Re: [PATCH 1/2] arm: vgic: Add the ability to trigger MSIs from the Hypervisor

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Sun, 14 Jan 2024, Mykyta Poturai wrote:
> Add the vgic_its_trigger_msi() function to the vgic interface. This
> function allows to inject MSIs from the Hypervisor to the guest.
> Which is useful for userspace PCI backend drivers.
> 
> Signed-off-by: Mykyta Poturai <mykyta_poturai@xxxxxxxx>
> ---
>  xen/arch/arm/include/asm/vgic.h | 11 +++++++++++
>  xen/arch/arm/vgic-v3-its.c      | 35 +++++++++++++++++++++++++++++++++
>  2 files changed, 46 insertions(+)
> 
> diff --git a/xen/arch/arm/include/asm/vgic.h b/xen/arch/arm/include/asm/vgic.h
> index 922779ce14..4695743848 100644
> --- a/xen/arch/arm/include/asm/vgic.h
> +++ b/xen/arch/arm/include/asm/vgic.h
> @@ -317,6 +317,17 @@ extern bool vgic_migrate_irq(struct vcpu *old, struct 
> vcpu *new, unsigned int ir
>  extern void vgic_check_inflight_irqs_pending(struct domain *d, struct vcpu 
> *v,
>                                               unsigned int rank, uint32_t r);
>  
> +#ifdef CONFIG_HAS_ITS
> +int vgic_its_trigger_msi(struct domain *d, paddr_t doorbell_address,
> +                                u32 devid, u32 eventid);
> +#else
> +static inline int vgic_its_trigger_msi(struct domain *d, paddr_t 
> doorbell_address,
> +                                u32 devid, u32 eventid)
> +{
> +    return -EOPNOTSUPP;
> +}
> +#endif /* CONFIG_HAS_ITS */
> +
>  #endif /* !CONFIG_NEW_VGIC */
>  
>  /*** Common VGIC functions used by Xen arch code ****/
> diff --git a/xen/arch/arm/vgic-v3-its.c b/xen/arch/arm/vgic-v3-its.c
> index 70b5aeb822..683a378f6e 100644
> --- a/xen/arch/arm/vgic-v3-its.c
> +++ b/xen/arch/arm/vgic-v3-its.c
> @@ -1484,6 +1484,41 @@ static int vgic_v3_its_init_virtual(struct domain *d, 
> paddr_t guest_addr,
>      return 0;
>  }
>  
> +int vgic_its_trigger_msi(struct domain *d, paddr_t doorbell_address,
> +                                u32 devid, u32 eventid)
> +{
> +    struct vcpu *vcpu;
> +    struct virt_its *pos, *temp;
> +    struct virt_its *its = NULL;
> +    uint32_t vlpi;
> +    bool ret;
> +
> +    list_for_each_entry_safe( pos, temp, &d->arch.vgic.vits_list, vits_list )
> +    {
> +        if ( pos->doorbell_address == doorbell_address )
> +        {
> +            its = pos;
> +            break;
> +        }
> +    }
> +
> +    if ( !its )
> +        return -EINVAL;
> +
> +    spin_lock(&its->its_lock);
> +    ret = read_itte(its, devid, eventid, &vcpu, &vlpi);
> +    spin_unlock(&its->its_lock);
> +    if ( !ret )
> +        return -1;
> +
> +    if ( vlpi == INVALID_LPI )
> +        return -1;

We need a better error code, maybe EINVAL or ENOENT ?

Other than that, it looks OK


> +    vgic_vcpu_inject_lpi(its->d, vlpi);
> +
> +    return 0;
> +}
> +
>  unsigned int vgic_v3_its_count(const struct domain *d)
>  {
>      struct host_its *hw_its;
> -- 
> 2.34.1
>