse |= KVM_LARCH_LSX | KVM_LARCH_FPU;
> - preempt_enable();
> -
> return 0;
> }
> #endif
> @@ -1391,8 +1404,6 @@ int kvm_own_lsx(struct kvm_vcpu *vcpu)
> /* Enable LASX and restore context */
> int kvm_own_lasx(struct kvm_vcpu *vcpu)
> {
> - preempt_disable();
> -
> kvm_check_fcsr(vcpu, vcpu->arch.fpu.fcsr);
> set_csr_euen(CSR_EUEN_FPEN | CSR_EUEN_LSXEN | CSR_EUEN_LASXEN);
> switch (vcpu->arch.aux_inuse & (KVM_LARCH_FPU | KVM_LARCH_LSX)) {
> @@ -1414,8 +1425,6 @@ int kvm_own_lasx(struct kvm_vcpu *vcpu)
>
> trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_LASX);
> vcpu->arch.aux_inuse |= KVM_LARCH_LASX | KVM_LARCH_LSX | KVM_LARCH_FPU;
> - preempt_enable();
> -
> return 0;
> }
> #endif
> --
> 2.39.3
>
>
On 2026/1/28 下午12:05, Huacai Chen wrote:
> Hi, Bibo,
>
> On Tue, Jan 27, 2026 at 8:51 PM Bibo Mao <maobibo@loongson.cn> wrote:
>>
>> FPU is lazy enabled with KVM hypervisor. After FPU is enabled and
>> loaded, vCPU can be preempted and FPU will be lost again. Here FPU
>> is delay load until guest enter entry.
>>
>> Signed-off-by: Bibo Mao <maobibo@loongson.cn>
>> ---
>> arch/loongarch/include/asm/kvm_host.h | 2 ++
>> arch/loongarch/kvm/exit.c | 15 ++++++++----
>> arch/loongarch/kvm/vcpu.c | 33 +++++++++++++++++----------
>> 3 files changed, 33 insertions(+), 17 deletions(-)
>>
>> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
>> index e4fe5b8e8149..902ff7bc0e35 100644
>> --- a/arch/loongarch/include/asm/kvm_host.h
>> +++ b/arch/loongarch/include/asm/kvm_host.h
>> @@ -37,6 +37,7 @@
>> #define KVM_REQ_TLB_FLUSH_GPA KVM_ARCH_REQ(0)
>> #define KVM_REQ_STEAL_UPDATE KVM_ARCH_REQ(1)
>> #define KVM_REQ_PMU KVM_ARCH_REQ(2)
>> +#define KVM_REQ_FPU_LOAD KVM_ARCH_REQ(3)
>>
>> #define KVM_GUESTDBG_SW_BP_MASK \
>> (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)
>> @@ -234,6 +235,7 @@ struct kvm_vcpu_arch {
>> u64 vpid;
>> gpa_t flush_gpa;
>>
>> + int fpu_load_type;
> I think the logic of V1 is better, it doesn't increase the size of
> kvm_vcpu_arch, and the constant checking is a little faster than
> variable checking.
The main reason is that FPU_LOAD request is not so frequent, there is
atomic instruction in kvm_check_request() and the unconditional
kvm_check_request() may be unnecessary, also there will LBT LOAD check
in later version.
So I think one unconditional atomic test_and_clear may be better than
three/four atomic test_and_clear.
kvm_check_request(KVM_REQ_FPU_LOAD,vcpu)
kvm_check_request(KVM_REQ_FPU_LSX, vcpu)
kvm_check_request(KVM_REQ_FPU_LASX, vcpu)
Actually different people have different view about this :)
Regards
Bibo Mao
>
> Huacai
>
>> /* Frequency of stable timer in Hz */
>> u64 timer_mhz;
>> ktime_t expire;
>> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
>> index 74b427287e96..b6f08df8fedb 100644
>> --- a/arch/loongarch/kvm/exit.c
>> +++ b/arch/loongarch/kvm/exit.c
>> @@ -754,7 +754,8 @@ static int kvm_handle_fpu_disabled(struct kvm_vcpu *vcpu, int ecode)
>> return RESUME_HOST;
>> }
>>
>> - kvm_own_fpu(vcpu);
>> + vcpu->arch.fpu_load_type = KVM_LARCH_FPU;
>> + kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
>>
>> return RESUME_GUEST;
>> }
>> @@ -794,8 +795,10 @@ static int kvm_handle_lsx_disabled(struct kvm_vcpu *vcpu, int ecode)
>> {
>> if (!kvm_guest_has_lsx(&vcpu->arch))
>> kvm_queue_exception(vcpu, EXCCODE_INE, 0);
>> - else
>> - kvm_own_lsx(vcpu);
>> + else {
>> + vcpu->arch.fpu_load_type = KVM_LARCH_LSX;
>> + kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
>> + }
>>
>> return RESUME_GUEST;
>> }
>> @@ -812,8 +815,10 @@ static int kvm_handle_lasx_disabled(struct kvm_vcpu *vcpu, int ecode)
>> {
>> if (!kvm_guest_has_lasx(&vcpu->arch))
>> kvm_queue_exception(vcpu, EXCCODE_INE, 0);
>> - else
>> - kvm_own_lasx(vcpu);
>> + else {
>> + vcpu->arch.fpu_load_type = KVM_LARCH_LASX;
>> + kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
>> + }
>>
>> return RESUME_GUEST;
>> }
>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
>> index d91a1160a309..3e749e9738b2 100644
>> --- a/arch/loongarch/kvm/vcpu.c
>> +++ b/arch/loongarch/kvm/vcpu.c
>> @@ -232,6 +232,27 @@ static void kvm_late_check_requests(struct kvm_vcpu *vcpu)
>> kvm_flush_tlb_gpa(vcpu, vcpu->arch.flush_gpa);
>> vcpu->arch.flush_gpa = INVALID_GPA;
>> }
>> +
>> + if (kvm_check_request(KVM_REQ_FPU_LOAD, vcpu)) {
>> + switch (vcpu->arch.fpu_load_type) {
>> + case KVM_LARCH_FPU:
>> + kvm_own_fpu(vcpu);
>> + break;
>> +
>> + case KVM_LARCH_LSX:
>> + kvm_own_lsx(vcpu);
>> + break;
>> +
>> + case KVM_LARCH_LASX:
>> + kvm_own_lasx(vcpu);
>> + break;
>> +
>> + default:
>> + break;
>> + }
>> +
>> + vcpu->arch.fpu_load_type = 0;
>> + }
>> }
>>
>> /*
>> @@ -1338,8 +1359,6 @@ static inline void kvm_check_fcsr_alive(struct kvm_vcpu *vcpu) { }
>> /* Enable FPU and restore context */
>> void kvm_own_fpu(struct kvm_vcpu *vcpu)
>> {
>> - preempt_disable();
>> -
>> /*
>> * Enable FPU for guest
>> * Set FR and FRE according to guest context
>> @@ -1350,16 +1369,12 @@ void kvm_own_fpu(struct kvm_vcpu *vcpu)
>> kvm_restore_fpu(&vcpu->arch.fpu);
>> vcpu->arch.aux_inuse |= KVM_LARCH_FPU;
>> trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_FPU);
>> -
>> - preempt_enable();
>> }
>>
>> #ifdef CONFIG_CPU_HAS_LSX
>> /* Enable LSX and restore context */
>> int kvm_own_lsx(struct kvm_vcpu *vcpu)
>> {
>> - preempt_disable();
>> -
>> /* Enable LSX for guest */
>> kvm_check_fcsr(vcpu, vcpu->arch.fpu.fcsr);
>> set_csr_euen(CSR_EUEN_LSXEN | CSR_EUEN_FPEN);
>> @@ -1381,8 +1396,6 @@ int kvm_own_lsx(struct kvm_vcpu *vcpu)
>>
>> trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_LSX);
>> vcpu->arch.aux_inuse |= KVM_LARCH_LSX | KVM_LARCH_FPU;
>> - preempt_enable();
>> -
>> return 0;
>> }
>> #endif
>> @@ -1391,8 +1404,6 @@ int kvm_own_lsx(struct kvm_vcpu *vcpu)
>> /* Enable LASX and restore context */
>> int kvm_own_lasx(struct kvm_vcpu *vcpu)
>> {
>> - preempt_disable();
>> -
>> kvm_check_fcsr(vcpu, vcpu->arch.fpu.fcsr);
>> set_csr_euen(CSR_EUEN_FPEN | CSR_EUEN_LSXEN | CSR_EUEN_LASXEN);
>> switch (vcpu->arch.aux_inuse & (KVM_LARCH_FPU | KVM_LARCH_LSX)) {
>> @@ -1414,8 +1425,6 @@ int kvm_own_lasx(struct kvm_vcpu *vcpu)
>>
>> trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_LASX);
>> vcpu->arch.aux_inuse |= KVM_LARCH_LASX | KVM_LARCH_LSX | KVM_LARCH_FPU;
>> - preempt_enable();
>> -
>> return 0;
>> }
>> #endif
>> --
>> 2.39.3
>>
>>
On Wed, Jan 28, 2026 at 2:35 PM Bibo Mao <maobibo@loongson.cn> wrote:
>
>
>
> On 2026/1/28 下午12:05, Huacai Chen wrote:
> > Hi, Bibo,
> >
> > On Tue, Jan 27, 2026 at 8:51 PM Bibo Mao <maobibo@loongson.cn> wrote:
> >>
> >> FPU is lazy enabled with KVM hypervisor. After FPU is enabled and
> >> loaded, vCPU can be preempted and FPU will be lost again. Here FPU
> >> is delay load until guest enter entry.
> >>
> >> Signed-off-by: Bibo Mao <maobibo@loongson.cn>
> >> ---
> >> arch/loongarch/include/asm/kvm_host.h | 2 ++
> >> arch/loongarch/kvm/exit.c | 15 ++++++++----
> >> arch/loongarch/kvm/vcpu.c | 33 +++++++++++++++++----------
> >> 3 files changed, 33 insertions(+), 17 deletions(-)
> >>
> >> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
> >> index e4fe5b8e8149..902ff7bc0e35 100644
> >> --- a/arch/loongarch/include/asm/kvm_host.h
> >> +++ b/arch/loongarch/include/asm/kvm_host.h
> >> @@ -37,6 +37,7 @@
> >> #define KVM_REQ_TLB_FLUSH_GPA KVM_ARCH_REQ(0)
> >> #define KVM_REQ_STEAL_UPDATE KVM_ARCH_REQ(1)
> >> #define KVM_REQ_PMU KVM_ARCH_REQ(2)
> >> +#define KVM_REQ_FPU_LOAD KVM_ARCH_REQ(3)
> >>
> >> #define KVM_GUESTDBG_SW_BP_MASK \
> >> (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)
> >> @@ -234,6 +235,7 @@ struct kvm_vcpu_arch {
> >> u64 vpid;
> >> gpa_t flush_gpa;
> >>
> >> + int fpu_load_type;
> > I think the logic of V1 is better, it doesn't increase the size of
> > kvm_vcpu_arch, and the constant checking is a little faster than
> > variable checking.
> The main reason is that FPU_LOAD request is not so frequent, there is
> atomic instruction in kvm_check_request() and the unconditional
> kvm_check_request() may be unnecessary, also there will LBT LOAD check
> in later version.
>
> So I think one unconditional atomic test_and_clear may be better than
> three/four atomic test_and_clear.
> kvm_check_request(KVM_REQ_FPU_LOAD,vcpu)
> kvm_check_request(KVM_REQ_FPU_LSX, vcpu)
> kvm_check_request(KVM_REQ_FPU_LASX, vcpu)
>
> Actually different people have different view about this :)
Depends on how complex kvm_check_request() is. If it is very complex,
checking once and following a switch-case is better.
Huacai
>
> Regards
> Bibo Mao
> >
> > Huacai
> >
> >> /* Frequency of stable timer in Hz */
> >> u64 timer_mhz;
> >> ktime_t expire;
> >> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
> >> index 74b427287e96..b6f08df8fedb 100644
> >> --- a/arch/loongarch/kvm/exit.c
> >> +++ b/arch/loongarch/kvm/exit.c
> >> @@ -754,7 +754,8 @@ static int kvm_handle_fpu_disabled(struct kvm_vcpu *vcpu, int ecode)
> >> return RESUME_HOST;
> >> }
> >>
> >> - kvm_own_fpu(vcpu);
> >> + vcpu->arch.fpu_load_type = KVM_LARCH_FPU;
> >> + kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
> >>
> >> return RESUME_GUEST;
> >> }
> >> @@ -794,8 +795,10 @@ static int kvm_handle_lsx_disabled(struct kvm_vcpu *vcpu, int ecode)
> >> {
> >> if (!kvm_guest_has_lsx(&vcpu->arch))
> >> kvm_queue_exception(vcpu, EXCCODE_INE, 0);
> >> - else
> >> - kvm_own_lsx(vcpu);
> >> + else {
> >> + vcpu->arch.fpu_load_type = KVM_LARCH_LSX;
> >> + kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
> >> + }
> >>
> >> return RESUME_GUEST;
> >> }
> >> @@ -812,8 +815,10 @@ static int kvm_handle_lasx_disabled(struct kvm_vcpu *vcpu, int ecode)
> >> {
> >> if (!kvm_guest_has_lasx(&vcpu->arch))
> >> kvm_queue_exception(vcpu, EXCCODE_INE, 0);
> >> - else
> >> - kvm_own_lasx(vcpu);
> >> + else {
> >> + vcpu->arch.fpu_load_type = KVM_LARCH_LASX;
> >> + kvm_make_request(KVM_REQ_FPU_LOAD, vcpu);
> >> + }
> >>
> >> return RESUME_GUEST;
> >> }
> >> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> >> index d91a1160a309..3e749e9738b2 100644
> >> --- a/arch/loongarch/kvm/vcpu.c
> >> +++ b/arch/loongarch/kvm/vcpu.c
> >> @@ -232,6 +232,27 @@ static void kvm_late_check_requests(struct kvm_vcpu *vcpu)
> >> kvm_flush_tlb_gpa(vcpu, vcpu->arch.flush_gpa);
> >> vcpu->arch.flush_gpa = INVALID_GPA;
> >> }
> >> +
> >> + if (kvm_check_request(KVM_REQ_FPU_LOAD, vcpu)) {
> >> + switch (vcpu->arch.fpu_load_type) {
> >> + case KVM_LARCH_FPU:
> >> + kvm_own_fpu(vcpu);
> >> + break;
> >> +
> >> + case KVM_LARCH_LSX:
> >> + kvm_own_lsx(vcpu);
> >> + break;
> >> +
> >> + case KVM_LARCH_LASX:
> >> + kvm_own_lasx(vcpu);
> >> + break;
> >> +
> >> + default:
> >> + break;
> >> + }
> >> +
> >> + vcpu->arch.fpu_load_type = 0;
> >> + }
> >> }
> >>
> >> /*
> >> @@ -1338,8 +1359,6 @@ static inline void kvm_check_fcsr_alive(struct kvm_vcpu *vcpu) { }
> >> /* Enable FPU and restore context */
> >> void kvm_own_fpu(struct kvm_vcpu *vcpu)
> >> {
> >> - preempt_disable();
> >> -
> >> /*
> >> * Enable FPU for guest
> >> * Set FR and FRE according to guest context
> >> @@ -1350,16 +1369,12 @@ void kvm_own_fpu(struct kvm_vcpu *vcpu)
> >> kvm_restore_fpu(&vcpu->arch.fpu);
> >> vcpu->arch.aux_inuse |= KVM_LARCH_FPU;
> >> trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_FPU);
> >> -
> >> - preempt_enable();
> >> }
> >>
> >> #ifdef CONFIG_CPU_HAS_LSX
> >> /* Enable LSX and restore context */
> >> int kvm_own_lsx(struct kvm_vcpu *vcpu)
> >> {
> >> - preempt_disable();
> >> -
> >> /* Enable LSX for guest */
> >> kvm_check_fcsr(vcpu, vcpu->arch.fpu.fcsr);
> >> set_csr_euen(CSR_EUEN_LSXEN | CSR_EUEN_FPEN);
> >> @@ -1381,8 +1396,6 @@ int kvm_own_lsx(struct kvm_vcpu *vcpu)
> >>
> >> trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_LSX);
> >> vcpu->arch.aux_inuse |= KVM_LARCH_LSX | KVM_LARCH_FPU;
> >> - preempt_enable();
> >> -
> >> return 0;
> >> }
> >> #endif
> >> @@ -1391,8 +1404,6 @@ int kvm_own_lsx(struct kvm_vcpu *vcpu)
> >> /* Enable LASX and restore context */
> >> int kvm_own_lasx(struct kvm_vcpu *vcpu)
> >> {
> >> - preempt_disable();
> >> -
> >> kvm_check_fcsr(vcpu, vcpu->arch.fpu.fcsr);
> >> set_csr_euen(CSR_EUEN_FPEN | CSR_EUEN_LSXEN | CSR_EUEN_LASXEN);
> >> switch (vcpu->arch.aux_inuse & (KVM_LARCH_FPU | KVM_LARCH_LSX)) {
> >> @@ -1414,8 +1425,6 @@ int kvm_own_lasx(struct kvm_vcpu *vcpu)
> >>
> >> trace_kvm_aux(vcpu, KVM_TRACE_AUX_RESTORE, KVM_TRACE_AUX_LASX);
> >> vcpu->arch.aux_inuse |= KVM_LARCH_LASX | KVM_LARCH_LSX | KVM_LARCH_FPU;
> >> - preempt_enable();
> >> -
> >> return 0;
> >> }
> >> #endif
> >> --
> >> 2.39.3
> >>
> >>
>
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