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[v3,04/16] kvm: x86: Add support for activate/de-activate APICv at runtime

Message ID 1568401242-260374-5-git-send-email-suravee.suthikulpanit@amd.com (mailing list archive)
State New, archived
Headers show
Series kvm: x86: Support AMD SVM AVIC w/ in-kernel irqchip mode | expand

Commit Message

Suthikulpanit, Suravee Sept. 13, 2019, 7 p.m. UTC 
Certain runtime conditions require APICv to be temporary deactivated.
However, current implementation only support permanently deactivate
APICv at runtime (mainly used when running Hyper-V guest).

In addition, for AMD, when activate / deactivate APICv during runtime,
all vcpus in the VM has to be operating in the same APICv mode, which
requires the requesting (main) vcpu to notify others.

So, introduce interfaces to request all vcpus to activate/deactivate
APICv.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
 arch/x86/include/asm/kvm_host.h |  9 ++++
 arch/x86/kvm/x86.c              | 95 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 104 insertions(+)

Comments

Paolo Bonzini Oct. 9, 2019, 8:38 a.m. UTC | #1 
On 13/09/19 21:00, Suthikulpanit, Suravee wrote:
> +	kvm_for_each_vcpu(i, v, kvm)
> +		kvm_clear_request(KVM_REQ_APICV_DEACTIVATE, v);
> +
> +	if (kvm_x86_ops->pre_update_apicv_exec_ctrl)
> +		kvm_x86_ops->pre_update_apicv_exec_ctrl(vcpu, true);
> +
> +	kvm->arch.apicv_state = APICV_ACTIVATED;
> +
> +	kvm_make_all_cpus_request(kvm, KVM_REQ_APICV_ACTIVATE);
> +
> +	mutex_unlock(&kvm->arch.apicv_lock);

I think a lot of this logic can be simplified.  In particular, I would have:

- a single KVM_REQ_APICV_TOGGLE request that unifies
kvm_vcpu_activate_apicv and kvm_vcpu_deactivate_apicv.  The invariant is
that, at the end of the function, (vcpu->arch.apicv_active ==
(kvm->arch.apicv_state = APICV_ACTIVATED)).  The apicv_lock then becomes
an rwsem, so that kvm_activate_apic and kvm_deactivate_apic will
down_write it, while the processing of KVM_REQ_APICV_TOGGLE can
down_read it.

- the srcu_read_unlock/srcu_read_lock should be hidden in
svm_request_activate_avic/svm_request_deactivate_avic.  Everything else
should only take struct kvm*, following what you've started with patch
1.  In particular kvm_vcpu_deactivate_apicv should be changed to take a
struct kvm*, so that Hyper-V can do kvm_deactivate_apic(kvm,
APIC_DISABLED).  Hyper-V should not care about
srcu_read_lock/srcu_read_unlock.  avic_setup_access_page and
avic_destroy_access_page also can be changed to take struct kvm*.

Paolo
diff mbox series

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 562bfbd..a50fca1b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -78,6 +78,10 @@ 
 #define KVM_REQ_HV_STIMER		KVM_ARCH_REQ(22)
 #define KVM_REQ_LOAD_EOI_EXITMAP	KVM_ARCH_REQ(23)
 #define KVM_REQ_GET_VMCS12_PAGES	KVM_ARCH_REQ(24)
+#define KVM_REQ_APICV_ACTIVATE		\
+	KVM_ARCH_REQ_FLAGS(25, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
+#define KVM_REQ_APICV_DEACTIVATE	\
+	KVM_ARCH_REQ_FLAGS(26, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 
 #define CR0_RESERVED_BITS                                               \
 	(~(unsigned long)(X86_CR0_PE | X86_CR0_MP | X86_CR0_EM | X86_CR0_TS \
@@ -1098,6 +1102,8 @@  struct kvm_x86_ops {
 	void (*enable_irq_window)(struct kvm_vcpu *vcpu);
 	void (*update_cr8_intercept)(struct kvm_vcpu *vcpu, int tpr, int irr);
 	bool (*get_enable_apicv)(struct kvm *kvm);
+	void (*pre_update_apicv_exec_ctrl)(struct kvm_vcpu *vcpu,
+					   bool activate);
 	void (*refresh_apicv_exec_ctrl)(struct kvm_vcpu *vcpu);
 	void (*hwapic_irr_update)(struct kvm_vcpu *vcpu, int max_irr);
 	void (*hwapic_isr_update)(struct kvm_vcpu *vcpu, int isr);
@@ -1425,6 +1431,9 @@  gpa_t kvm_mmu_gva_to_gpa_system(struct kvm_vcpu *vcpu, gva_t gva,
 				struct x86_exception *exception);
 
 void kvm_vcpu_deactivate_apicv(struct kvm_vcpu *vcpu);
+void kvm_vcpu_activate_apicv(struct kvm_vcpu *vcpu);
+void kvm_make_apicv_activate_request(struct kvm_vcpu *vcpu);
+void kvm_make_apicv_deactivate_request(struct kvm_vcpu *vcpu, bool disable);
 
 int kvm_emulate_hypercall(struct kvm_vcpu *vcpu);
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 64d275e..446df2b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -26,6 +26,7 @@ 
 #include "cpuid.h"
 #include "pmu.h"
 #include "hyperv.h"
+#include "lapic.h"
 
 #include <linux/clocksource.h>
 #include <linux/interrupt.h>
@@ -7184,6 +7185,22 @@  static void kvm_pv_kick_cpu_op(struct kvm *kvm, unsigned long flags, int apicid)
 	kvm_irq_delivery_to_apic(kvm, NULL, &lapic_irq, NULL);
 }
 
+void kvm_vcpu_activate_apicv(struct kvm_vcpu *vcpu)
+{
+	if (!lapic_in_kernel(vcpu)) {
+		WARN_ON_ONCE(!vcpu->arch.apicv_active);
+		return;
+	}
+	if (vcpu->arch.apicv_active)
+		return;
+
+	vcpu->arch.apicv_active = true;
+	kvm_apic_update_apicv(vcpu);
+
+	kvm_x86_ops->refresh_apicv_exec_ctrl(vcpu);
+}
+EXPORT_SYMBOL_GPL(kvm_vcpu_activate_apicv);
+
 void kvm_vcpu_deactivate_apicv(struct kvm_vcpu *vcpu)
 {
 	if (!lapic_in_kernel(vcpu)) {
@@ -7194,8 +7211,10 @@  void kvm_vcpu_deactivate_apicv(struct kvm_vcpu *vcpu)
 		return;
 
 	vcpu->arch.apicv_active = false;
+	kvm_apic_update_apicv(vcpu);
 	kvm_x86_ops->refresh_apicv_exec_ctrl(vcpu);
 }
+EXPORT_SYMBOL_GPL(kvm_vcpu_deactivate_apicv);
 
 static void kvm_sched_yield(struct kvm *kvm, unsigned long dest_id)
 {
@@ -7711,6 +7730,78 @@  void kvm_make_scan_ioapic_request(struct kvm *kvm)
 	kvm_make_all_cpus_request(kvm, KVM_REQ_SCAN_IOAPIC);
 }
 
+/*
+ * NOTE:
+ * With kvm_make_apicv_[activate|deactivate]_request(), we could run into
+ * a situation where a vcpu tries to send a new request to a target vcpu before
+ * it can handle the prior request.
+ *
+ * For example:
+ *
+ *     vcpu0                                vcpu1
+ *
+ *     kvm_make_apicv_activate_request()    ...
+ *     Handle KVM_REQ_APICV_ACTIVATE        KVM_REQ_APICV_ACTIVATE==1
+ *     vcpu_run()                           ...
+ *     ...
+ *     ...
+ *     kvm_make_apicv_deactivate_request()  ...
+ *
+ * Here, vcpu0 would have to clear stale apicv activate/deactivate
+ * request before handling new one.
+ */
+void kvm_make_apicv_activate_request(struct kvm_vcpu *vcpu)
+{
+	int i;
+	struct kvm_vcpu *v;
+	struct kvm *kvm = vcpu->kvm;
+
+	mutex_lock(&kvm->arch.apicv_lock);
+	if (kvm->arch.apicv_state != APICV_SUSPENDED) {
+		mutex_unlock(&kvm->arch.apicv_lock);
+		return;
+	}
+
+	kvm_for_each_vcpu(i, v, kvm)
+		kvm_clear_request(KVM_REQ_APICV_DEACTIVATE, v);
+
+	if (kvm_x86_ops->pre_update_apicv_exec_ctrl)
+		kvm_x86_ops->pre_update_apicv_exec_ctrl(vcpu, true);
+
+	kvm->arch.apicv_state = APICV_ACTIVATED;
+
+	kvm_make_all_cpus_request(kvm, KVM_REQ_APICV_ACTIVATE);
+
+	mutex_unlock(&kvm->arch.apicv_lock);
+}
+EXPORT_SYMBOL_GPL(kvm_make_apicv_activate_request);
+
+void kvm_make_apicv_deactivate_request(struct kvm_vcpu *vcpu, bool disable)
+{
+	int i;
+	struct kvm_vcpu *v;
+	struct kvm *kvm = vcpu->kvm;
+
+	mutex_lock(&kvm->arch.apicv_lock);
+	if (kvm->arch.apicv_state != APICV_ACTIVATED) {
+		mutex_unlock(&kvm->arch.apicv_lock);
+		return;
+	}
+
+	kvm_for_each_vcpu(i, v, kvm)
+		kvm_clear_request(KVM_REQ_APICV_ACTIVATE, v);
+
+	if (kvm_x86_ops->pre_update_apicv_exec_ctrl)
+		kvm_x86_ops->pre_update_apicv_exec_ctrl(vcpu, false);
+
+	kvm->arch.apicv_state = disable ? APICV_DISABLED : APICV_SUSPENDED;
+
+	kvm_make_all_cpus_request(kvm, KVM_REQ_APICV_DEACTIVATE);
+
+	mutex_unlock(&kvm->arch.apicv_lock);
+}
+EXPORT_SYMBOL_GPL(kvm_make_apicv_deactivate_request);
+
 static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
 {
 	if (!kvm_apic_present(vcpu))
@@ -7897,6 +7988,10 @@  static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		 */
 		if (kvm_check_request(KVM_REQ_HV_STIMER, vcpu))
 			kvm_hv_process_stimers(vcpu);
+		if (kvm_check_request(KVM_REQ_APICV_ACTIVATE, vcpu))
+			kvm_vcpu_activate_apicv(vcpu);
+		if (kvm_check_request(KVM_REQ_APICV_DEACTIVATE, vcpu))
+			kvm_vcpu_deactivate_apicv(vcpu);
 	}
 
 	if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {