[PATCH v2 0/5] KVM: arm64: Reorganise vcpu first run

[PATCH v2 0/5] KVM: arm64: Reorganise vcpu first run

[Marc Zyngier]

This is v2 of this series reworking the vcpu first run.

KVM/arm64 relies heavily on a bunch of things to be done on the first
run of the vcpu. We also do a bunch of things on PID change. It turns
out that these two things are pretty similar (the first PID change is
also the first run).

This small series aims at simplifying all that, and to get rid of the
vcpu->arch.has_run_once state. On top of being a decent cleanup, it
also results in a minor performance improvement (my Debian installer
on M1 consistently went from 2:23 down to 2:22, a ~0.6% reduction in
execution time).

* From v1 [1]:
  - Moved the kvm_vcpu_initialized() check into kvm_vcpu_first_run_init()
  - Reorganise the series so that the userspace irqchip static key
    change appears earlier
  - Collected Andrew's RBs

[1] https://lore.kernel/org/r/20211015090822.2994920-1-maz@kernel.org

Marc Zyngier (5):
  KVM: arm64: Move SVE state mapping at HYP to finalize-time
  KVM: arm64: Move kvm_arch_vcpu_run_pid_change() out of line
  KVM: arm64: Restructure the point where has_run_once is advertised
  KVM: arm64: Merge kvm_arch_vcpu_run_pid_change() and
    kvm_vcpu_first_run_init()
  KVM: arm64: Drop vcpu->arch.has_run_once for vcpu->pid

 arch/arm64/include/asm/kvm_host.h | 12 ++-----
 arch/arm64/kvm/arm.c              | 57 +++++++++++++++++--------------
 arch/arm64/kvm/fpsimd.c           | 11 ------
 arch/arm64/kvm/reset.c            | 11 +++++-
 arch/arm64/kvm/vgic/vgic-init.c   |  2 +-
 5 files changed, 46 insertions(+), 47 deletions(-)

-- 
2.30.2


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[PATCH v2 1/5] KVM: arm64: Move SVE state mapping at HYP to finalize-time

[Marc Zyngier]

We currently map the SVE state to HYP on detection of a PID change.
Although this matches what we do for FPSIMD, this is pretty pointless
for SVE, as the buffer is per-vcpu and has nothing to do with the
thread that is being run.

Move the mapping of the SVE state to finalize-time, which is where
we allocate the state memory, and thus the most logical place to
do this.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/fpsimd.c | 11 -----------
 arch/arm64/kvm/reset.c  | 11 ++++++++++-
 2 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 5621020b28de..62c0d78da7be 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -43,17 +43,6 @@ int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
 	if (ret)
 		goto error;
 
-	if (vcpu->arch.sve_state) {
-		void *sve_end;
-
-		sve_end = vcpu->arch.sve_state + vcpu_sve_state_size(vcpu);
-
-		ret = create_hyp_mappings(vcpu->arch.sve_state, sve_end,
-					  PAGE_HYP);
-		if (ret)
-			goto error;
-	}
-
 	vcpu->arch.host_thread_info = kern_hyp_va(ti);
 	vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
 error:
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 5ce36b0a3343..9e904a9244c1 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -94,6 +94,8 @@ static int kvm_vcpu_finalize_sve(struct kvm_vcpu *vcpu)
 {
 	void *buf;
 	unsigned int vl;
+	size_t reg_sz;
+	int ret;
 
 	vl = vcpu->arch.sve_max_vl;
 
@@ -106,10 +108,17 @@ static int kvm_vcpu_finalize_sve(struct kvm_vcpu *vcpu)
 		    vl > SVE_VL_ARCH_MAX))
 		return -EIO;
 
-	buf = kzalloc(SVE_SIG_REGS_SIZE(sve_vq_from_vl(vl)), GFP_KERNEL);
+	reg_sz = vcpu_sve_state_size(vcpu);
+	buf = kzalloc(reg_sz, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;
 
+	ret = create_hyp_mappings(buf, buf + reg_sz, PAGE_HYP);
+	if (ret) {
+		kfree(buf);
+		return ret;
+	}
+	
 	vcpu->arch.sve_state = buf;
 	vcpu->arch.flags |= KVM_ARM64_VCPU_SVE_FINALIZED;
 	return 0;
-- 
2.30.2


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[PATCH v2 2/5] KVM: arm64: Move kvm_arch_vcpu_run_pid_change() out of line

[Marc Zyngier]

Having kvm_arch_vcpu_run_pid_change() inline doesn't bring anything
to the table. Move it next to kvm_vcpu_first_run_init(), which will
be convenient for what is next to come.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_host.h | 7 +------
 arch/arm64/kvm/arm.c              | 5 +++++
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index f8be56d5342b..d7107d627c54 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -748,12 +748,7 @@ static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
 void kvm_arch_vcpu_load_debug_state_flags(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu);
 
-#ifdef CONFIG_KVM /* Avoid conflicts with core headers if CONFIG_KVM=n */
-static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
-{
-	return kvm_arch_vcpu_run_map_fp(vcpu);
-}
-
+#ifdef CONFIG_KVM
 void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr);
 void kvm_clr_pmu_events(u32 clr);
 
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index fe102cd2e518..ccb59ac54976 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -583,6 +583,11 @@ static void update_vmid(struct kvm_vmid *vmid)
 	spin_unlock(&kvm_vmid_lock);
 }
 
+int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
+{
+	return kvm_arch_vcpu_run_map_fp(vcpu);
+}
+
 static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
 {
 	struct kvm *kvm = vcpu->kvm;
-- 
2.30.2


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[PATCH v2 3/5] KVM: arm64: Restructure the point where has_run_once is advertised

[Marc Zyngier]

Restructure kvm_vcpu_first_run_init() to set the has_run_once
flag after having completed all the "run once" activities.

This includes moving the flip of the userspace irqchip static key
to a point where nothing can fail.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/arm.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index ccb59ac54976..42efca9853fb 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -599,8 +599,6 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
 	if (!kvm_arm_vcpu_is_finalized(vcpu))
 		return -EPERM;
 
-	vcpu->arch.has_run_once = true;
-
 	kvm_arm_vcpu_init_debug(vcpu);
 
 	if (likely(irqchip_in_kernel(kvm))) {
@@ -611,12 +609,6 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
 		ret = kvm_vgic_map_resources(kvm);
 		if (ret)
 			return ret;
-	} else {
-		/*
-		 * Tell the rest of the code that there are userspace irqchip
-		 * VMs in the wild.
-		 */
-		static_branch_inc(&userspace_irqchip_in_use);
 	}
 
 	ret = kvm_timer_enable(vcpu);
@@ -624,6 +616,18 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
 		return ret;
 
 	ret = kvm_arm_pmu_v3_enable(vcpu);
+	if (ret)
+		return ret;
+
+	if (!irqchip_in_kernel(kvm)) {
+		/*
+		 * Tell the rest of the code that there are userspace irqchip
+		 * VMs in the wild.
+		 */
+		static_branch_inc(&userspace_irqchip_in_use);
+	}
+
+	vcpu->arch.has_run_once = true;
 
 	return ret;
 }
-- 
2.30.2


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[PATCH v2 4/5] KVM: arm64: Merge kvm_arch_vcpu_run_pid_change() and kvm_vcpu_first_run_init()

[Marc Zyngier]

The kvm_arch_vcpu_run_pid_change() helper gets called on each PID
change. The kvm_vcpu_first_run_init() helper gets run on the...
first run(!) of a vcpu.

As it turns out, the first run of a vcpu also triggers a PID change
event (vcpu->pid is initially NULL).

Use this property to merge these two helpers and get rid of another
arm64-specific oddity.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/arm.c | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 42efca9853fb..a52f6a76485d 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -583,22 +583,34 @@ static void update_vmid(struct kvm_vmid *vmid)
 	spin_unlock(&kvm_vmid_lock);
 }
 
-int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
+static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu)
 {
-	return kvm_arch_vcpu_run_map_fp(vcpu);
+	return vcpu->arch.target >= 0;
 }
 
-static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
+/*
+ * Handle both the initialisation that is being done when the vcpu is
+ * run for the first time, as well as the updates that must be
+ * performed each time we get a new thread dealing with this vcpu.
+ */
+int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
 {
 	struct kvm *kvm = vcpu->kvm;
-	int ret = 0;
+	int ret;
 
-	if (likely(vcpu->arch.has_run_once))
-		return 0;
+	if (!kvm_vcpu_initialized(vcpu))
+		return -ENOEXEC;
 
 	if (!kvm_arm_vcpu_is_finalized(vcpu))
 		return -EPERM;
 
+	ret = kvm_arch_vcpu_run_map_fp(vcpu);
+	if (ret)
+		return ret;
+
+	if (likely(vcpu->arch.has_run_once))
+		return 0;
+
 	kvm_arm_vcpu_init_debug(vcpu);
 
 	if (likely(irqchip_in_kernel(kvm))) {
@@ -679,11 +691,6 @@ static void vcpu_req_sleep(struct kvm_vcpu *vcpu)
 	smp_rmb();
 }
 
-static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu)
-{
-	return vcpu->arch.target >= 0;
-}
-
 static void check_vcpu_requests(struct kvm_vcpu *vcpu)
 {
 	if (kvm_request_pending(vcpu)) {
@@ -779,13 +786,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 	struct kvm_run *run = vcpu->run;
 	int ret;
 
-	if (unlikely(!kvm_vcpu_initialized(vcpu)))
-		return -ENOEXEC;
-
-	ret = kvm_vcpu_first_run_init(vcpu);
-	if (ret)
-		return ret;
-
 	if (run->exit_reason == KVM_EXIT_MMIO) {
 		ret = kvm_handle_mmio_return(vcpu);
 		if (ret)
-- 
2.30.2


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[PATCH v2 5/5] KVM: arm64: Drop vcpu->arch.has_run_once for vcpu->pid

[Marc Zyngier]

With the transition to kvm_arch_vcpu_run_pid_change() to handle
the "run once" activities, it becomes obvious that has_run_once
is now an exact shadow of vcpu->pid.

Replace vcpu->arch.has_run_once with a new vcpu_has_run_once()
helper that directly checks for vcpu->pid, and get rid of the
now unused field.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_host.h | 5 ++---
 arch/arm64/kvm/arm.c              | 8 +++-----
 arch/arm64/kvm/vgic/vgic-init.c   | 2 +-
 3 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index d7107d627c54..e0de761ecbf2 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -366,9 +366,6 @@ struct kvm_vcpu_arch {
 	int target;
 	DECLARE_BITMAP(features, KVM_VCPU_MAX_FEATURES);
 
-	/* Detect first run of a vcpu */
-	bool has_run_once;
-
 	/* Virtual SError ESR to restore when HCR_EL2.VSE is set */
 	u64 vsesr_el2;
 
@@ -605,6 +602,8 @@ int __kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
 void kvm_arm_halt_guest(struct kvm *kvm);
 void kvm_arm_resume_guest(struct kvm *kvm);
 
+#define vcpu_has_run_once(vcpu)	!!rcu_access_pointer((vcpu)->pid)
+
 #ifndef __KVM_NVHE_HYPERVISOR__
 #define kvm_call_hyp_nvhe(f, ...)						\
 	({								\
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index a52f6a76485d..222aabd57147 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -350,7 +350,7 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
 
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
 {
-	if (vcpu->arch.has_run_once && unlikely(!irqchip_in_kernel(vcpu->kvm)))
+	if (vcpu_has_run_once(vcpu) && unlikely(!irqchip_in_kernel(vcpu->kvm)))
 		static_branch_dec(&userspace_irqchip_in_use);
 
 	kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
@@ -608,7 +608,7 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
 	if (ret)
 		return ret;
 
-	if (likely(vcpu->arch.has_run_once))
+	if (likely(vcpu_has_run_once(vcpu)))
 		return 0;
 
 	kvm_arm_vcpu_init_debug(vcpu);
@@ -639,8 +639,6 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
 		static_branch_inc(&userspace_irqchip_in_use);
 	}
 
-	vcpu->arch.has_run_once = true;
-
 	return ret;
 }
 
@@ -1123,7 +1121,7 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
 	 * need to invalidate the I-cache though, as FWB does *not*
 	 * imply CTR_EL0.DIC.
 	 */
-	if (vcpu->arch.has_run_once) {
+	if (vcpu_has_run_once(vcpu)) {
 		if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB))
 			stage2_unmap_vm(vcpu->kvm);
 		else
diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
index 340c51d87677..8d89ca15f613 100644
--- a/arch/arm64/kvm/vgic/vgic-init.c
+++ b/arch/arm64/kvm/vgic/vgic-init.c
@@ -91,7 +91,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
 		return ret;
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
-		if (vcpu->arch.has_run_once)
+		if (vcpu_has_run_once(vcpu))
 			goto out_unlock;
 	}
 	ret = 0;
-- 
2.30.2


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