This patch implements VCPU interrupts and requests which are both
asynchronous events.

The VCPU interrupts can be set/unset using KVM_INTERRUPT ioctl from
user-space. In future, the in-kernel IRQCHIP emulation will use
kvm_riscv_vcpu_set_interrupt() and kvm_riscv_vcpu_unset_interrupt()
functions to set/unset VCPU interrupts.

Important VCPU requests implemented by this patch are:
KVM_REQ_SLEEP       - set whenever VCPU itself goes to sleep state
KVM_REQ_VCPU_RESET  - set whenever VCPU reset is requested

The WFI trap-n-emulate (added later) will use KVM_REQ_SLEEP request
and kvm_riscv_vcpu_has_interrupt() function.

The KVM_REQ_VCPU_RESET request will be used by SBI emulation (added
later) to power-up a VCPU in power-off state. The user-space can use
the GET_MPSTATE/SET_MPSTATE ioctls to get/set power state of a VCPU.

Signed-off-by: Anup Patel <anup.pa...@wdc.com>
---
 arch/riscv/include/asm/kvm_host.h |  26 +++++
 arch/riscv/include/uapi/asm/kvm.h |   3 +
 arch/riscv/kvm/main.c             |   8 ++
 arch/riscv/kvm/vcpu.c             | 184 +++++++++++++++++++++++++++---
 4 files changed, 208 insertions(+), 13 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_host.h 
b/arch/riscv/include/asm/kvm_host.h
index dab32c9c3470..d801216da6d0 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -122,6 +122,21 @@ struct kvm_vcpu_arch {
        /* CPU CSR context upon Guest VCPU reset */
        struct kvm_vcpu_csr guest_reset_csr;
 
+       /*
+        * VCPU interrupts
+        *
+        * We have a lockless approach for tracking pending VCPU interrupts
+        * implemented using atomic bitops. The irqs_pending bitmap represent
+        * pending interrupts whereas irqs_pending_mask represent bits changed
+        * in irqs_pending. Our approach is modeled around multiple producer
+        * and single consumer problem where the consumer is the VCPU itself.
+        */
+       unsigned long irqs_pending;
+       unsigned long irqs_pending_mask;
+
+       /* VCPU power-off state */
+       bool power_off;
+
        /* Don't run the VCPU (blocked) */
        bool pause;
 
@@ -135,6 +150,9 @@ static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu 
*vcpu) {}
 static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
 static inline void kvm_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}
 
+int kvm_riscv_setup_vsip(void);
+void kvm_riscv_cleanup_vsip(void);
+
 void kvm_riscv_stage2_flush_cache(struct kvm_vcpu *vcpu);
 int kvm_riscv_stage2_alloc_pgd(struct kvm *kvm);
 void kvm_riscv_stage2_free_pgd(struct kvm *kvm);
@@ -146,4 +164,12 @@ int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct 
kvm_run *run,
 
 static inline void __kvm_riscv_switch_to(struct kvm_vcpu_arch *vcpu_arch) {}
 
+int kvm_riscv_vcpu_set_interrupt(struct kvm_vcpu *vcpu, unsigned int irq);
+int kvm_riscv_vcpu_unset_interrupt(struct kvm_vcpu *vcpu, unsigned int irq);
+void kvm_riscv_vcpu_flush_interrupts(struct kvm_vcpu *vcpu);
+void kvm_riscv_vcpu_sync_interrupts(struct kvm_vcpu *vcpu);
+bool kvm_riscv_vcpu_has_interrupt(struct kvm_vcpu *vcpu);
+void kvm_riscv_vcpu_power_off(struct kvm_vcpu *vcpu);
+void kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu);
+
 #endif /* __RISCV_KVM_HOST_H__ */
diff --git a/arch/riscv/include/uapi/asm/kvm.h 
b/arch/riscv/include/uapi/asm/kvm.h
index d15875818b6e..6dbc056d58ba 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -18,6 +18,9 @@
 
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
 
+#define KVM_INTERRUPT_SET      -1U
+#define KVM_INTERRUPT_UNSET    -2U
+
 /* for KVM_GET_REGS and KVM_SET_REGS */
 struct kvm_regs {
 };
diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
index e1ffe6d42f39..d088247843c5 100644
--- a/arch/riscv/kvm/main.c
+++ b/arch/riscv/kvm/main.c
@@ -48,6 +48,8 @@ int kvm_arch_hardware_enable(void)
        hideleg |= SIE_SEIE;
        csr_write(CSR_HIDELEG, hideleg);
 
+       csr_write(CSR_VSIP, 0);
+
        return 0;
 }
 
@@ -59,11 +61,17 @@ void kvm_arch_hardware_disable(void)
 
 int kvm_arch_init(void *opaque)
 {
+       int ret;
+
        if (!riscv_isa_extension_available(NULL, h)) {
                kvm_info("hypervisor extension not available\n");
                return -ENODEV;
        }
 
+       ret = kvm_riscv_setup_vsip();
+       if (ret)
+               return ret;
+
        kvm_info("hypervisor extension available\n");
 
        return 0;
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 8272b05d6ce4..7f59e85c6af8 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -11,6 +11,7 @@
 #include <linux/err.h>
 #include <linux/kdebug.h>
 #include <linux/module.h>
+#include <linux/percpu.h>
 #include <linux/uaccess.h>
 #include <linux/vmalloc.h>
 #include <linux/sched/signal.h>
@@ -40,6 +41,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
                                 riscv_isa_extension_mask(s) | \
                                 riscv_isa_extension_mask(u))
 
+static unsigned long __percpu *vsip_shadow;
+
 static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
 {
        struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
@@ -50,6 +53,9 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
        memcpy(csr, reset_csr, sizeof(*csr));
 
        memcpy(cntx, reset_cntx, sizeof(*cntx));
+
+       WRITE_ONCE(vcpu->arch.irqs_pending, 0);
+       WRITE_ONCE(vcpu->arch.irqs_pending_mask, 0);
 }
 
 struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id)
@@ -116,8 +122,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
 
 int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
 {
-       /* TODO: */
-       return 0;
+       return READ_ONCE(vcpu->arch.irqs_pending) & (1UL << IRQ_S_TIMER);
 }
 
 void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)
@@ -130,20 +135,18 @@ void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu)
 
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 {
-       /* TODO: */
-       return 0;
+       return (kvm_riscv_vcpu_has_interrupt(vcpu) &&
+               !vcpu->arch.power_off && !vcpu->arch.pause);
 }
 
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
-       /* TODO: */
-       return 0;
+       return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
 }
 
 bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
 {
-       /* TODO: */
-       return false;
+       return (vcpu->arch.guest_context.sstatus & SR_SPP) ? true : false;
 }
 
 bool kvm_arch_has_vcpu_debugfs(void)
@@ -164,7 +167,21 @@ vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, 
struct vm_fault *vmf)
 long kvm_arch_vcpu_async_ioctl(struct file *filp,
                               unsigned int ioctl, unsigned long arg)
 {
-       /* TODO; */
+       struct kvm_vcpu *vcpu = filp->private_data;
+       void __user *argp = (void __user *)arg;
+
+       if (ioctl == KVM_INTERRUPT) {
+               struct kvm_interrupt irq;
+
+               if (copy_from_user(&irq, argp, sizeof(irq)))
+                       return -EFAULT;
+
+               if (irq.irq == KVM_INTERRUPT_SET)
+                       return kvm_riscv_vcpu_set_interrupt(vcpu, IRQ_S_EXT);
+               else
+                       return kvm_riscv_vcpu_unset_interrupt(vcpu, IRQ_S_EXT);
+       }
+
        return -ENOIOCTLCMD;
 }
 
@@ -213,18 +230,103 @@ int kvm_arch_vcpu_ioctl_set_regs(struct kvm_vcpu *vcpu, 
struct kvm_regs *regs)
        return -EINVAL;
 }
 
+void kvm_riscv_vcpu_flush_interrupts(struct kvm_vcpu *vcpu)
+{
+       struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
+       unsigned long mask, val;
+
+       if (READ_ONCE(vcpu->arch.irqs_pending_mask)) {
+               mask = xchg_acquire(&vcpu->arch.irqs_pending_mask, 0);
+               val = READ_ONCE(vcpu->arch.irqs_pending) & mask;
+
+               csr->vsip &= ~mask;
+               csr->vsip |= val;
+       }
+}
+
+void kvm_riscv_vcpu_sync_interrupts(struct kvm_vcpu *vcpu)
+{
+       vcpu->arch.guest_csr.vsip = csr_read(CSR_VSIP);
+       vcpu->arch.guest_csr.vsie = csr_read(CSR_VSIE);
+}
+
+int kvm_riscv_vcpu_set_interrupt(struct kvm_vcpu *vcpu, unsigned int irq)
+{
+       if (irq != IRQ_S_SOFT &&
+           irq != IRQ_S_TIMER &&
+           irq != IRQ_S_EXT)
+               return -EINVAL;
+
+       set_bit(irq, &vcpu->arch.irqs_pending);
+       smp_mb__before_atomic();
+       set_bit(irq, &vcpu->arch.irqs_pending_mask);
+
+       kvm_vcpu_kick(vcpu);
+
+       return 0;
+}
+
+int kvm_riscv_vcpu_unset_interrupt(struct kvm_vcpu *vcpu, unsigned int irq)
+{
+       if (irq != IRQ_S_SOFT &&
+           irq != IRQ_S_TIMER &&
+           irq != IRQ_S_EXT)
+               return -EINVAL;
+
+       clear_bit(irq, &vcpu->arch.irqs_pending);
+       smp_mb__before_atomic();
+       set_bit(irq, &vcpu->arch.irqs_pending_mask);
+
+       return 0;
+}
+
+bool kvm_riscv_vcpu_has_interrupt(struct kvm_vcpu *vcpu)
+{
+       return (READ_ONCE(vcpu->arch.irqs_pending) &
+               vcpu->arch.guest_csr.vsie) ? true : false;
+}
+
+void kvm_riscv_vcpu_power_off(struct kvm_vcpu *vcpu)
+{
+       vcpu->arch.power_off = true;
+       kvm_make_request(KVM_REQ_SLEEP, vcpu);
+       kvm_vcpu_kick(vcpu);
+}
+
+void kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu)
+{
+       vcpu->arch.power_off = false;
+       kvm_vcpu_wake_up(vcpu);
+}
+
 int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
                                    struct kvm_mp_state *mp_state)
 {
-       /* TODO: */
+       if (vcpu->arch.power_off)
+               mp_state->mp_state = KVM_MP_STATE_STOPPED;
+       else
+               mp_state->mp_state = KVM_MP_STATE_RUNNABLE;
+
        return 0;
 }
 
 int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
                                    struct kvm_mp_state *mp_state)
 {
-       /* TODO: */
-       return 0;
+       int ret = 0;
+
+       switch (mp_state->mp_state) {
+       case KVM_MP_STATE_RUNNABLE:
+               vcpu->arch.power_off = false;
+               break;
+       case KVM_MP_STATE_STOPPED:
+               kvm_riscv_vcpu_power_off(vcpu);
+               break;
+       default:
+               ret = -EINVAL;
+       }
+
+       return ret;
 }
 
 int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
@@ -248,7 +350,51 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 
 static void kvm_riscv_check_vcpu_requests(struct kvm_vcpu *vcpu)
 {
-       /* TODO: */
+       struct swait_queue_head *wq = kvm_arch_vcpu_wq(vcpu);
+
+       if (kvm_request_pending(vcpu)) {
+               if (kvm_check_request(KVM_REQ_SLEEP, vcpu)) {
+                       swait_event_interruptible_exclusive(*wq,
+                                               ((!vcpu->arch.power_off) &&
+                                               (!vcpu->arch.pause)));
+
+                       if (vcpu->arch.power_off || vcpu->arch.pause) {
+                               /*
+                                * Awaken to handle a signal, request to
+                                * sleep again later.
+                                */
+                               kvm_make_request(KVM_REQ_SLEEP, vcpu);
+                       }
+               }
+
+               if (kvm_check_request(KVM_REQ_VCPU_RESET, vcpu))
+                       kvm_riscv_reset_vcpu(vcpu);
+       }
+}
+
+static void kvm_riscv_update_vsip(struct kvm_vcpu *vcpu)
+{
+       struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
+       unsigned long *vsip = raw_cpu_ptr(vsip_shadow);
+
+       if (*vsip != csr->vsip) {
+               csr_write(CSR_VSIP, csr->vsip);
+               *vsip = csr->vsip;
+       }
+}
+
+int kvm_riscv_setup_vsip(void)
+{
+       vsip_shadow = alloc_percpu(unsigned long);
+       if (!vsip_shadow)
+               return -ENOMEM;
+
+       return 0;
+}
+
+void kvm_riscv_cleanup_vsip(void)
+{
+       free_percpu(vsip_shadow);
 }
 
 int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
@@ -311,6 +457,15 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct 
kvm_run *run)
                srcu_read_unlock(&vcpu->kvm->srcu, vcpu->arch.srcu_idx);
                smp_mb__after_srcu_read_unlock();
 
+               /*
+                * We might have got VCPU interrupts updated asynchronously
+                * so update it in HW.
+                */
+               kvm_riscv_vcpu_flush_interrupts(vcpu);
+
+               /* Update VSIP CSR for current CPU */
+               kvm_riscv_update_vsip(vcpu);
+
                if (ret <= 0 ||
                    kvm_request_pending(vcpu)) {
                        vcpu->mode = OUTSIDE_GUEST_MODE;
@@ -334,6 +489,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct 
kvm_run *run)
                scause = csr_read(CSR_SCAUSE);
                stval = csr_read(CSR_STVAL);
 
+               /* Syncup interrupts state with HW */
+               kvm_riscv_vcpu_sync_interrupts(vcpu);
+
                /*
                 * We may have taken a host interrupt in VS/VU-mode (i.e.
                 * while executing the guest). This interrupt is still
-- 
2.17.1

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