Re: [RFC PATCH v2 10/26] ARM: GICv3: forward pending LPIs to guests

[Stefano Stabellini <sstabellini@kernel.org>]

On Thu, 22 Dec 2016, Andre Przywara wrote:
> Upon receiving an LPI, we need to find the right VCPU and virtual IRQ
> number to get this IRQ injected.
> Iterate our two-level LPI table to find this information quickly when
> the host takes an LPI. Call the existing injection function to let the
> GIC emulation deal with this interrupt.
> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
>  xen/arch/arm/gic-its.c    | 35 +++++++++++++++++++++++++++++++++++
>  xen/arch/arm/gic.c        |  6 ++++--
>  xen/include/asm-arm/irq.h |  8 ++++++++
>  3 files changed, 47 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/arm/gic-its.c b/xen/arch/arm/gic-its.c
> index e7ddd90..0d4ca1b 100644
> --- a/xen/arch/arm/gic-its.c
> +++ b/xen/arch/arm/gic-its.c
> @@ -72,6 +72,41 @@ static union host_lpi *gic_get_host_lpi(uint32_t plpi)
>      return &lpi_data.host_lpis[plpi / HOST_LPIS_PER_PAGE][plpi % HOST_LPIS_PER_PAGE];
>  }
>  
> +/* Handle incoming LPIs, which are a bit special, because they are potentially
> + * numerous and also only get injected into guests. Treat them specially here,
> + * by just looking up their target vCPU and virtual LPI number and hand it
> + * over to the injection function.
> + */
> +void do_LPI(unsigned int lpi)
> +{
> +    struct domain *d;
> +    union host_lpi *hlpip, hlpi;
> +    struct vcpu *vcpu;
> +
> +    WRITE_SYSREG32(lpi, ICC_EOIR1_EL1);
> +
> +    hlpip = gic_get_host_lpi(lpi);
> +    if ( !hlpip )
> +        return;
> +
> +    hlpi.data = hlpip->data;

Why can't we just reference hlpip directly throughout this function? Is
it for atomicity reasons?


> +    /* We may have mapped more host LPIs than the guest actually asked for. */
> +    if ( !hlpi.virt_lpi )
> +        return;
> +
> +    d = get_domain_by_id(hlpi.dom_id);
> +    if ( !d )
> +        return;
> +
> +    if ( hlpi.vcpu_id >= d->max_vcpus )
> +        return;
> +
> +    vcpu = d->vcpu[hlpi.vcpu_id];
> +
> +    vgic_vcpu_inject_irq(vcpu, hlpi.virt_lpi);
> +}
> +
>  #define ITS_CMD_QUEUE_SZ                                SZ_64K
>  
>  static int its_send_command(struct host_its *hw_its, void *its_cmd)
> diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
> index 6f25501..7d428dc 100644
> --- a/xen/arch/arm/gic.c
> +++ b/xen/arch/arm/gic.c
> @@ -700,8 +700,10 @@ void gic_interrupt(struct cpu_user_regs *regs, int is_fiq)
>              local_irq_enable();
>              do_IRQ(regs, irq, is_fiq);
>              local_irq_disable();
> -        }
> -        else if (unlikely(irq < 16))
> +        } else if ( irq >= 8192 )
> +        {
> +            do_LPI(irq);
> +        } else if ( unlikely(irq < 16) )
>          {
>              do_sgi(regs, irq);
>          }
> diff --git a/xen/include/asm-arm/irq.h b/xen/include/asm-arm/irq.h
> index 8f7a167..ee47de8 100644
> --- a/xen/include/asm-arm/irq.h
> +++ b/xen/include/asm-arm/irq.h
> @@ -34,6 +34,14 @@ struct irq_desc *__irq_to_desc(int irq);
>  
>  void do_IRQ(struct cpu_user_regs *regs, unsigned int irq, int is_fiq);
>  
> +#ifdef CONFIG_HAS_ITS
> +void do_LPI(unsigned int irq);
> +#else
> +static inline void do_LPI(unsigned int irq)
> +{
> +}
> +#endif
> +
>  #define domain_pirq_to_irq(d, pirq) (pirq)
>  
>  bool_t is_assignable_irq(unsigned int irq);
> -- 
> 2.9.0
> 

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