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

[Anup Patel]

On Wed, Feb 8, 2023 at 5:45 AM Atish Patra <atishp@xxxxxxxxxxxxxx> wrote:
>
> 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.

This is for CPU hotplug where the VM/VCPU are not
destroyed but the host CPU is going down so we need
to cleanup sleeping VCPUs.

Regards,
Anup

>
> > +       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