Re: [Xen-devel] [PATCH v2 13/27] ARM: vGICv3: Handle disabled LPIs

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 03/16/2017 11:20 AM, Andre Przywara wrote:
> If a guest disables an LPI, we do not forward this to the associated
> host LPI to avoid queueing commands to the host ITS command queue.
> So it may happen that an LPI fires nevertheless on the host. In this
> case we can bail out early, but have to save the pending state on the
> virtual side.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
Please see alpine.DEB.2.10.1701051422020.2866@sstabellini-ThinkPad-X260

> ---
>  xen/arch/arm/gic-v3-lpi.c  |  8 ++++++++
>  xen/arch/arm/vgic-v3.c     | 12 ++++++++++++
>  xen/include/asm-arm/vgic.h |  6 ++++++
>  3 files changed, 26 insertions(+)
>
> diff --git a/xen/arch/arm/gic-v3-lpi.c b/xen/arch/arm/gic-v3-lpi.c
> index 0579976..994698e 100644
> --- a/xen/arch/arm/gic-v3-lpi.c
> +++ b/xen/arch/arm/gic-v3-lpi.c
> @@ -142,6 +142,14 @@ void do_LPI(unsigned int lpi)
>
>      put_domain(d);
>
> +    /*
> +     * We keep all host LPIs enabled, so check if it's disabled on the guest
> +     * side and just record this LPI in the virtual pending table in this case.
> +     * The guest picks it up once it gets enabled again.
> +     */
> +    if ( !vgic_can_inject_lpi(vcpu, hlpi.virt_lpi) )
> +        return;
> +
>      vgic_vcpu_inject_irq(vcpu, hlpi.virt_lpi);
>  }
>
> diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
> index c6db2d7..de625bf 100644
> --- a/xen/arch/arm/vgic-v3.c
> +++ b/xen/arch/arm/vgic-v3.c
> @@ -498,6 +498,18 @@ bool vgic_lpi_is_enabled(struct domain *d, uint32_t vlpi)
>      return d->arch.vgic.proptable[vlpi - LPI_OFFSET] & LPI_PROP_ENABLED;
>  }
>
> +bool vgic_can_inject_lpi(struct vcpu *vcpu, uint32_t vlpi)
> +{
> +    if ( vlpi >= vcpu->domain->arch.vgic.nr_lpis )
> +        return false;
> +
> +    if ( vgic_lpi_is_enabled(vcpu->domain, vlpi) )
> +        return true;
> +
> +    set_bit(vlpi - LPI_OFFSET, vcpu->arch.vgic.pendtable);
New line here.

> +    return false;
> +}
> +
>  static int __vgic_v3_rdistr_rd_mmio_write(struct vcpu *v, mmio_info_t *info,
>                                            uint32_t gicr_reg,
>                                            register_t r)
> diff --git a/xen/include/asm-arm/vgic.h b/xen/include/asm-arm/vgic.h
> index f8bccfa..302702e 100644
> --- a/xen/include/asm-arm/vgic.h
> +++ b/xen/include/asm-arm/vgic.h
> @@ -323,6 +323,7 @@ int vgic_v3_init(struct domain *d, int *mmio_count);
>  #ifdef CONFIG_HAS_GICV3
>  extern int vgic_lpi_get_priority(struct domain *d, uint32_t vlpi);
>  extern bool vgic_lpi_is_enabled(struct domain *d, uint32_t vlpi);
> +extern bool vgic_can_inject_lpi(struct vcpu *v, uint32_t vlpi);
>  #else
>  static inline int vgic_lpi_get_priority(struct domain *d, uint32_t vlpi)
>  {
> @@ -333,6 +334,11 @@ static inline bool vgic_lpi_is_enabled(struct domain *d, 
> uint32_t vlpi)
>  {
>      return false;
>  }
> +
> +static inline bool vgic_can_inject_lpi(struct vcpu *v, uint32_t vlpi)
> +{
> +    return false;
> +}
Why do you need this dummy helper?

>  #endif
>
>  extern int domain_vgic_register(struct domain *d, int *mmio_count);
Regards,

--
Julien Grall

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