Merge tag 'loongarch-kvm-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson into HEAD

LoongArch KVM changes for v6.7

Add LoongArch's KVM support. Loongson 3A5000/3A6000 supports hardware
assisted virtualization. With cpu virtualization, there are separate
hw-supported user mode and kernel mode in guest mode. With memory
virtualization, there are two-level hw mmu table for guest mode and host
mode. Also there is separate hw cpu timer with consant frequency in
guest mode, so that vm can migrate between hosts with different freq.
Currently, we are able to boot LoongArch Linux Guests.

Few key aspects of KVM LoongArch added by this series are:
1. Enable kvm hardware function when kvm module is loaded.
2. Implement VM and vcpu related ioctl interface such as vcpu create,
   vcpu run etc. GET_ONE_REG/SET_ONE_REG ioctl commands are use to
   get general registers one by one.
3. Hardware access about MMU, timer and csr are emulated in kernel.
4. Hardwares such as mmio and iocsr device are emulated in user space
   such as IPI, irqchips, pci devices etc.

1 files changed, 197 insertions, 0 deletions

diff --git a/arch/loongarch/kvm/timer.c b/arch/loongarch/kvm/timer.c
new file mode 100644
index 000000000000..284bf553fefe
--- /dev/null
+++ b/arch/loongarch/kvm/timer.c
@@ -0,0 +1,197 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020-2023 Loongson Technology Corporation Limited
+ */
+
+#include <linux/kvm_host.h>
+#include <asm/kvm_csr.h>
+#include <asm/kvm_vcpu.h>
+
+/*
+ * ktime_to_tick() - Scale ktime_t to timer tick value.
+ */
+static inline u64 ktime_to_tick(struct kvm_vcpu *vcpu, ktime_t now)
+{
+	u64 delta;
+
+	delta = ktime_to_ns(now);
+	return div_u64(delta * vcpu->arch.timer_mhz, MNSEC_PER_SEC);
+}
+
+static inline u64 tick_to_ns(struct kvm_vcpu *vcpu, u64 tick)
+{
+	return div_u64(tick * MNSEC_PER_SEC, vcpu->arch.timer_mhz);
+}
+
+/*
+ * Push timer forward on timeout.
+ * Handle an hrtimer event by push the hrtimer forward a period.
+ */
+static enum hrtimer_restart kvm_count_timeout(struct kvm_vcpu *vcpu)
+{
+	unsigned long cfg, period;
+
+	/* Add periodic tick to current expire time */
+	cfg = kvm_read_sw_gcsr(vcpu->arch.csr, LOONGARCH_CSR_TCFG);
+	if (cfg & CSR_TCFG_PERIOD) {
+		period = tick_to_ns(vcpu, cfg & CSR_TCFG_VAL);
+		hrtimer_add_expires_ns(&vcpu->arch.swtimer, period);
+		return HRTIMER_RESTART;
+	} else
+		return HRTIMER_NORESTART;
+}
+
+/* Low level hrtimer wake routine */
+enum hrtimer_restart kvm_swtimer_wakeup(struct hrtimer *timer)
+{
+	struct kvm_vcpu *vcpu;
+
+	vcpu = container_of(timer, struct kvm_vcpu, arch.swtimer);
+	kvm_queue_irq(vcpu, INT_TI);
+	rcuwait_wake_up(&vcpu->wait);
+
+	return kvm_count_timeout(vcpu);
+}
+
+/*
+ * Initialise the timer to the specified frequency, zero it
+ */
+void kvm_init_timer(struct kvm_vcpu *vcpu, unsigned long timer_hz)
+{
+	vcpu->arch.timer_mhz = timer_hz >> 20;
+
+	/* Starting at 0 */
+	kvm_write_sw_gcsr(vcpu->arch.csr, LOONGARCH_CSR_TVAL, 0);
+}
+
+/*
+ * Restore hard timer state and enable guest to access timer registers
+ * without trap, should be called with irq disabled
+ */
+void kvm_acquire_timer(struct kvm_vcpu *vcpu)
+{
+	unsigned long cfg;
+
+	cfg = read_csr_gcfg();
+	if (!(cfg & CSR_GCFG_TIT))
+		return;
+
+	/* Enable guest access to hard timer */
+	write_csr_gcfg(cfg & ~CSR_GCFG_TIT);
+
+	/*
+	 * Freeze the soft-timer and sync the guest stable timer with it. We do
+	 * this with interrupts disabled to avoid latency.
+	 */
+	hrtimer_cancel(&vcpu->arch.swtimer);
+}
+
+/*
+ * Restore soft timer state from saved context.
+ */
+void kvm_restore_timer(struct kvm_vcpu *vcpu)
+{
+	unsigned long cfg, delta, period;
+	ktime_t expire, now;
+	struct loongarch_csrs *csr = vcpu->arch.csr;
+
+	/*
+	 * Set guest stable timer cfg csr
+	 */
+	cfg = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_TCFG);
+	kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_ESTAT);
+	kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_TCFG);
+	if (!(cfg & CSR_TCFG_EN)) {
+		/* Guest timer is disabled, just restore timer registers */
+		kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_TVAL);
+		return;
+	}
+
+	/*
+	 * Set remainder tick value if not expired
+	 */
+	now = ktime_get();
+	expire = vcpu->arch.expire;
+	if (ktime_before(now, expire))
+		delta = ktime_to_tick(vcpu, ktime_sub(expire, now));
+	else {
+		if (cfg & CSR_TCFG_PERIOD) {
+			period = cfg & CSR_TCFG_VAL;
+			delta = ktime_to_tick(vcpu, ktime_sub(now, expire));
+			delta = period - (delta % period);
+		} else
+			delta = 0;
+		/*
+		 * Inject timer here though sw timer should inject timer
+		 * interrupt async already, since sw timer may be cancelled
+		 * during injecting intr async in function kvm_acquire_timer
+		 */
+		kvm_queue_irq(vcpu, INT_TI);
+	}
+
+	write_gcsr_timertick(delta);
+}
+
+/*
+ * Save guest timer state and switch to software emulation of guest
+ * timer. The hard timer must already be in use, so preemption should be
+ * disabled.
+ */
+static void _kvm_save_timer(struct kvm_vcpu *vcpu)
+{
+	unsigned long ticks, delta;
+	ktime_t expire;
+	struct loongarch_csrs *csr = vcpu->arch.csr;
+
+	ticks = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_TVAL);
+	delta = tick_to_ns(vcpu, ticks);
+	expire = ktime_add_ns(ktime_get(), delta);
+	vcpu->arch.expire = expire;
+	if (ticks) {
+		/*
+		 * Update hrtimer to use new timeout
+		 * HRTIMER_MODE_PINNED is suggested since vcpu may run in
+		 * the same physical cpu in next time
+		 */
+		hrtimer_cancel(&vcpu->arch.swtimer);
+		hrtimer_start(&vcpu->arch.swtimer, expire, HRTIMER_MODE_ABS_PINNED);
+	} else
+		/*
+		 * Inject timer interrupt so that hall polling can dectect and exit
+		 */
+		kvm_queue_irq(vcpu, INT_TI);
+}
+
+/*
+ * Save guest timer state and switch to soft guest timer if hard timer was in
+ * use.
+ */
+void kvm_save_timer(struct kvm_vcpu *vcpu)
+{
+	unsigned long cfg;
+	struct loongarch_csrs *csr = vcpu->arch.csr;
+
+	preempt_disable();
+	cfg = read_csr_gcfg();
+	if (!(cfg & CSR_GCFG_TIT)) {
+		/* Disable guest use of hard timer */
+		write_csr_gcfg(cfg | CSR_GCFG_TIT);
+
+		/* Save hard timer state */
+		kvm_save_hw_gcsr(csr, LOONGARCH_CSR_TCFG);
+		kvm_save_hw_gcsr(csr, LOONGARCH_CSR_TVAL);
+		if (kvm_read_sw_gcsr(csr, LOONGARCH_CSR_TCFG) & CSR_TCFG_EN)
+			_kvm_save_timer(vcpu);
+	}
+
+	/* Save timer-related state to vCPU context */
+	kvm_save_hw_gcsr(csr, LOONGARCH_CSR_ESTAT);
+	preempt_enable();
+}
+
+void kvm_reset_timer(struct kvm_vcpu *vcpu)
+{
+	write_gcsr_timercfg(0);
+	kvm_write_sw_gcsr(vcpu->arch.csr, LOONGARCH_CSR_TCFG, 0);
+	hrtimer_cancel(&vcpu->arch.swtimer);
+}