1 files changed, 319 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
new file mode 100644
index 000000000000..4a6d9a17da23
--- /dev/null
+++ b/arch/x86/kvm/vmx/posted_intr.c
@@ -0,0 +1,319 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kvm_host.h>
+#include <linux/kvm_irqfd.h>
+
+#include <asm/irq_remapping.h>
+#include <asm/cpu.h>
+
+#include "lapic.h"
+#include "irq.h"
+#include "posted_intr.h"
+#include "trace.h"
+#include "vmx.h"
+#include "tdx.h"
+
+/*
+ * Maintain a per-CPU list of vCPUs that need to be awakened by wakeup_handler()
+ * when a WAKEUP_VECTOR interrupted is posted.  vCPUs are added to the list when
+ * the vCPU is scheduled out and is blocking (e.g. in HLT) with IRQs enabled.
+ * The vCPUs posted interrupt descriptor is updated at the same time to set its
+ * notification vector to WAKEUP_VECTOR, so that posted interrupt from devices
+ * wake the target vCPUs.  vCPUs are removed from the list and the notification
+ * vector is reset when the vCPU is scheduled in.
+ */
+static DEFINE_PER_CPU(struct list_head, wakeup_vcpus_on_cpu);
+/*
+ * Protect the per-CPU list with a per-CPU spinlock to handle task migration.
+ * When a blocking vCPU is awakened _and_ migrated to a different pCPU, the
+ * ->sched_in() path will need to take the vCPU off the list of the _previous_
+ * CPU.  IRQs must be disabled when taking this lock, otherwise deadlock will
+ * occur if a wakeup IRQ arrives and attempts to acquire the lock.
+ */
+static DEFINE_PER_CPU(raw_spinlock_t, wakeup_vcpus_on_cpu_lock);
+
+#define PI_LOCK_SCHED_OUT SINGLE_DEPTH_NESTING
+
+static struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu)
+{
+	return &(to_vt(vcpu)->pi_desc);
+}
+
+static int pi_try_set_control(struct pi_desc *pi_desc, u64 *pold, u64 new)
+{
+	/*
+	 * PID.ON can be set at any time by a different vCPU or by hardware,
+	 * e.g. a device.  PID.control must be written atomically, and the
+	 * update must be retried with a fresh snapshot an ON change causes
+	 * the cmpxchg to fail.
+	 */
+	if (!try_cmpxchg64(&pi_desc->control, pold, new))
+		return -EBUSY;
+
+	return 0;
+}
+
+void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
+{
+	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
+	struct vcpu_vt *vt = to_vt(vcpu);
+	struct pi_desc old, new;
+	unsigned long flags;
+	unsigned int dest;
+
+	/*
+	 * To simplify hot-plug and dynamic toggling of APICv, keep PI.NDST and
+	 * PI.SN up-to-date even if there is no assigned device or if APICv is
+	 * deactivated due to a dynamic inhibit bit, e.g. for Hyper-V's SyncIC.
+	 */
+	if (!enable_apicv || !lapic_in_kernel(vcpu))
+		return;
+
+	/*
+	 * If the vCPU wasn't on the wakeup list and wasn't migrated, then the
+	 * full update can be skipped as neither the vector nor the destination
+	 * needs to be changed.  Clear SN even if there is no assigned device,
+	 * again for simplicity.
+	 */
+	if (pi_desc->nv != POSTED_INTR_WAKEUP_VECTOR && vcpu->cpu == cpu) {
+		if (pi_test_and_clear_sn(pi_desc))
+			goto after_clear_sn;
+		return;
+	}
+
+	local_irq_save(flags);
+
+	/*
+	 * If the vCPU was waiting for wakeup, remove the vCPU from the wakeup
+	 * list of the _previous_ pCPU, which will not be the same as the
+	 * current pCPU if the task was migrated.
+	 */
+	if (pi_desc->nv == POSTED_INTR_WAKEUP_VECTOR) {
+		raw_spinlock_t *spinlock = &per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu);
+
+		/*
+		 * In addition to taking the wakeup lock for the regular/IRQ
+		 * context, tell lockdep it is being taken for the "sched out"
+		 * context as well.  vCPU loads happens in task context, and
+		 * this is taking the lock of the *previous* CPU, i.e. can race
+		 * with both the scheduler and the wakeup handler.
+		 */
+		raw_spin_lock(spinlock);
+		spin_acquire(&spinlock->dep_map, PI_LOCK_SCHED_OUT, 0, _RET_IP_);
+		list_del(&vt->pi_wakeup_list);
+		spin_release(&spinlock->dep_map, _RET_IP_);
+		raw_spin_unlock(spinlock);
+	}
+
+	dest = cpu_physical_id(cpu);
+	if (!x2apic_mode)
+		dest = (dest << 8) & 0xFF00;
+
+	old.control = READ_ONCE(pi_desc->control);
+	do {
+		new.control = old.control;
+
+		/*
+		 * Clear SN (as above) and refresh the destination APIC ID to
+		 * handle task migration (@cpu != vcpu->cpu).
+		 */
+		new.ndst = dest;
+		__pi_clear_sn(&new);
+
+		/*
+		 * Restore the notification vector; in the blocking case, the
+		 * descriptor was modified on "put" to use the wakeup vector.
+		 */
+		new.nv = POSTED_INTR_VECTOR;
+	} while (pi_try_set_control(pi_desc, &old.control, new.control));
+
+	local_irq_restore(flags);
+
+after_clear_sn:
+
+	/*
+	 * Clear SN before reading the bitmap.  The VT-d firmware
+	 * writes the bitmap and reads SN atomically (5.2.3 in the
+	 * spec), so it doesn't really have a memory barrier that
+	 * pairs with this, but we cannot do that and we need one.
+	 */
+	smp_mb__after_atomic();
+
+	if (!pi_is_pir_empty(pi_desc))
+		pi_set_on(pi_desc);
+}
+
+static bool vmx_can_use_vtd_pi(struct kvm *kvm)
+{
+	/*
+	 * Note, reading the number of possible bypass IRQs can race with a
+	 * bypass IRQ being attached to the VM.  vmx_pi_start_bypass() ensures
+	 * blockng vCPUs will see an elevated count or get KVM_REQ_UNBLOCK.
+	 */
+	return irqchip_in_kernel(kvm) && kvm_arch_has_irq_bypass() &&
+	       READ_ONCE(kvm->arch.nr_possible_bypass_irqs);
+}
+
+/*
+ * Put the vCPU on this pCPU's list of vCPUs that needs to be awakened and set
+ * WAKEUP as the notification vector in the PI descriptor.
+ */
+static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu)
+{
+	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
+	struct vcpu_vt *vt = to_vt(vcpu);
+	struct pi_desc old, new;
+
+	lockdep_assert_irqs_disabled();
+
+	/*
+	 * Acquire the wakeup lock using the "sched out" context to workaround
+	 * a lockdep false positive.  When this is called, schedule() holds
+	 * various per-CPU scheduler locks.  When the wakeup handler runs, it
+	 * holds this CPU's wakeup lock while calling try_to_wake_up(), which
+	 * can eventually take the aforementioned scheduler locks, which causes
+	 * lockdep to assume there is deadlock.
+	 *
+	 * Deadlock can't actually occur because IRQs are disabled for the
+	 * entirety of the sched_out critical section, i.e. the wakeup handler
+	 * can't run while the scheduler locks are held.
+	 */
+	raw_spin_lock_nested(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu),
+			     PI_LOCK_SCHED_OUT);
+	list_add_tail(&vt->pi_wakeup_list,
+		      &per_cpu(wakeup_vcpus_on_cpu, vcpu->cpu));
+	raw_spin_unlock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu));
+
+	WARN(pi_test_sn(pi_desc), "PI descriptor SN field set before blocking");
+
+	old.control = READ_ONCE(pi_desc->control);
+	do {
+		/* set 'NV' to 'wakeup vector' */
+		new.control = old.control;
+		new.nv = POSTED_INTR_WAKEUP_VECTOR;
+	} while (pi_try_set_control(pi_desc, &old.control, new.control));
+
+	/*
+	 * Send a wakeup IPI to this CPU if an interrupt may have been posted
+	 * before the notification vector was updated, in which case the IRQ
+	 * will arrive on the non-wakeup vector.  An IPI is needed as calling
+	 * try_to_wake_up() from ->sched_out() isn't allowed (IRQs are not
+	 * enabled until it is safe to call try_to_wake_up() on the task being
+	 * scheduled out).
+	 */
+	if (pi_test_on(&new))
+		__apic_send_IPI_self(POSTED_INTR_WAKEUP_VECTOR);
+}
+
+static bool vmx_needs_pi_wakeup(struct kvm_vcpu *vcpu)
+{
+	/*
+	 * The default posted interrupt vector does nothing when
+	 * invoked outside guest mode.   Return whether a blocked vCPU
+	 * can be the target of posted interrupts, as is the case when
+	 * using either IPI virtualization or VT-d PI, so that the
+	 * notification vector is switched to the one that calls
+	 * back to the pi_wakeup_handler() function.
+	 */
+	return (vmx_can_use_ipiv(vcpu) && !is_td_vcpu(vcpu)) ||
+		vmx_can_use_vtd_pi(vcpu->kvm);
+}
+
+void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu)
+{
+	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
+
+	if (!vmx_needs_pi_wakeup(vcpu))
+		return;
+
+	/*
+	 * If the vCPU is blocking with IRQs enabled and ISN'T being preempted,
+	 * enable the wakeup handler so that notification IRQ wakes the vCPU as
+	 * expected.  There is no need to enable the wakeup handler if the vCPU
+	 * is preempted between setting its wait state and manually scheduling
+	 * out, as the task is still runnable, i.e. doesn't need a wake event
+	 * from KVM to be scheduled in.
+	 *
+	 * If the wakeup handler isn't being enabled, Suppress Notifications as
+	 * the cost of propagating PIR.IRR to PID.ON is negligible compared to
+	 * the cost of a spurious IRQ, and vCPU put/load is a slow path.
+	 */
+	if (!vcpu->preempted && kvm_vcpu_is_blocking(vcpu) &&
+	    ((is_td_vcpu(vcpu) && tdx_interrupt_allowed(vcpu)) ||
+	     (!is_td_vcpu(vcpu) && !vmx_interrupt_blocked(vcpu))))
+		pi_enable_wakeup_handler(vcpu);
+	else
+		pi_set_sn(pi_desc);
+}
+
+/*
+ * Handler for POSTED_INTERRUPT_WAKEUP_VECTOR.
+ */
+void pi_wakeup_handler(void)
+{
+	int cpu = smp_processor_id();
+	struct list_head *wakeup_list = &per_cpu(wakeup_vcpus_on_cpu, cpu);
+	raw_spinlock_t *spinlock = &per_cpu(wakeup_vcpus_on_cpu_lock, cpu);
+	struct vcpu_vt *vt;
+
+	raw_spin_lock(spinlock);
+	list_for_each_entry(vt, wakeup_list, pi_wakeup_list) {
+
+		if (pi_test_on(&vt->pi_desc))
+			kvm_vcpu_wake_up(vt_to_vcpu(vt));
+	}
+	raw_spin_unlock(spinlock);
+}
+
+void __init pi_init_cpu(int cpu)
+{
+	INIT_LIST_HEAD(&per_cpu(wakeup_vcpus_on_cpu, cpu));
+	raw_spin_lock_init(&per_cpu(wakeup_vcpus_on_cpu_lock, cpu));
+}
+
+void pi_apicv_pre_state_restore(struct kvm_vcpu *vcpu)
+{
+	struct pi_desc *pi = vcpu_to_pi_desc(vcpu);
+
+	pi_clear_on(pi);
+	memset(pi->pir, 0, sizeof(pi->pir));
+}
+
+bool pi_has_pending_interrupt(struct kvm_vcpu *vcpu)
+{
+	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
+
+	return pi_test_on(pi_desc) ||
+		(pi_test_sn(pi_desc) && !pi_is_pir_empty(pi_desc));
+}
+
+
+/*
+ * Kick all vCPUs when the first possible bypass IRQ is attached to a VM, as
+ * blocking vCPUs may scheduled out without reconfiguring PID.NV to the wakeup
+ * vector, i.e. if the bypass IRQ came along after vmx_vcpu_pi_put().
+ */
+void vmx_pi_start_bypass(struct kvm *kvm)
+{
+	if (WARN_ON_ONCE(!vmx_can_use_vtd_pi(kvm)))
+		return;
+
+	kvm_make_all_cpus_request(kvm, KVM_REQ_UNBLOCK);
+}
+
+int vmx_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
+		       unsigned int host_irq, uint32_t guest_irq,
+		       struct kvm_vcpu *vcpu, u32 vector)
+{
+	if (vcpu) {
+		struct intel_iommu_pi_data pi_data = {
+			.pi_desc_addr = __pa(vcpu_to_pi_desc(vcpu)),
+			.vector = vector,
+		};
+
+		return irq_set_vcpu_affinity(host_irq, &pi_data);
+	} else {
+		return irq_set_vcpu_affinity(host_irq, NULL);
+	}
+}