RISC-V: KVM: Implement VCPU interrupts and requests handling

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.patel@wdc.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Alexander Graf <graf@amazon.com>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 0db663cf74e40163b47e9d29d50560731f150777..e307528bbdbf394571edfba6c2bf7bec354f64d0 100644 (file)
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -127,6 +127,21 @@ 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;
 
@@ -150,4 +165,12 @@ 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_interrupts(struct kvm_vcpu *vcpu, unsigned long mask);
+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 984d041a3e3b6abbfd6b0b4c759c9713036aa25f..3d3d703713c6cee040b8f42fb2693964fc7d4cb6 100644 (file)
--- 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/vcpu.c b/arch/riscv/kvm/vcpu.c
index 7b45aa23fba3116cb375dddfcb97a8259b5eed99..3342c73052652c5ab19e6a68c56c018a57644f4e 100644 (file)
--- 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>
@@ -57,6 +58,9 @@ 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);
 }
 
 int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id)
@@ -100,8 +104,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
 
 int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
 {
-       /* TODO: */
-       return 0;
+       return kvm_riscv_vcpu_has_interrupts(vcpu, 1UL << IRQ_VS_TIMER);
 }
 
 void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)
@@ -114,20 +117,18 @@ 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_interrupts(vcpu, -1UL) &&
+               !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;
 }
 
 vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
@@ -138,7 +139,21 @@ 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_VS_EXT);
+               else
+                       return kvm_riscv_vcpu_unset_interrupt(vcpu, IRQ_VS_EXT);
+       }
+
        return -ENOIOCTLCMD;
 }
 
@@ -187,18 +202,123 @@ 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->hvip &= ~mask;
+               csr->hvip |= val;
+       }
+}
+
+void kvm_riscv_vcpu_sync_interrupts(struct kvm_vcpu *vcpu)
+{
+       unsigned long hvip;
+       struct kvm_vcpu_arch *v = &vcpu->arch;
+       struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
+
+       /* Read current HVIP and VSIE CSRs */
+       csr->vsie = csr_read(CSR_VSIE);
+
+       /* Sync-up HVIP.VSSIP bit changes does by Guest */
+       hvip = csr_read(CSR_HVIP);
+       if ((csr->hvip ^ hvip) & (1UL << IRQ_VS_SOFT)) {
+               if (hvip & (1UL << IRQ_VS_SOFT)) {
+                       if (!test_and_set_bit(IRQ_VS_SOFT,
+                                             &v->irqs_pending_mask))
+                               set_bit(IRQ_VS_SOFT, &v->irqs_pending);
+               } else {
+                       if (!test_and_set_bit(IRQ_VS_SOFT,
+                                             &v->irqs_pending_mask))
+                               clear_bit(IRQ_VS_SOFT, &v->irqs_pending);
+               }
+       }
+}
+
+int kvm_riscv_vcpu_set_interrupt(struct kvm_vcpu *vcpu, unsigned int irq)
+{
+       if (irq != IRQ_VS_SOFT &&
+           irq != IRQ_VS_TIMER &&
+           irq != IRQ_VS_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_VS_SOFT &&
+           irq != IRQ_VS_TIMER &&
+           irq != IRQ_VS_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_interrupts(struct kvm_vcpu *vcpu, unsigned long mask)
+{
+       unsigned long ie = ((vcpu->arch.guest_csr.vsie & VSIP_VALID_MASK)
+                           << VSIP_TO_HVIP_SHIFT) & mask;
+
+       return (READ_ONCE(vcpu->arch.irqs_pending) & ie) ? 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,
@@ -222,7 +342,33 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 
 static void kvm_riscv_check_vcpu_requests(struct kvm_vcpu *vcpu)
 {
-       /* TODO: */
+       struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);
+
+       if (kvm_request_pending(vcpu)) {
+               if (kvm_check_request(KVM_REQ_SLEEP, vcpu)) {
+                       rcuwait_wait_event(wait,
+                               (!vcpu->arch.power_off) && (!vcpu->arch.pause),
+                               TASK_INTERRUPTIBLE);
+
+                       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_hvip(struct kvm_vcpu *vcpu)
+{
+       struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
+
+       csr_write(CSR_HVIP, csr->hvip);
 }
 
 int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
@@ -286,6 +432,15 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
                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 HVIP CSR for current CPU */
+               kvm_riscv_update_hvip(vcpu);
+
                if (ret <= 0 ||
                    kvm_request_pending(vcpu)) {
                        vcpu->mode = OUTSIDE_GUEST_MODE;
@@ -313,6 +468,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
                trap.htval = csr_read(CSR_HTVAL);
                trap.htinst = csr_read(CSR_HTINST);
 
+               /* 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