* [PATCH 1/4] KVM: Plumb in a @sched_in flag to kvm_arch_vcpu_load()
2024-04-30 19:31 [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load() Sean Christopherson
@ 2024-04-30 19:31 ` Sean Christopherson
2024-04-30 19:31 ` [PATCH 2/4] KVM: VMX: Move PLE grow/shrink helpers above vmx_vcpu_load() Sean Christopherson
` (3 subsequent siblings)
4 siblings, 0 replies; 8+ messages in thread
From: Sean Christopherson @ 2024-04-30 19:31 UTC (permalink / raw)
To: Marc Zyngier, Oliver Upton, Tianrui Zhao, Bibo Mao, Huacai Chen,
Michael Ellerman, Anup Patel, Paul Walmsley, Palmer Dabbelt,
Albert Ou, Christian Borntraeger, Janosch Frank, Claudio Imbrenda,
Sean Christopherson, Paolo Bonzini
Cc: kvm-riscv, kvm, linux-mips, linux-kernel, loongarch, kvmarm,
linux-riscv, linuxppc-dev, linux-arm-kernel
Add a @sched_in flag to kvm_arch_vcpu_load() to note that the vCPU is
being (re)loaded by kvm_sched_in(), i.e. after the vCPU was previously
scheduled out. KVM x86 currently uses a dedicated kvm_arch_sched_in()
hook, but that's unnecessarily brittle as the behavior of the arch hook
heavily depends on the arbitrary order of the two arch calls.
A separate hook also makes it unnecessarily difficult to do something
unique when re-loading vCPU during kvm_sched_in(), e.g. to optimize vCPU
loading if KVM knows that some CPU state couldn't have changed while the
vCPU was scheduled out.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/arm64/kvm/arm.c | 2 +-
arch/arm64/kvm/emulate-nested.c | 4 ++--
arch/arm64/kvm/reset.c | 2 +-
arch/loongarch/kvm/vcpu.c | 2 +-
arch/mips/kvm/mmu.c | 2 +-
arch/powerpc/kvm/powerpc.c | 2 +-
arch/riscv/kvm/vcpu.c | 4 ++--
arch/s390/kvm/kvm-s390.c | 2 +-
arch/x86/kvm/x86.c | 2 +-
include/linux/kvm_host.h | 2 +-
virt/kvm/kvm_main.c | 4 ++--
11 files changed, 14 insertions(+), 14 deletions(-)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index c4a0a35e02c7..30ea103bfacb 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -428,7 +428,7 @@ void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu)
}
-void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in)
{
struct kvm_s2_mmu *mmu;
int *last_ran;
diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
index 4697ba41b3a9..ad5458c47e5e 100644
--- a/arch/arm64/kvm/emulate-nested.c
+++ b/arch/arm64/kvm/emulate-nested.c
@@ -2193,7 +2193,7 @@ void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu)
*vcpu_pc(vcpu) = elr;
*vcpu_cpsr(vcpu) = spsr;
- kvm_arch_vcpu_load(vcpu, smp_processor_id());
+ kvm_arch_vcpu_load(vcpu, smp_processor_id(), false);
preempt_enable();
}
@@ -2274,7 +2274,7 @@ static int kvm_inject_nested(struct kvm_vcpu *vcpu, u64 esr_el2,
*/
__kvm_adjust_pc(vcpu);
- kvm_arch_vcpu_load(vcpu, smp_processor_id());
+ kvm_arch_vcpu_load(vcpu, smp_processor_id(), false);
preempt_enable();
return 1;
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 68d1d05672bd..654cf09c81e9 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -262,7 +262,7 @@ void kvm_reset_vcpu(struct kvm_vcpu *vcpu)
kvm_timer_vcpu_reset(vcpu);
if (loaded)
- kvm_arch_vcpu_load(vcpu, smp_processor_id());
+ kvm_arch_vcpu_load(vcpu, smp_processor_id(), false);
preempt_enable();
}
diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index 3a8779065f73..61d549c4f8d1 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -1050,7 +1050,7 @@ static int _kvm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
return 0;
}
-void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in)
{
unsigned long flags;
diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c
index c17157e700c0..6797799f3f32 100644
--- a/arch/mips/kvm/mmu.c
+++ b/arch/mips/kvm/mmu.c
@@ -682,7 +682,7 @@ static void kvm_mips_migrate_count(struct kvm_vcpu *vcpu)
}
/* Restore ASID once we are scheduled back after preemption */
-void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in)
{
unsigned long flags;
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index d32abe7fe6ab..8de620716875 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -826,7 +826,7 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
return kvmppc_core_pending_dec(vcpu);
}
-void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in)
{
#ifdef CONFIG_BOOKE
/*
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index b5ca9f2e98ac..a7b7f172fa61 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -87,7 +87,7 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
/* Reset the guest CSRs for hotplug usecase */
if (loaded)
- kvm_arch_vcpu_load(vcpu, smp_processor_id());
+ kvm_arch_vcpu_load(vcpu, smp_processor_id(), false);
put_cpu();
}
@@ -507,7 +507,7 @@ static void kvm_riscv_vcpu_setup_config(struct kvm_vcpu *vcpu)
}
}
-void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in)
{
struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
struct kvm_vcpu_config *cfg = &vcpu->arch.cfg;
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 5147b943a864..9f04dc312641 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -3713,7 +3713,7 @@ __u64 kvm_s390_get_cpu_timer(struct kvm_vcpu *vcpu)
return value;
}
-void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool shed_in)
{
gmap_enable(vcpu->arch.enabled_gmap);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2d2619d3eee4..925cadb18b55 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5003,7 +5003,7 @@ static bool need_emulate_wbinvd(struct kvm_vcpu *vcpu)
return kvm_arch_has_noncoherent_dma(vcpu->kvm);
}
-void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in)
{
/* Address WBINVD may be executed by guest */
if (need_emulate_wbinvd(vcpu)) {
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index afbc99264ffa..2f5e35eb7eab 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1498,7 +1498,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu);
void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu);
-void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
+void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in);
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu);
int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id);
int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 658581d4ad68..4a4b29a9bace 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -211,7 +211,7 @@ void vcpu_load(struct kvm_vcpu *vcpu)
__this_cpu_write(kvm_running_vcpu, vcpu);
preempt_notifier_register(&vcpu->preempt_notifier);
- kvm_arch_vcpu_load(vcpu, cpu);
+ kvm_arch_vcpu_load(vcpu, cpu, false);
put_cpu();
}
EXPORT_SYMBOL_GPL(vcpu_load);
@@ -6279,7 +6279,7 @@ static void kvm_sched_in(struct preempt_notifier *pn, int cpu)
__this_cpu_write(kvm_running_vcpu, vcpu);
kvm_arch_sched_in(vcpu, cpu);
- kvm_arch_vcpu_load(vcpu, cpu);
+ kvm_arch_vcpu_load(vcpu, cpu, true);
}
static void kvm_sched_out(struct preempt_notifier *pn,
--
2.45.0.rc0.197.gbae5840b3b-goog
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH 2/4] KVM: VMX: Move PLE grow/shrink helpers above vmx_vcpu_load()
2024-04-30 19:31 [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load() Sean Christopherson
2024-04-30 19:31 ` [PATCH 1/4] KVM: Plumb in a @sched_in flag to kvm_arch_vcpu_load() Sean Christopherson
@ 2024-04-30 19:31 ` Sean Christopherson
2024-04-30 19:31 ` [PATCH 3/4] KVM: x86: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load() Sean Christopherson
` (2 subsequent siblings)
4 siblings, 0 replies; 8+ messages in thread
From: Sean Christopherson @ 2024-04-30 19:31 UTC (permalink / raw)
To: Marc Zyngier, Oliver Upton, Tianrui Zhao, Bibo Mao, Huacai Chen,
Michael Ellerman, Anup Patel, Paul Walmsley, Palmer Dabbelt,
Albert Ou, Christian Borntraeger, Janosch Frank, Claudio Imbrenda,
Sean Christopherson, Paolo Bonzini
Cc: kvm-riscv, kvm, linux-mips, linux-kernel, loongarch, kvmarm,
linux-riscv, linuxppc-dev, linux-arm-kernel
Move VMX's {grow,shrink}_ple_window() above vmx_vcpu_load() in preparation
of moving the sched_in logic, which handles shrinking the PLE window, into
vmx_vcpu_load().
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/vmx.c | 64 +++++++++++++++++++++---------------------
1 file changed, 32 insertions(+), 32 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 6780313914f8..cb36db7b6140 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1402,6 +1402,38 @@ static void vmx_write_guest_kernel_gs_base(struct vcpu_vmx *vmx, u64 data)
}
#endif
+static void grow_ple_window(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+ unsigned int old = vmx->ple_window;
+
+ vmx->ple_window = __grow_ple_window(old, ple_window,
+ ple_window_grow,
+ ple_window_max);
+
+ if (vmx->ple_window != old) {
+ vmx->ple_window_dirty = true;
+ trace_kvm_ple_window_update(vcpu->vcpu_id,
+ vmx->ple_window, old);
+ }
+}
+
+static void shrink_ple_window(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+ unsigned int old = vmx->ple_window;
+
+ vmx->ple_window = __shrink_ple_window(old, ple_window,
+ ple_window_shrink,
+ ple_window);
+
+ if (vmx->ple_window != old) {
+ vmx->ple_window_dirty = true;
+ trace_kvm_ple_window_update(vcpu->vcpu_id,
+ vmx->ple_window, old);
+ }
+}
+
void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu,
struct loaded_vmcs *buddy)
{
@@ -5871,38 +5903,6 @@ int vmx_vcpu_pre_run(struct kvm_vcpu *vcpu)
return 1;
}
-static void grow_ple_window(struct kvm_vcpu *vcpu)
-{
- struct vcpu_vmx *vmx = to_vmx(vcpu);
- unsigned int old = vmx->ple_window;
-
- vmx->ple_window = __grow_ple_window(old, ple_window,
- ple_window_grow,
- ple_window_max);
-
- if (vmx->ple_window != old) {
- vmx->ple_window_dirty = true;
- trace_kvm_ple_window_update(vcpu->vcpu_id,
- vmx->ple_window, old);
- }
-}
-
-static void shrink_ple_window(struct kvm_vcpu *vcpu)
-{
- struct vcpu_vmx *vmx = to_vmx(vcpu);
- unsigned int old = vmx->ple_window;
-
- vmx->ple_window = __shrink_ple_window(old, ple_window,
- ple_window_shrink,
- ple_window);
-
- if (vmx->ple_window != old) {
- vmx->ple_window_dirty = true;
- trace_kvm_ple_window_update(vcpu->vcpu_id,
- vmx->ple_window, old);
- }
-}
-
/*
* Indicate a busy-waiting vcpu in spinlock. We do not enable the PAUSE
* exiting, so only get here on cpu with PAUSE-Loop-Exiting.
--
2.45.0.rc0.197.gbae5840b3b-goog
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH 3/4] KVM: x86: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load()
2024-04-30 19:31 [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load() Sean Christopherson
2024-04-30 19:31 ` [PATCH 1/4] KVM: Plumb in a @sched_in flag to kvm_arch_vcpu_load() Sean Christopherson
2024-04-30 19:31 ` [PATCH 2/4] KVM: VMX: Move PLE grow/shrink helpers above vmx_vcpu_load() Sean Christopherson
@ 2024-04-30 19:31 ` Sean Christopherson
2024-04-30 19:31 ` [PATCH 4/4] KVM: Delete the now unused kvm_arch_sched_in() Sean Christopherson
2024-05-01 0:28 ` [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load() Oliver Upton
4 siblings, 0 replies; 8+ messages in thread
From: Sean Christopherson @ 2024-04-30 19:31 UTC (permalink / raw)
To: Marc Zyngier, Oliver Upton, Tianrui Zhao, Bibo Mao, Huacai Chen,
Michael Ellerman, Anup Patel, Paul Walmsley, Palmer Dabbelt,
Albert Ou, Christian Borntraeger, Janosch Frank, Claudio Imbrenda,
Sean Christopherson, Paolo Bonzini
Cc: kvm-riscv, kvm, linux-mips, linux-kernel, loongarch, kvmarm,
linux-riscv, linuxppc-dev, linux-arm-kernel
Fold the guts of kvm_arch_sched_in() into kvm_arch_vcpu_load(), keying
off the recently added @sched_in as appropriate.
Note, there is a very slight functional change, as PLE shrink updates will
now happen after blasting WBINVD, but that is quite uninteresting.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/include/asm/kvm-x86-ops.h | 1 -
arch/x86/include/asm/kvm_host.h | 4 +---
arch/x86/kvm/svm/svm.c | 13 ++++---------
arch/x86/kvm/vmx/main.c | 2 --
arch/x86/kvm/vmx/vmx.c | 11 ++++-------
arch/x86/kvm/vmx/x86_ops.h | 3 +--
arch/x86/kvm/x86.c | 19 +++++++++++--------
7 files changed, 21 insertions(+), 32 deletions(-)
diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 5187fcf4b610..910d06cdb86b 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -103,7 +103,6 @@ KVM_X86_OP(write_tsc_multiplier)
KVM_X86_OP(get_exit_info)
KVM_X86_OP(check_intercept)
KVM_X86_OP(handle_exit_irqoff)
-KVM_X86_OP(sched_in)
KVM_X86_OP_OPTIONAL(update_cpu_dirty_logging)
KVM_X86_OP_OPTIONAL(vcpu_blocking)
KVM_X86_OP_OPTIONAL(vcpu_unblocking)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 01c69840647e..9fd1ec82303d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1624,7 +1624,7 @@ struct kvm_x86_ops {
void (*vcpu_reset)(struct kvm_vcpu *vcpu, bool init_event);
void (*prepare_switch_to_guest)(struct kvm_vcpu *vcpu);
- void (*vcpu_load)(struct kvm_vcpu *vcpu, int cpu);
+ void (*vcpu_load)(struct kvm_vcpu *vcpu, int cpu, bool sched_in);
void (*vcpu_put)(struct kvm_vcpu *vcpu);
void (*update_exception_bitmap)(struct kvm_vcpu *vcpu);
@@ -1746,8 +1746,6 @@ struct kvm_x86_ops {
struct x86_exception *exception);
void (*handle_exit_irqoff)(struct kvm_vcpu *vcpu);
- void (*sched_in)(struct kvm_vcpu *vcpu, int cpu);
-
/*
* Size of the CPU's dirty log buffer, i.e. VMX's PML buffer. A zero
* value indicates CPU dirty logging is unsupported or disabled.
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 0f3b59da0d4a..6d9763dc4fed 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1539,11 +1539,14 @@ static void svm_prepare_host_switch(struct kvm_vcpu *vcpu)
to_svm(vcpu)->guest_state_loaded = false;
}
-static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in)
{
struct vcpu_svm *svm = to_svm(vcpu);
struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, cpu);
+ if (sched_in && !kvm_pause_in_guest(vcpu->kvm))
+ shrink_ple_window(vcpu);
+
if (sd->current_vmcb != svm->vmcb) {
sd->current_vmcb = svm->vmcb;
@@ -4548,12 +4551,6 @@ static void svm_handle_exit_irqoff(struct kvm_vcpu *vcpu)
vcpu->arch.at_instruction_boundary = true;
}
-static void svm_sched_in(struct kvm_vcpu *vcpu, int cpu)
-{
- if (!kvm_pause_in_guest(vcpu->kvm))
- shrink_ple_window(vcpu);
-}
-
static void svm_setup_mce(struct kvm_vcpu *vcpu)
{
/* [63:9] are reserved. */
@@ -5013,8 +5010,6 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
.check_intercept = svm_check_intercept,
.handle_exit_irqoff = svm_handle_exit_irqoff,
- .sched_in = svm_sched_in,
-
.nested_ops = &svm_nested_ops,
.deliver_interrupt = svm_deliver_interrupt,
diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
index 7c546ad3e4c9..4fee9a8cc5a1 100644
--- a/arch/x86/kvm/vmx/main.c
+++ b/arch/x86/kvm/vmx/main.c
@@ -121,8 +121,6 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
.check_intercept = vmx_check_intercept,
.handle_exit_irqoff = vmx_handle_exit_irqoff,
- .sched_in = vmx_sched_in,
-
.cpu_dirty_log_size = PML_ENTITY_NUM,
.update_cpu_dirty_logging = vmx_update_cpu_dirty_logging,
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index cb36db7b6140..ccea594187c7 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1505,10 +1505,13 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu,
* Switches to specified vcpu, until a matching vcpu_put(), but assumes
* vcpu mutex is already taken.
*/
-void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
+ if (sched_in && !kvm_pause_in_guest(vcpu->kvm))
+ shrink_ple_window(vcpu);
+
vmx_vcpu_load_vmcs(vcpu, cpu, NULL);
vmx_vcpu_pi_load(vcpu, cpu);
@@ -8093,12 +8096,6 @@ void vmx_cancel_hv_timer(struct kvm_vcpu *vcpu)
}
#endif
-void vmx_sched_in(struct kvm_vcpu *vcpu, int cpu)
-{
- if (!kvm_pause_in_guest(vcpu->kvm))
- shrink_ple_window(vcpu);
-}
-
void vmx_update_cpu_dirty_logging(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
index 502704596c83..b7104a5f623e 100644
--- a/arch/x86/kvm/vmx/x86_ops.h
+++ b/arch/x86/kvm/vmx/x86_ops.h
@@ -23,7 +23,7 @@ int vmx_vcpu_pre_run(struct kvm_vcpu *vcpu);
fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit);
void vmx_vcpu_free(struct kvm_vcpu *vcpu);
void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event);
-void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
+void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in);
void vmx_vcpu_put(struct kvm_vcpu *vcpu);
int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath);
void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu);
@@ -112,7 +112,6 @@ u64 vmx_get_l2_tsc_multiplier(struct kvm_vcpu *vcpu);
void vmx_write_tsc_offset(struct kvm_vcpu *vcpu);
void vmx_write_tsc_multiplier(struct kvm_vcpu *vcpu);
void vmx_request_immediate_exit(struct kvm_vcpu *vcpu);
-void vmx_sched_in(struct kvm_vcpu *vcpu, int cpu);
void vmx_update_cpu_dirty_logging(struct kvm_vcpu *vcpu);
#ifdef CONFIG_X86_64
int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 925cadb18b55..9b0a21f2e56e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5005,6 +5005,16 @@ static bool need_emulate_wbinvd(struct kvm_vcpu *vcpu)
void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in)
{
+ struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
+
+ if (sched_in) {
+ vcpu->arch.l1tf_flush_l1d = true;
+ if (pmu->version && unlikely(pmu->event_count)) {
+ pmu->need_cleanup = true;
+ kvm_make_request(KVM_REQ_PMU, vcpu);
+ }
+ }
+
/* Address WBINVD may be executed by guest */
if (need_emulate_wbinvd(vcpu)) {
if (static_call(kvm_x86_has_wbinvd_exit)())
@@ -5014,7 +5024,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in)
wbinvd_ipi, NULL, 1);
}
- static_call(kvm_x86_vcpu_load)(vcpu, cpu);
+ static_call(kvm_x86_vcpu_load)(vcpu, cpu, sched_in);
/* Save host pkru register if supported */
vcpu->arch.host_pkru = read_pkru();
@@ -12569,14 +12579,7 @@ bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu)
void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu)
{
- struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
- vcpu->arch.l1tf_flush_l1d = true;
- if (pmu->version && unlikely(pmu->event_count)) {
- pmu->need_cleanup = true;
- kvm_make_request(KVM_REQ_PMU, vcpu);
- }
- static_call(kvm_x86_sched_in)(vcpu, cpu);
}
void kvm_arch_free_vm(struct kvm *kvm)
--
2.45.0.rc0.197.gbae5840b3b-goog
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH 4/4] KVM: Delete the now unused kvm_arch_sched_in()
2024-04-30 19:31 [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load() Sean Christopherson
` (2 preceding siblings ...)
2024-04-30 19:31 ` [PATCH 3/4] KVM: x86: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load() Sean Christopherson
@ 2024-04-30 19:31 ` Sean Christopherson
2024-05-01 0:28 ` [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load() Oliver Upton
4 siblings, 0 replies; 8+ messages in thread
From: Sean Christopherson @ 2024-04-30 19:31 UTC (permalink / raw)
To: Marc Zyngier, Oliver Upton, Tianrui Zhao, Bibo Mao, Huacai Chen,
Michael Ellerman, Anup Patel, Paul Walmsley, Palmer Dabbelt,
Albert Ou, Christian Borntraeger, Janosch Frank, Claudio Imbrenda,
Sean Christopherson, Paolo Bonzini
Cc: kvm-riscv, kvm, linux-mips, linux-kernel, loongarch, kvmarm,
linux-riscv, linuxppc-dev, linux-arm-kernel
Delete kvm_arch_sched_in() now that all implementations are nops.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/arm64/include/asm/kvm_host.h | 1 -
arch/loongarch/include/asm/kvm_host.h | 1 -
arch/mips/include/asm/kvm_host.h | 1 -
arch/powerpc/include/asm/kvm_host.h | 1 -
arch/riscv/include/asm/kvm_host.h | 1 -
arch/s390/include/asm/kvm_host.h | 1 -
arch/x86/kvm/pmu.c | 6 +++---
arch/x86/kvm/x86.c | 5 -----
include/linux/kvm_host.h | 2 --
virt/kvm/kvm_main.c | 1 -
10 files changed, 3 insertions(+), 17 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 9e8a496fb284..a12d3bb0b590 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1180,7 +1180,6 @@ static inline bool kvm_system_needs_idmapped_vectors(void)
}
static inline void kvm_arch_sync_events(struct kvm *kvm) {}
-static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
void kvm_arm_init_debug(void);
void kvm_arm_vcpu_init_debug(struct kvm_vcpu *vcpu);
diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
index 69305441f40d..64ca60a3ce24 100644
--- a/arch/loongarch/include/asm/kvm_host.h
+++ b/arch/loongarch/include/asm/kvm_host.h
@@ -228,7 +228,6 @@ static inline bool kvm_is_ifetch_fault(struct kvm_vcpu_arch *arch)
static inline void kvm_arch_hardware_unsetup(void) {}
static inline void kvm_arch_sync_events(struct kvm *kvm) {}
static inline void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen) {}
-static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu) {}
static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {}
static inline void kvm_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}
diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index 179f320cc231..6743a57c1ab4 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -890,7 +890,6 @@ static inline void kvm_arch_sync_events(struct kvm *kvm) {}
static inline void kvm_arch_free_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot) {}
static inline void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen) {}
-static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu) {}
static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {}
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 8abac532146e..c4fb6a27fb92 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -897,7 +897,6 @@ struct kvm_vcpu_arch {
static inline void kvm_arch_sync_events(struct kvm *kvm) {}
static inline void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen) {}
static inline void kvm_arch_flush_shadow_all(struct kvm *kvm) {}
-static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu) {}
static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {}
diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 484d04a92fa6..6cd7a576ef14 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -272,7 +272,6 @@ struct kvm_vcpu_arch {
};
static inline void kvm_arch_sync_events(struct kvm *kvm) {}
-static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
#define KVM_RISCV_GSTAGE_TLB_MIN_ORDER 12
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 95990461888f..e9fcaf4607a6 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -1045,7 +1045,6 @@ extern int kvm_s390_gisc_register(struct kvm *kvm, u32 gisc);
extern int kvm_s390_gisc_unregister(struct kvm *kvm, u32 gisc);
static inline void kvm_arch_sync_events(struct kvm *kvm) {}
-static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
static inline void kvm_arch_free_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot) {}
static inline void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen) {}
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index c397b28e3d1b..75346a588e13 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -521,9 +521,9 @@ void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
}
/*
- * Unused perf_events are only released if the corresponding MSRs
- * weren't accessed during the last vCPU time slice. kvm_arch_sched_in
- * triggers KVM_REQ_PMU if cleanup is needed.
+ * Release unused perf_events if the corresponding guest MSRs weren't
+ * accessed during the last vCPU time slice (need_cleanup is set when
+ * the vCPU is scheduled back in).
*/
if (unlikely(pmu->need_cleanup))
kvm_pmu_cleanup(vcpu);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9b0a21f2e56e..17d6ce0d4fa6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12577,11 +12577,6 @@ bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu)
return (vcpu->arch.apic_base & MSR_IA32_APICBASE_BSP) != 0;
}
-void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu)
-{
-
-}
-
void kvm_arch_free_vm(struct kvm *kvm)
{
#if IS_ENABLED(CONFIG_HYPERV)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 2f5e35eb7eab..85b6dd7927fe 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1496,8 +1496,6 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
struct kvm_guest_debug *dbg);
int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu);
-void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu);
-
void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool sched_in);
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu);
int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4a4b29a9bace..b154b22a3b84 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -6278,7 +6278,6 @@ static void kvm_sched_in(struct preempt_notifier *pn, int cpu)
WRITE_ONCE(vcpu->ready, false);
__this_cpu_write(kvm_running_vcpu, vcpu);
- kvm_arch_sched_in(vcpu, cpu);
kvm_arch_vcpu_load(vcpu, cpu, true);
}
--
2.45.0.rc0.197.gbae5840b3b-goog
^ permalink raw reply related [flat|nested] 8+ messages in thread* Re: [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load()
2024-04-30 19:31 [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load() Sean Christopherson
` (3 preceding siblings ...)
2024-04-30 19:31 ` [PATCH 4/4] KVM: Delete the now unused kvm_arch_sched_in() Sean Christopherson
@ 2024-05-01 0:28 ` Oliver Upton
2024-05-01 14:28 ` Sean Christopherson
4 siblings, 1 reply; 8+ messages in thread
From: Oliver Upton @ 2024-05-01 0:28 UTC (permalink / raw)
To: Sean Christopherson
Cc: kvm, linux-kernel, linux-riscv, Claudio Imbrenda, Janosch Frank,
Marc Zyngier, Huacai Chen, Christian Borntraeger, Albert Ou,
Bibo Mao, loongarch, Paul Walmsley, kvmarm, linux-arm-kernel,
Anup Patel, linux-mips, Palmer Dabbelt, kvm-riscv, Paolo Bonzini,
Tianrui Zhao, linuxppc-dev
On Tue, Apr 30, 2024 at 12:31:53PM -0700, Sean Christopherson wrote:
> Drop kvm_arch_sched_in() and instead pass a @sched_in boolean to
> kvm_arch_vcpu_load().
>
> While fiddling with an idea for optimizing state management on AMD CPUs,
> I wanted to skip re-saving certain host state when a vCPU is scheduled back
> in, as the state (theoretically) shouldn't change for the task while it's
> scheduled out. Actually doing that was annoying and unnecessarily brittle
> due to having a separate API for the kvm_sched_in() case (the state save
> needed to be in kvm_arch_vcpu_load() for the common path).
>
> E.g. I could have set a "temporary"-ish flag somewhere in kvm_vcpu, but (a)
> that's gross and (b) it would rely on the arbitrary ordering between
> sched_in() and vcpu_load() staying the same.
Another option would be to change the rules around kvm_arch_sched_in()
where the callee is expected to load the vCPU context.
The default implementation could just call kvm_arch_vcpu_load() directly
and the x86 implementation can order things the way it wants before
kvm_arch_vcpu_load().
I say this because ...
> The only real downside I see is that arm64 and riscv end up having to pass
> "false" for their direct usage of kvm_arch_vcpu_load(), and passing boolean
> literals isn't ideal. But that can be solved by adding an inner helper that
> omits the @sched_in param (I almost added a patch to do that, but I couldn't
> convince myself it was necessary).
Needing to pass @sched_in for other usage of kvm_arch_vcpu_load() hurts
readability, especially when no other architecture besides x86 cares
about it.
--
Thanks,
Oliver
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load()
2024-05-01 0:28 ` [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load() Oliver Upton
@ 2024-05-01 14:28 ` Sean Christopherson
2024-05-01 18:01 ` Oliver Upton
0 siblings, 1 reply; 8+ messages in thread
From: Sean Christopherson @ 2024-05-01 14:28 UTC (permalink / raw)
To: Oliver Upton
Cc: kvm, linux-kernel, linux-riscv, Claudio Imbrenda, Janosch Frank,
Marc Zyngier, Huacai Chen, Christian Borntraeger, Albert Ou,
Bibo Mao, loongarch, Paul Walmsley, kvmarm, linux-arm-kernel,
Anup Patel, linux-mips, Palmer Dabbelt, kvm-riscv, Paolo Bonzini,
Tianrui Zhao, linuxppc-dev
On Wed, May 01, 2024, Oliver Upton wrote:
> On Tue, Apr 30, 2024 at 12:31:53PM -0700, Sean Christopherson wrote:
> > Drop kvm_arch_sched_in() and instead pass a @sched_in boolean to
> > kvm_arch_vcpu_load().
> >
> > While fiddling with an idea for optimizing state management on AMD CPUs,
> > I wanted to skip re-saving certain host state when a vCPU is scheduled back
> > in, as the state (theoretically) shouldn't change for the task while it's
> > scheduled out. Actually doing that was annoying and unnecessarily brittle
> > due to having a separate API for the kvm_sched_in() case (the state save
> > needed to be in kvm_arch_vcpu_load() for the common path).
> >
> > E.g. I could have set a "temporary"-ish flag somewhere in kvm_vcpu, but (a)
> > that's gross and (b) it would rely on the arbitrary ordering between
> > sched_in() and vcpu_load() staying the same.
>
> Another option would be to change the rules around kvm_arch_sched_in()
> where the callee is expected to load the vCPU context.
>
> The default implementation could just call kvm_arch_vcpu_load() directly
> and the x86 implementation can order things the way it wants before
> kvm_arch_vcpu_load().
>
> I say this because ...
>
> > The only real downside I see is that arm64 and riscv end up having to pass
> > "false" for their direct usage of kvm_arch_vcpu_load(), and passing boolean
> > literals isn't ideal. But that can be solved by adding an inner helper that
> > omits the @sched_in param (I almost added a patch to do that, but I couldn't
> > convince myself it was necessary).
>
> Needing to pass @sched_in for other usage of kvm_arch_vcpu_load() hurts
> readability, especially when no other architecture besides x86 cares
> about it.
Yeah, that bothers me too.
I tried your suggestion of having x86's kvm_arch_sched_in() do kvm_arch_vcpu_load(),
and even with an added kvm_arch_sched_out() to provide symmetry, the x86 code is
kludgy, and even the common code is a bit confusing as it's not super obvious
that kvm_sched_{in,out}() is really just kvm_arch_vcpu_{load,put}().
Staring a bit more at the vCPU flags we have, adding a "bool scheduled_out" isn't
terribly gross if it's done in common code and persists across load() and put(),
i.e. isn't so blatantly a temporary field. And because it's easy, it could be
set with WRITE_ONCE() so that if it can be read cross-task if there's ever a
reason to do so.
The x86 code ends up being less ugly, and adding future arch/vendor code for
sched_in() *or* sched_out() requires minimal churn, e.g. arch code doesn't need
to override kvm_arch_sched_in().
The only weird part is that vcpu->preempted and vcpu->ready have slightly
different behavior, as they are cleared before kvm_arch_vcpu_load(). But the
weirdness is really with those flags no having symmetry, not with scheduled_out
itself.
Thoughts?
static void kvm_sched_in(struct preempt_notifier *pn, int cpu)
{
struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);
WRITE_ONCE(vcpu->preempted, false);
WRITE_ONCE(vcpu->ready, false);
__this_cpu_write(kvm_running_vcpu, vcpu);
kvm_arch_vcpu_load(vcpu, cpu);
WRITE_ONCE(vcpu->scheduled_out, false);
}
static void kvm_sched_out(struct preempt_notifier *pn,
struct task_struct *next)
{
struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);
WRITE_ONCE(vcpu->scheduled_out, true);
if (current->on_rq) {
WRITE_ONCE(vcpu->preempted, true);
WRITE_ONCE(vcpu->ready, true);
}
kvm_arch_vcpu_put(vcpu);
__this_cpu_write(kvm_running_vcpu, NULL);
}
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH 0/4] KVM: Fold kvm_arch_sched_in() into kvm_arch_vcpu_load()
2024-05-01 14:28 ` Sean Christopherson
@ 2024-05-01 18:01 ` Oliver Upton
0 siblings, 0 replies; 8+ messages in thread
From: Oliver Upton @ 2024-05-01 18:01 UTC (permalink / raw)
To: Sean Christopherson
Cc: kvm, linux-kernel, linux-riscv, Claudio Imbrenda, Janosch Frank,
Marc Zyngier, Huacai Chen, Christian Borntraeger, Albert Ou,
Bibo Mao, loongarch, Paul Walmsley, kvmarm, linux-arm-kernel,
Anup Patel, linux-mips, Palmer Dabbelt, kvm-riscv, Paolo Bonzini,
Tianrui Zhao, linuxppc-dev
On Wed, May 01, 2024 at 07:28:21AM -0700, Sean Christopherson wrote:
> On Wed, May 01, 2024, Oliver Upton wrote:
> > On Tue, Apr 30, 2024 at 12:31:53PM -0700, Sean Christopherson wrote:
> > > Drop kvm_arch_sched_in() and instead pass a @sched_in boolean to
> > > kvm_arch_vcpu_load().
> > >
> > > While fiddling with an idea for optimizing state management on AMD CPUs,
> > > I wanted to skip re-saving certain host state when a vCPU is scheduled back
> > > in, as the state (theoretically) shouldn't change for the task while it's
> > > scheduled out. Actually doing that was annoying and unnecessarily brittle
> > > due to having a separate API for the kvm_sched_in() case (the state save
> > > needed to be in kvm_arch_vcpu_load() for the common path).
> > >
> > > E.g. I could have set a "temporary"-ish flag somewhere in kvm_vcpu, but (a)
> > > that's gross and (b) it would rely on the arbitrary ordering between
> > > sched_in() and vcpu_load() staying the same.
> >
> > Another option would be to change the rules around kvm_arch_sched_in()
> > where the callee is expected to load the vCPU context.
> >
> > The default implementation could just call kvm_arch_vcpu_load() directly
> > and the x86 implementation can order things the way it wants before
> > kvm_arch_vcpu_load().
> >
> > I say this because ...
> >
> > > The only real downside I see is that arm64 and riscv end up having to pass
> > > "false" for their direct usage of kvm_arch_vcpu_load(), and passing boolean
> > > literals isn't ideal. But that can be solved by adding an inner helper that
> > > omits the @sched_in param (I almost added a patch to do that, but I couldn't
> > > convince myself it was necessary).
> >
> > Needing to pass @sched_in for other usage of kvm_arch_vcpu_load() hurts
> > readability, especially when no other architecture besides x86 cares
> > about it.
>
> Yeah, that bothers me too.
>
> I tried your suggestion of having x86's kvm_arch_sched_in() do kvm_arch_vcpu_load(),
> and even with an added kvm_arch_sched_out() to provide symmetry, the x86 code is
> kludgy, and even the common code is a bit confusing as it's not super obvious
> that kvm_sched_{in,out}() is really just kvm_arch_vcpu_{load,put}().
>
> Staring a bit more at the vCPU flags we have, adding a "bool scheduled_out" isn't
> terribly gross if it's done in common code and persists across load() and put(),
> i.e. isn't so blatantly a temporary field. And because it's easy, it could be
> set with WRITE_ONCE() so that if it can be read cross-task if there's ever a
> reason to do so.
>
> The x86 code ends up being less ugly, and adding future arch/vendor code for
> sched_in() *or* sched_out() requires minimal churn, e.g. arch code doesn't need
> to override kvm_arch_sched_in().
>
> The only weird part is that vcpu->preempted and vcpu->ready have slightly
> different behavior, as they are cleared before kvm_arch_vcpu_load(). But the
> weirdness is really with those flags no having symmetry, not with scheduled_out
> itself.
>
> Thoughts?
Yeah, this seems reasonable. Perhaps scheduled_out could be a nice hint
for guardrails / sanity checks in the future.
--
Thanks,
Oliver
^ permalink raw reply [flat|nested] 8+ messages in thread