Re: [PATCH v2 7/7] RISC-V: KVM: Implement guest external interrupt line management

[Atish Patra]

On Fri, Jan 27, 2023 at 11:28 PM Anup Patel <apatel@xxxxxxxxxxxxxxxx> wrote:
>
> The RISC-V host will have one guest external interrupt line for each
> VS-level IMSICs associated with a HART. The guest external interrupt
> lines are per-HART resources and hypervisor can use HGEIE, HGEIP, and
> HIE CSRs to manage these guest external interrupt lines.
>
> Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> ---
>  arch/riscv/include/asm/kvm_aia.h |  10 ++
>  arch/riscv/kvm/aia.c             | 241 +++++++++++++++++++++++++++++++
>  arch/riscv/kvm/main.c            |   3 +-
>  arch/riscv/kvm/vcpu.c            |   2 +
>  4 files changed, 255 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/include/asm/kvm_aia.h b/arch/riscv/include/asm/kvm_aia.h
> index 1de0717112e5..0938e0cadf80 100644
> --- a/arch/riscv/include/asm/kvm_aia.h
> +++ b/arch/riscv/include/asm/kvm_aia.h
> @@ -44,10 +44,15 @@ struct kvm_vcpu_aia {
>
>  #define irqchip_in_kernel(k)           ((k)->arch.aia.in_kernel)
>
> +extern unsigned int kvm_riscv_aia_nr_hgei;
>  DECLARE_STATIC_KEY_FALSE(kvm_riscv_aia_available);
>  #define kvm_riscv_aia_available() \
>         static_branch_unlikely(&kvm_riscv_aia_available)
>
> +static inline void kvm_riscv_vcpu_aia_imsic_release(struct kvm_vcpu *vcpu)
> +{
> +}
> +
>  #define KVM_RISCV_AIA_IMSIC_TOPEI      (ISELECT_MASK + 1)
>  static inline int kvm_riscv_vcpu_aia_imsic_rmw(struct kvm_vcpu *vcpu,
>                                                unsigned long isel,
> @@ -119,6 +124,11 @@ static inline void kvm_riscv_aia_destroy_vm(struct kvm *kvm)
>  {
>  }
>
> +int kvm_riscv_aia_alloc_hgei(int cpu, struct kvm_vcpu *owner,
> +                            void __iomem **hgei_va, phys_addr_t *hgei_pa);
> +void kvm_riscv_aia_free_hgei(int cpu, int hgei);
> +void kvm_riscv_aia_wakeon_hgei(struct kvm_vcpu *owner, bool enable);
> +
>  void kvm_riscv_aia_enable(void);
>  void kvm_riscv_aia_disable(void);
>  int kvm_riscv_aia_init(void);
> diff --git a/arch/riscv/kvm/aia.c b/arch/riscv/kvm/aia.c
> index 3d68189e0bb1..f375069fdaf4 100644
> --- a/arch/riscv/kvm/aia.c
> +++ b/arch/riscv/kvm/aia.c
> @@ -7,11 +7,46 @@
>   *     Anup Patel <apatel@xxxxxxxxxxxxxxxx>
>   */
>
> +#include <linux/bitops.h>
> +#include <linux/irq.h>
> +#include <linux/irqdomain.h>
>  #include <linux/kvm_host.h>
> +#include <linux/percpu.h>
> +#include <linux/spinlock.h>
>  #include <asm/hwcap.h>
>
> +struct aia_hgei_control {
> +       raw_spinlock_t lock;
> +       unsigned long free_bitmap;
> +       struct kvm_vcpu *owners[BITS_PER_LONG];
> +};
> +static DEFINE_PER_CPU(struct aia_hgei_control, aia_hgei);
> +static int hgei_parent_irq;
> +
> +unsigned int kvm_riscv_aia_nr_hgei;
>  DEFINE_STATIC_KEY_FALSE(kvm_riscv_aia_available);
>
> +static int aia_find_hgei(struct kvm_vcpu *owner)
> +{
> +       int i, hgei;
> +       unsigned long flags;
> +       struct aia_hgei_control *hgctrl = this_cpu_ptr(&aia_hgei);
> +
> +       raw_spin_lock_irqsave(&hgctrl->lock, flags);
> +
> +       hgei = -1;
> +       for (i = 1; i <= kvm_riscv_aia_nr_hgei; i++) {
> +               if (hgctrl->owners[i] == owner) {
> +                       hgei = i;
> +                       break;
> +               }
> +       }
> +
> +       raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
> +
> +       return hgei;
> +}
> +
>  static void aia_set_hvictl(bool ext_irq_pending)
>  {
>         unsigned long hvictl;
> @@ -55,6 +90,7 @@ void kvm_riscv_vcpu_aia_sync_interrupts(struct kvm_vcpu *vcpu)
>
>  bool kvm_riscv_vcpu_aia_has_interrupts(struct kvm_vcpu *vcpu, u64 mask)
>  {
> +       int hgei;
>         unsigned long seip;
>
>         if (!kvm_riscv_aia_available())
> @@ -72,6 +108,10 @@ bool kvm_riscv_vcpu_aia_has_interrupts(struct kvm_vcpu *vcpu, u64 mask)
>         if (!kvm_riscv_aia_initialized(vcpu->kvm) || !seip)
>                 return false;
>
> +       hgei = aia_find_hgei(vcpu);
> +       if (hgei > 0)
> +               return (csr_read(CSR_HGEIP) & BIT(hgei)) ? true : false;
> +
>         return false;
>  }
>
> @@ -343,6 +383,144 @@ int kvm_riscv_vcpu_aia_rmw_ireg(struct kvm_vcpu *vcpu, unsigned int csr_num,
>         return KVM_INSN_EXIT_TO_USER_SPACE;
>  }
>
> +int kvm_riscv_aia_alloc_hgei(int cpu, struct kvm_vcpu *owner,
> +                            void __iomem **hgei_va, phys_addr_t *hgei_pa)
> +{
> +       int ret = -ENOENT;
> +       unsigned long flags;
> +       struct aia_hgei_control *hgctrl = per_cpu_ptr(&aia_hgei, cpu);
> +
> +       if (!kvm_riscv_aia_available())
> +               return -ENODEV;
> +       if (!hgctrl)
> +               return -ENODEV;
> +
> +       raw_spin_lock_irqsave(&hgctrl->lock, flags);
> +
> +       if (hgctrl->free_bitmap) {
> +               ret = __ffs(hgctrl->free_bitmap);
> +               hgctrl->free_bitmap &= ~BIT(ret);
> +               hgctrl->owners[ret] = owner;
> +       }
> +
> +       raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
> +
> +       /* TODO: To be updated later by AIA in-kernel irqchip support */
> +       if (hgei_va)
> +               *hgei_va = NULL;
> +       if (hgei_pa)
> +               *hgei_pa = 0;
> +
> +       return ret;
> +}
> +
> +void kvm_riscv_aia_free_hgei(int cpu, int hgei)
> +{
> +       unsigned long flags;
> +       struct aia_hgei_control *hgctrl = per_cpu_ptr(&aia_hgei, cpu);
> +
> +       if (!kvm_riscv_aia_available() || !hgctrl)
> +               return;
> +
> +       raw_spin_lock_irqsave(&hgctrl->lock, flags);
> +
> +       if (hgei > 0 && hgei <= kvm_riscv_aia_nr_hgei) {
> +               if (!(hgctrl->free_bitmap & BIT(hgei))) {
> +                       hgctrl->free_bitmap |= BIT(hgei);
> +                       hgctrl->owners[hgei] = NULL;
> +               }
> +       }
> +
> +       raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
> +}
> +
> +void kvm_riscv_aia_wakeon_hgei(struct kvm_vcpu *owner, bool enable)
> +{
> +       int hgei;
> +
> +       if (!kvm_riscv_aia_available())
> +               return;
> +
> +       hgei = aia_find_hgei(owner);
> +       if (hgei > 0) {
> +               if (enable)
> +                       csr_set(CSR_HGEIE, BIT(hgei));
> +               else
> +                       csr_clear(CSR_HGEIE, BIT(hgei));
> +       }
> +}
> +
> +static irqreturn_t hgei_interrupt(int irq, void *dev_id)
> +{
> +       int i;
> +       unsigned long hgei_mask, flags;
> +       struct aia_hgei_control *hgctrl = this_cpu_ptr(&aia_hgei);
> +
> +       hgei_mask = csr_read(CSR_HGEIP) & csr_read(CSR_HGEIE);
> +       csr_clear(CSR_HGEIE, hgei_mask);
> +
> +       raw_spin_lock_irqsave(&hgctrl->lock, flags);
> +
> +       for_each_set_bit(i, &hgei_mask, BITS_PER_LONG) {
> +               if (hgctrl->owners[i])
> +                       kvm_vcpu_kick(hgctrl->owners[i]);
> +       }
> +
> +       raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
> +
> +       return IRQ_HANDLED;
> +}
> +
> +static int aia_hgei_init(void)
> +{
> +       int cpu, rc;
> +       struct irq_domain *domain;
> +       struct aia_hgei_control *hgctrl;
> +
> +       /* Initialize per-CPU guest external interrupt line management */
> +       for_each_possible_cpu(cpu) {
> +               hgctrl = per_cpu_ptr(&aia_hgei, cpu);
> +               raw_spin_lock_init(&hgctrl->lock);
> +               if (kvm_riscv_aia_nr_hgei) {
> +                       hgctrl->free_bitmap =
> +                               BIT(kvm_riscv_aia_nr_hgei + 1) - 1;
> +                       hgctrl->free_bitmap &= ~BIT(0);
> +               } else
> +                       hgctrl->free_bitmap = 0;
> +       }
> +
> +       /* Find INTC irq domain */
> +       domain = irq_find_matching_fwnode(riscv_get_intc_hwnode(),
> +                                         DOMAIN_BUS_ANY);
> +       if (!domain) {
> +               kvm_err("unable to find INTC domain\n");
> +               return -ENOENT;
> +       }
> +
> +       /* Map per-CPU SGEI interrupt from INTC domain */
> +       hgei_parent_irq = irq_create_mapping(domain, IRQ_S_GEXT);
> +       if (!hgei_parent_irq) {
> +               kvm_err("unable to map SGEI IRQ\n");
> +               return -ENOMEM;
> +       }
> +
> +       /* Request per-CPU SGEI interrupt */
> +       rc = request_percpu_irq(hgei_parent_irq, hgei_interrupt,
> +                               "riscv-kvm", &aia_hgei);
> +       if (rc) {
> +               kvm_err("failed to request SGEI IRQ\n");
> +               return rc;
> +       }
> +
> +       return 0;
> +}
> +
> +static void aia_hgei_exit(void)
> +{
> +       /* Free per-CPU SGEI interrupt */
> +       free_percpu_irq(hgei_parent_irq, &aia_hgei);
> +}
> +
>  void kvm_riscv_aia_enable(void)
>  {
>         if (!kvm_riscv_aia_available())
> @@ -357,21 +535,79 @@ void kvm_riscv_aia_enable(void)
>         csr_write(CSR_HVIPRIO1H, 0x0);
>         csr_write(CSR_HVIPRIO2H, 0x0);
>  #endif
> +
> +       /* Enable per-CPU SGEI interrupt */
> +       enable_percpu_irq(hgei_parent_irq,
> +                         irq_get_trigger_type(hgei_parent_irq));
> +       csr_set(CSR_HIE, BIT(IRQ_S_GEXT));
>  }
>
>  void kvm_riscv_aia_disable(void)
>  {
> +       int i;
> +       unsigned long flags;
> +       struct kvm_vcpu *vcpu;
> +       struct aia_hgei_control *hgctrl = this_cpu_ptr(&aia_hgei);
> +
>         if (!kvm_riscv_aia_available())
>                 return;
>
> +       /* Disable per-CPU SGEI interrupt */
> +       csr_clear(CSR_HIE, BIT(IRQ_S_GEXT));
> +       disable_percpu_irq(hgei_parent_irq);
> +
>         aia_set_hvictl(false);
> +
> +       raw_spin_lock_irqsave(&hgctrl->lock, flags);
> +
> +       for (i = 0; i <= kvm_riscv_aia_nr_hgei; i++) {
> +               vcpu = hgctrl->owners[i];
> +               if (!vcpu)
> +                       continue;
> +
> +               /*
> +                * We release hgctrl->lock before notifying IMSIC
> +                * so that we don't have lock ordering issues.
> +                */
> +               raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
> +
> +               /* Notify IMSIC */
> +               kvm_riscv_vcpu_aia_imsic_release(vcpu);
> +
> +               /*
> +                * Wakeup VCPU if it was blocked so that it can
> +                * run on other HARTs
> +                */
> +               if (csr_read(CSR_HGEIE) & BIT(i)) {
> +                       csr_clear(CSR_HGEIE, BIT(i));
> +                       kvm_vcpu_kick(vcpu);
> +               }
> +
> +               raw_spin_lock_irqsave(&hgctrl->lock, flags);
> +       }
> +

We shouldn't access vcpu related data here as
kvm_arch_destroy_vm/kvm_destroy_vcpus
is called before hardware_disable_all is invoked.

> +       raw_spin_unlock_irqrestore(&hgctrl->lock, flags);
>  }
>
>  int kvm_riscv_aia_init(void)
>  {
> +       int rc;
> +
>         if (!riscv_isa_extension_available(NULL, SxAIA))
>                 return -ENODEV;
>
> +       /* Figure-out number of bits in HGEIE */
> +       csr_write(CSR_HGEIE, -1UL);
> +       kvm_riscv_aia_nr_hgei = fls_long(csr_read(CSR_HGEIE));
> +       csr_write(CSR_HGEIE, 0);
> +       if (kvm_riscv_aia_nr_hgei)
> +               kvm_riscv_aia_nr_hgei--;
> +
> +       /* Initialize guest external interrupt line management */
> +       rc = aia_hgei_init();
> +       if (rc)
> +               return rc;
> +
>         /* Enable KVM AIA support */
>         static_branch_enable(&kvm_riscv_aia_available);
>
> @@ -380,4 +616,9 @@ int kvm_riscv_aia_init(void)
>
>  void kvm_riscv_aia_exit(void)
>  {
> +       if (!kvm_riscv_aia_available())
> +               return;
> +
> +       /* Cleanup the HGEI state */
> +       aia_hgei_exit();
>  }
> diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
> index d8ff44eb04ca..5cf37dbe8a38 100644
> --- a/arch/riscv/kvm/main.c
> +++ b/arch/riscv/kvm/main.c
> @@ -125,7 +125,8 @@ int kvm_arch_init(void *opaque)
>         kvm_info("VMID %ld bits available\n", kvm_riscv_gstage_vmid_bits());
>
>         if (kvm_riscv_aia_available())
> -               kvm_info("AIA available\n");
> +               kvm_info("AIA available with %d guest external interrupts\n",
> +                        kvm_riscv_aia_nr_hgei);
>
>         return 0;
>  }
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 151b35b3b05f..1daa1936b642 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -240,10 +240,12 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
>
>  void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)
>  {
> +       kvm_riscv_aia_wakeon_hgei(vcpu, true);
>  }
>
>  void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu)
>  {
> +       kvm_riscv_aia_wakeon_hgei(vcpu, false);
>  }
>
>  int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
> --
> 2.34.1
>


-- 
Regards,
Atish