Re: [PATCH v18 02/18] RISC-V: Add initial skeletal KVM support

Dan Carpenter
2021-05-19T09:25:34Z

On Wed, May 19, 2021 at 09:05:37AM +0530, Anup Patel wrote:
> +int kvm_arch_hardware_enable(void)
> +{
> + unsigned long hideleg, hedeleg;
> +
> + hedeleg = 0;
> + hedeleg |= (1UL << EXC_INST_MISALIGNED);

You may as well use BIT_UL(EXC_INST_MISALIGNED) for all of these.
There is a Coccinelle script to convert these so please just make it
standard like everyone else.

> + hedeleg |= (1UL << EXC_BREAKPOINT);
> + hedeleg |= (1UL << EXC_SYSCALL);
> + hedeleg |= (1UL << EXC_INST_PAGE_FAULT);
> + hedeleg |= (1UL << EXC_LOAD_PAGE_FAULT);
> + hedeleg |= (1UL << EXC_STORE_PAGE_FAULT);
> + csr_write(CSR_HEDELEG, hedeleg);
> +
> + hideleg = 0;
> + hideleg |= (1UL << IRQ_VS_SOFT);
> + hideleg |= (1UL << IRQ_VS_TIMER);
> + hideleg |= (1UL << IRQ_VS_EXT);
> + csr_write(CSR_HIDELEG, hideleg);
> +
> + csr_write(CSR_HCOUNTEREN, -1UL);
> +
> + csr_write(CSR_HVIP, 0);
> +
> + return 0;
> +}
> +
> +void kvm_arch_hardware_disable(void)
> +{
> + csr_write(CSR_HEDELEG, 0);
> + csr_write(CSR_HIDELEG, 0);
> +}
> +
> +int kvm_arch_init(void *opaque)
> +{
> + if (!riscv_isa_extension_available(NULL, h)) {
> + kvm_info("hypervisor extension not available\n");
> + return -ENODEV;
> + }
> +
> + if (sbi_spec_is_0_1()) {
> + kvm_info("require SBI v0.2 or higher\n");
> + return -ENODEV;
> + }
> +
> + if (sbi_probe_extension(SBI_EXT_RFENCE) <= 0) {

sbi_probe_extension() never returns zero.

> + kvm_info("require SBI RFENCE extension\n");
> + return -ENODEV;
> + }
> +
> + kvm_info("hypervisor extension available\n");
> +
> + return 0;
> +}
> +
> +void kvm_arch_exit(void)
> +{
> +}
> +
> +static int riscv_kvm_init(void)
> +{
> + return kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE);
> +}
> +module_init(riscv_kvm_init);

[ snip ]

> +int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> +{
> + int ret;
> + struct kvm_cpu_trap trap;
> + struct kvm_run *run = vcpu->run;
> +
> + vcpu->arch.srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> +
> + /* Process MMIO value returned from user-space */
> + if (run->exit_reason == KVM_EXIT_MMIO) {
> + ret = kvm_riscv_vcpu_mmio_return(vcpu, vcpu->run);
> + if (ret) {
> + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->arch.srcu_idx);
> + return ret;
> + }
> + }
> +
> + if (run->immediate_exit) {
> + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->arch.srcu_idx);
> + return -EINTR;
> + }
> +
> + vcpu_load(vcpu);
> +
> + kvm_sigset_activate(vcpu);
> +
> + ret = 1;
> + run->exit_reason = KVM_EXIT_UNKNOWN;
> + while (ret > 0) {
> + /* Check conditions before entering the guest */
> + cond_resched();
> +
> + kvm_riscv_check_vcpu_requests(vcpu);
> +
> + preempt_disable();
> +
> + local_irq_disable();
> +
> + /*
> + * Exit if we have a signal pending so that we can deliver
> + * the signal to user space.
> + */
> + if (signal_pending(current)) {
> + ret = -EINTR;
> + run->exit_reason = KVM_EXIT_INTR;
> + }
> +
> + /*
> + * Ensure we set mode to IN_GUEST_MODE after we disable
> + * interrupts and before the final VCPU requests check.
> + * See the comment in kvm_vcpu_exiting_guest_mode() and
> + * Documentation/virtual/kvm/vcpu-requests.rst
> + */
> + vcpu->mode = IN_GUEST_MODE;
> +
> + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->arch.srcu_idx);
> + smp_mb__after_srcu_read_unlock();
> +
> + if (ret <= 0 ||

ret can never be == 0 at this point.

> + kvm_request_pending(vcpu)) {
> + vcpu->mode = OUTSIDE_GUEST_MODE;
> + local_irq_enable();
> + preempt_enable();
> + vcpu->arch.srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + continue;
> + }
> +
> + guest_enter_irqoff();
> +
> + __kvm_riscv_switch_to(&vcpu->arch);
> +
> + vcpu->mode = OUTSIDE_GUEST_MODE;
> + vcpu->stat.exits++;
> +
> + /*
> + * Save SCAUSE, STVAL, HTVAL, and HTINST because we might
> + * get an interrupt between __kvm_riscv_switch_to() and
> + * local_irq_enable() which can potentially change CSRs.
> + */
> + trap.sepc = 0;
> + trap.scause = csr_read(CSR_SCAUSE);
> + trap.stval = csr_read(CSR_STVAL);
> + trap.htval = csr_read(CSR_HTVAL);
> + trap.htinst = csr_read(CSR_HTINST);
> +
> + /*
> + * We may have taken a host interrupt in VS/VU-mode (i.e.
> + * while executing the guest). This interrupt is still
> + * pending, as we haven't serviced it yet!
> + *
> + * We're now back in HS-mode with interrupts disabled
> + * so enabling the interrupts now will have the effect
> + * of taking the interrupt again, in HS-mode this time.
> + */
> + local_irq_enable();
> +
> + /*
> + * We do local_irq_enable() before calling guest_exit() so
> + * that if a timer interrupt hits while running the guest
> + * we account that tick as being spent in the guest. We
> + * enable preemption after calling guest_exit() so that if
> + * we get preempted we make sure ticks after that is not
> + * counted as guest time.
> + */
> + guest_exit();
> +
> + preempt_enable();
> +
> + vcpu->arch.srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> +
> + ret = kvm_riscv_vcpu_exit(vcpu, run, &trap);
> + }
> +
> + kvm_sigset_deactivate(vcpu);
> +
> + vcpu_put(vcpu);
> +
> + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->arch.srcu_idx);
> +
> + return ret;
> +}

regards,
dan carpenter