[PATCH v18 12/18] RISC-V: KVM: Add timer functionality

Anup Patel
2021-05-19T03:37:42Z

From: Atish Patra <atish.patra@wdc.com>

The RISC-V hypervisor specification doesn't have any virtual timer
feature.

Due to this, the guest VCPU timer will be programmed via SBI calls.
The host will use a separate hrtimer event for each guest VCPU to
provide timer functionality. We inject a virtual timer interrupt to
the guest VCPU whenever the guest VCPU hrtimer event expires.

This patch adds guest VCPU timer implementation along with ONE_REG
interface to access VCPU timer state from user space.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
arch/riscv/include/asm/kvm_host.h | 7 +
arch/riscv/include/asm/kvm_vcpu_timer.h | 44 +++++
arch/riscv/include/uapi/asm/kvm.h | 17 ++
arch/riscv/kvm/Makefile | 2 +-
arch/riscv/kvm/vcpu.c | 14 ++
arch/riscv/kvm/vcpu_timer.c | 225 ++++++++++++++++++++++++
arch/riscv/kvm/vm.c | 2 +-
drivers/clocksource/timer-riscv.c | 9 +
include/clocksource/timer-riscv.h | 16 ++
9 files changed, 334 insertions(+), 2 deletions(-)
create mode 100644 arch/riscv/include/asm/kvm_vcpu_timer.h
create mode 100644 arch/riscv/kvm/vcpu_timer.c
create mode 100644 include/clocksource/timer-riscv.h

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 51fe663b5093..0134201afb8c 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -12,6 +12,7 @@
#include <linux/types.h>
#include <linux/kvm.h>
#include <linux/kvm_types.h>
+#include <asm/kvm_vcpu_timer.h>

#ifdef CONFIG_64BIT
#define KVM_MAX_VCPUS (1U << 16)
@@ -65,6 +66,9 @@ struct kvm_arch {
/* stage2 page table */
pgd_t *pgd;
phys_addr_t pgd_phys;
+
+ /* Guest Timer */
+ struct kvm_guest_timer timer;
};

struct kvm_mmio_decode {
@@ -180,6 +184,9 @@ struct kvm_vcpu_arch {
unsigned long irqs_pending;
unsigned long irqs_pending_mask;

+ /* VCPU Timer */
+ struct kvm_vcpu_timer timer;
+
/* MMIO instruction details */
struct kvm_mmio_decode mmio_decode;

diff --git a/arch/riscv/include/asm/kvm_vcpu_timer.h b/arch/riscv/include/asm/kvm_vcpu_timer.h
new file mode 100644
index 000000000000..375281eb49e0
--- /dev/null
+++ b/arch/riscv/include/asm/kvm_vcpu_timer.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ * Atish Patra <atish.patra@wdc.com>
+ */
+
+#ifndef __KVM_VCPU_RISCV_TIMER_H
+#define __KVM_VCPU_RISCV_TIMER_H
+
+#include <linux/hrtimer.h>
+
+struct kvm_guest_timer {
+ /* Mult & Shift values to get nanoseconds from cycles */
+ u32 nsec_mult;
+ u32 nsec_shift;
+ /* Time delta value */
+ u64 time_delta;
+};
+
+struct kvm_vcpu_timer {
+ /* Flag for whether init is done */
+ bool init_done;
+ /* Flag for whether timer event is configured */
+ bool next_set;
+ /* Next timer event cycles */
+ u64 next_cycles;
+ /* Underlying hrtimer instance */
+ struct hrtimer hrt;
+};
+
+int kvm_riscv_vcpu_timer_next_event(struct kvm_vcpu *vcpu, u64 ncycles);
+int kvm_riscv_vcpu_get_reg_timer(struct kvm_vcpu *vcpu,
+ const struct kvm_one_reg *reg);
+int kvm_riscv_vcpu_set_reg_timer(struct kvm_vcpu *vcpu,
+ const struct kvm_one_reg *reg);
+int kvm_riscv_vcpu_timer_init(struct kvm_vcpu *vcpu);
+int kvm_riscv_vcpu_timer_deinit(struct kvm_vcpu *vcpu);
+int kvm_riscv_vcpu_timer_reset(struct kvm_vcpu *vcpu);
+void kvm_riscv_vcpu_timer_restore(struct kvm_vcpu *vcpu);
+int kvm_riscv_guest_timer_init(struct kvm *kvm);
+
+#endif
diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index f7e9dc388d54..08691dd27bcf 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -74,6 +74,18 @@ struct kvm_riscv_csr {
unsigned long scounteren;
};

+/* TIMER registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
+struct kvm_riscv_timer {
+ __u64 frequency;
+ __u64 time;
+ __u64 compare;
+ __u64 state;
+};
+
+/* Possible states for kvm_riscv_timer */
+#define KVM_RISCV_TIMER_STATE_OFF 0
+#define KVM_RISCV_TIMER_STATE_ON 1
+
#define KVM_REG_SIZE(id) \
(1U << (((id) & KVM_REG_SIZE_MASK) >> KVM_REG_SIZE_SHIFT))

@@ -96,6 +108,11 @@ struct kvm_riscv_csr {
#define KVM_REG_RISCV_CSR_REG(name) \
(offsetof(struct kvm_riscv_csr, name) / sizeof(unsigned long))

+/* Timer registers are mapped as type 4 */
+#define KVM_REG_RISCV_TIMER (0x04 << KVM_REG_RISCV_TYPE_SHIFT)
+#define KVM_REG_RISCV_TIMER_REG(name) \
+ (offsetof(struct kvm_riscv_timer, name) / sizeof(__u64))
+
#endif

#endif /* __LINUX_KVM_RISCV_H */
diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
index 98b294cbd96d..4f90443ab1ef 100644
--- a/arch/riscv/kvm/Makefile
+++ b/arch/riscv/kvm/Makefile
@@ -10,7 +10,7 @@ ccflags-y := -Ivirt/kvm -Iarch/riscv/kvm
kvm-objs := $(common-objs-y)

kvm-objs += main.o vm.o vmid.o tlb.o mmu.o
-kvm-objs += vcpu.o vcpu_exit.o vcpu_switch.o
+kvm-objs += vcpu.o vcpu_exit.o vcpu_switch.o vcpu_timer.o

obj-$(CONFIG_KVM) += kvm.o

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index cbaf14502c25..b6f19ca35562 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -55,6 +55,8 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)

memcpy(cntx, reset_cntx, sizeof(*cntx));

+ kvm_riscv_vcpu_timer_reset(vcpu);
+
WRITE_ONCE(vcpu->arch.irqs_pending, 0);
WRITE_ONCE(vcpu->arch.irqs_pending_mask, 0);
}
@@ -82,6 +84,9 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
cntx->hstatus |= HSTATUS_SPVP;
cntx->hstatus |= HSTATUS_SPV;

+ /* Setup VCPU timer */
+ kvm_riscv_vcpu_timer_init(vcpu);
+
/* Reset VCPU */
kvm_riscv_reset_vcpu(vcpu);

@@ -94,6 +99,9 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)

void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
{
+ /* Cleanup VCPU timer */
+ kvm_riscv_vcpu_timer_deinit(vcpu);
+
/* Flush the pages pre-allocated for Stage2 page table mappings */
kvm_riscv_stage2_flush_cache(vcpu);
}
@@ -334,6 +342,8 @@ static int kvm_riscv_vcpu_set_reg(struct kvm_vcpu *vcpu,
return kvm_riscv_vcpu_set_reg_core(vcpu, reg);
else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_CSR)
return kvm_riscv_vcpu_set_reg_csr(vcpu, reg);
+ else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_TIMER)
+ return kvm_riscv_vcpu_set_reg_timer(vcpu, reg);

return -EINVAL;
}
@@ -347,6 +357,8 @@ static int kvm_riscv_vcpu_get_reg(struct kvm_vcpu *vcpu,
return kvm_riscv_vcpu_get_reg_core(vcpu, reg);
else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_CSR)
return kvm_riscv_vcpu_get_reg_csr(vcpu, reg);
+ else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_TIMER)
+ return kvm_riscv_vcpu_get_reg_timer(vcpu, reg);

return -EINVAL;
}
@@ -579,6 +591,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)

kvm_riscv_stage2_update_hgatp(vcpu);

+ kvm_riscv_vcpu_timer_restore(vcpu);
+
vcpu->cpu = cpu;
}

diff --git a/arch/riscv/kvm/vcpu_timer.c b/arch/riscv/kvm/vcpu_timer.c
new file mode 100644
index 000000000000..ca08c420bf0a
--- /dev/null
+++ b/arch/riscv/kvm/vcpu_timer.c
@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ * Atish Patra <atish.patra@wdc.com>
+ */
+
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/kvm_host.h>
+#include <linux/uaccess.h>
+#include <clocksource/timer-riscv.h>
+#include <asm/kvm_csr.h>
+#include <asm/delay.h>
+#include <asm/kvm_vcpu_timer.h>
+
+static u64 kvm_riscv_current_cycles(struct kvm_guest_timer *gt)
+{
+ return get_cycles64() + gt->time_delta;
+}
+
+static u64 kvm_riscv_delta_cycles2ns(u64 cycles,
+ struct kvm_guest_timer *gt,
+ struct kvm_vcpu_timer *t)
+{
+ unsigned long flags;
+ u64 cycles_now, cycles_delta, delta_ns;
+
+ local_irq_save(flags);
+ cycles_now = kvm_riscv_current_cycles(gt);
+ if (cycles_now < cycles)
+ cycles_delta = cycles - cycles_now;
+ else
+ cycles_delta = 0;
+ delta_ns = (cycles_delta * gt->nsec_mult) >> gt->nsec_shift;
+ local_irq_restore(flags);
+
+ return delta_ns;
+}
+
+static enum hrtimer_restart kvm_riscv_vcpu_hrtimer_expired(struct hrtimer *h)
+{
+ u64 delta_ns;
+ struct kvm_vcpu_timer *t = container_of(h, struct kvm_vcpu_timer, hrt);
+ struct kvm_vcpu *vcpu = container_of(t, struct kvm_vcpu, arch.timer);
+ struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
+
+ if (kvm_riscv_current_cycles(gt) < t->next_cycles) {
+ delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t);
+ hrtimer_forward_now(&t->hrt, ktime_set(0, delta_ns));
+ return HRTIMER_RESTART;
+ }
+
+ t->next_set = false;
+ kvm_riscv_vcpu_set_interrupt(vcpu, IRQ_VS_TIMER);
+
+ return HRTIMER_NORESTART;
+}
+
+static int kvm_riscv_vcpu_timer_cancel(struct kvm_vcpu_timer *t)
+{
+ if (!t->init_done || !t->next_set)
+ return -EINVAL;
+
+ hrtimer_cancel(&t->hrt);
+ t->next_set = false;
+
+ return 0;
+}
+
+int kvm_riscv_vcpu_timer_next_event(struct kvm_vcpu *vcpu, u64 ncycles)
+{
+ struct kvm_vcpu_timer *t = &vcpu->arch.timer;
+ struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
+ u64 delta_ns;
+
+ if (!t->init_done)
+ return -EINVAL;
+
+ kvm_riscv_vcpu_unset_interrupt(vcpu, IRQ_VS_TIMER);
+
+ delta_ns = kvm_riscv_delta_cycles2ns(ncycles, gt, t);
+ t->next_cycles = ncycles;
+ hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL);
+ t->next_set = true;
+
+ return 0;
+}
+
+int kvm_riscv_vcpu_get_reg_timer(struct kvm_vcpu *vcpu,
+ const struct kvm_one_reg *reg)
+{
+ struct kvm_vcpu_timer *t = &vcpu->arch.timer;
+ struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
+ u64 __user *uaddr = (u64 __user *)(unsigned long)reg->addr;
+ unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
+ KVM_REG_SIZE_MASK |
+ KVM_REG_RISCV_TIMER);
+ u64 reg_val;
+
+ if (KVM_REG_SIZE(reg->id) != sizeof(u64))
+ return -EINVAL;
+ if (reg_num >= sizeof(struct kvm_riscv_timer) / sizeof(u64))
+ return -EINVAL;
+
+ switch (reg_num) {
+ case KVM_REG_RISCV_TIMER_REG(frequency):
+ reg_val = riscv_timebase;
+ break;
+ case KVM_REG_RISCV_TIMER_REG(time):
+ reg_val = kvm_riscv_current_cycles(gt);
+ break;
+ case KVM_REG_RISCV_TIMER_REG(compare):
+ reg_val = t->next_cycles;
+ break;
+ case KVM_REG_RISCV_TIMER_REG(state):
+ reg_val = (t->next_set) ? KVM_RISCV_TIMER_STATE_ON :
+ KVM_RISCV_TIMER_STATE_OFF;
+ break;
+ default:
+ return -EINVAL;
+ };
+
+ if (copy_to_user(uaddr, &reg_val, KVM_REG_SIZE(reg->id)))
+ return -EFAULT;
+
+ return 0;
+}
+
+int kvm_riscv_vcpu_set_reg_timer(struct kvm_vcpu *vcpu,
+ const struct kvm_one_reg *reg)
+{
+ struct kvm_vcpu_timer *t = &vcpu->arch.timer;
+ struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
+ u64 __user *uaddr = (u64 __user *)(unsigned long)reg->addr;
+ unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
+ KVM_REG_SIZE_MASK |
+ KVM_REG_RISCV_TIMER);
+ u64 reg_val;
+ int ret = 0;
+
+ if (KVM_REG_SIZE(reg->id) != sizeof(u64))
+ return -EINVAL;
+ if (reg_num >= sizeof(struct kvm_riscv_timer) / sizeof(u64))
+ return -EINVAL;
+
+ if (copy_from_user(&reg_val, uaddr, KVM_REG_SIZE(reg->id)))
+ return -EFAULT;
+
+ switch (reg_num) {
+ case KVM_REG_RISCV_TIMER_REG(frequency):
+ ret = -EOPNOTSUPP;
+ break;
+ case KVM_REG_RISCV_TIMER_REG(time):
+ gt->time_delta = reg_val - get_cycles64();
+ break;
+ case KVM_REG_RISCV_TIMER_REG(compare):
+ t->next_cycles = reg_val;
+ break;
+ case KVM_REG_RISCV_TIMER_REG(state):
+ if (reg_val == KVM_RISCV_TIMER_STATE_ON)
+ ret = kvm_riscv_vcpu_timer_next_event(vcpu, reg_val);
+ else
+ ret = kvm_riscv_vcpu_timer_cancel(t);
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ };
+
+ return ret;
+}
+
+int kvm_riscv_vcpu_timer_init(struct kvm_vcpu *vcpu)
+{
+ struct kvm_vcpu_timer *t = &vcpu->arch.timer;
+
+ if (t->init_done)
+ return -EINVAL;
+
+ hrtimer_init(&t->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ t->hrt.function = kvm_riscv_vcpu_hrtimer_expired;
+ t->init_done = true;
+ t->next_set = false;
+
+ return 0;
+}
+
+int kvm_riscv_vcpu_timer_deinit(struct kvm_vcpu *vcpu)
+{
+ int ret;
+
+ ret = kvm_riscv_vcpu_timer_cancel(&vcpu->arch.timer);
+ vcpu->arch.timer.init_done = false;
+
+ return ret;
+}
+
+int kvm_riscv_vcpu_timer_reset(struct kvm_vcpu *vcpu)
+{
+ return kvm_riscv_vcpu_timer_cancel(&vcpu->arch.timer);
+}
+
+void kvm_riscv_vcpu_timer_restore(struct kvm_vcpu *vcpu)
+{
+ struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
+
+#ifdef CONFIG_64BIT
+ csr_write(CSR_HTIMEDELTA, gt->time_delta);
+#else
+ csr_write(CSR_HTIMEDELTA, (u32)(gt->time_delta));
+ csr_write(CSR_HTIMEDELTAH, (u32)(gt->time_delta >> 32));
+#endif
+}
+
+int kvm_riscv_guest_timer_init(struct kvm *kvm)
+{
+ struct kvm_guest_timer *gt = &kvm->arch.timer;
+
+ riscv_cs_get_mult_shift(&gt->nsec_mult, &gt->nsec_shift);
+ gt->time_delta = -get_cycles64();
+
+ return 0;
+}
diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c
index 00a1a88008be..253c45ee20f9 100644
--- a/arch/riscv/kvm/vm.c
+++ b/arch/riscv/kvm/vm.c
@@ -26,7 +26,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
return r;
}

- return 0;
+ return kvm_riscv_guest_timer_init(kvm);
}

void kvm_arch_destroy_vm(struct kvm *kvm)
diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index c51c5ed15aa7..1767f8bf2013 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -13,10 +13,12 @@
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/irqdomain.h>
+#include <linux/module.h>
#include <linux/sched_clock.h>
#include <linux/io-64-nonatomic-lo-hi.h>
#include <linux/interrupt.h>
#include <linux/of_irq.h>
+#include <clocksource/timer-riscv.h>
#include <asm/smp.h>
#include <asm/sbi.h>
#include <asm/timex.h>
@@ -79,6 +81,13 @@ static int riscv_timer_dying_cpu(unsigned int cpu)
return 0;
}

+void riscv_cs_get_mult_shift(u32 *mult, u32 *shift)
+{
+ *mult = riscv_clocksource.mult;
+ *shift = riscv_clocksource.shift;
+}
+EXPORT_SYMBOL_GPL(riscv_cs_get_mult_shift);
+
/* called directly from the low-level interrupt handler */
static irqreturn_t riscv_timer_interrupt(int irq, void *dev_id)
{
diff --git a/include/clocksource/timer-riscv.h b/include/clocksource/timer-riscv.h
new file mode 100644
index 000000000000..d7f455754e60
--- /dev/null
+++ b/include/clocksource/timer-riscv.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ * Atish Patra <atish.patra@wdc.com>
+ */
+
+#ifndef __TIMER_RISCV_H
+#define __TIMER_RISCV_H
+
+#include <linux/types.h>
+
+extern void riscv_cs_get_mult_shift(u32 *mult, u32 *shift);
+
+#endif
--
2.25.1