Re: [Xen-devel] [PATCH v4 27/27] ARM: vGIC: advertise LPI support

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

Sounds like I missed this patch. We spoke about it f2f today, I will 
comments here for recording purpose.
On 03/04/17 21:28, Andre Przywara wrote:
> To let a guest know about the availability of virtual LPIs, set the
> respective bits in the virtual GIC registers and let a guest control
> the LPI enable bit.
> Only report the LPI capability if the host has initialized at least
> one ITS.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> ---
>  xen/arch/arm/vgic-v3.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 69 insertions(+), 5 deletions(-)
>
> diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
> index 3fc309e..a6a0126 100644
> --- a/xen/arch/arm/vgic-v3.c
> +++ b/xen/arch/arm/vgic-v3.c
> @@ -168,8 +168,10 @@ static int __vgic_v3_rdistr_rd_mmio_read(struct vcpu *v, 
> mmio_info_t *info,
>      switch ( gicr_reg )
>      {
>      case VREG32(GICR_CTLR):
> -        /* We have not implemented LPI's, read zero */
> -        goto read_as_zero_32;
> +        if ( dabt.size != DABT_WORD ) goto bad_width;
> +        *r = vgic_reg32_extract(!!(v->arch.vgic.flags & VGIC_V3_LPIS_ENABLED),
> +                                info);
It would be clearer to use a temporary variable here.

> +        return 1;
>
>      case VREG32(GICR_IIDR):
>          if ( dabt.size != DABT_WORD ) goto bad_width;
> @@ -181,16 +183,19 @@ static int __vgic_v3_rdistr_rd_mmio_read(struct vcpu *v, 
> mmio_info_t *info,
>          uint64_t typer, aff;
>
>          if ( !vgic_reg64_check_access(dabt) ) goto bad_width;
> -        /* TBD: Update processor id in [23:8] when ITS support is added */
>          aff = (MPIDR_AFFINITY_LEVEL(v->arch.vmpidr, 3) << 56 |
>                 MPIDR_AFFINITY_LEVEL(v->arch.vmpidr, 2) << 48 |
>                 MPIDR_AFFINITY_LEVEL(v->arch.vmpidr, 1) << 40 |
>                 MPIDR_AFFINITY_LEVEL(v->arch.vmpidr, 0) << 32);
>          typer = aff;
> +        typer |= (v->vcpu_id & 0xffff) << 8;
Please document in the code why you added that.

>          if ( v->arch.vgic.flags & VGIC_V3_RDIST_LAST )
>              typer |= GICR_TYPER_LAST;
>
> +        if ( v->domain->arch.vgic.has_its )
> +            typer |= GICR_TYPER_PLPIS;
> +
>          *r = vgic_reg64_extract(typer, info);
>
>          return 1;
> @@ -433,6 +438,35 @@ static uint64_t sanitize_pendbaser(uint64_t reg)
>      return reg;
>  }
>
> +static void vgic_vcpu_enable_lpis(struct vcpu *v)
> +{
> +    uint64_t reg = v->domain->arch.vgic.rdist_propbase;
> +    unsigned int nr_lpis = BIT((reg & 0x1f) + 1) - LPI_OFFSET;
> +    int nr_pages;
> +
> +    /* The first VCPU to enable LPIs maps the property table. */
> +    if ( !v->domain->arch.vgic.nr_lpis )
> +    {
> +        v->domain->arch.vgic.nr_lpis = nr_lpis;
> +
> +        nr_pages = DIV_ROUND_UP(nr_lpis, PAGE_SIZE);
> +        get_guest_pages(v->domain, reg & GENMASK_ULL(51, 12), nr_pages);
> +        gprintk(XENLOG_INFO, "VGIC-v3: VCPU%d mapped %d pages for property 
> table\n",
> +               v->vcpu_id, nr_pages);
> +    }
> +    nr_pages = DIV_ROUND_UP(((nr_lpis + LPI_OFFSET) / 8), PAGE_SIZE);
> +    reg = v->arch.vgic.rdist_pendbase;
> +
> +    get_guest_pages(v->domain, reg & GENMASK_ULL(51, 12), nr_pages);
> +
> +    gprintk(XENLOG_INFO, "VGIC-v3: VCPU%d mapped %d pages for pending table\n",
> +            v->vcpu_id, nr_pages);
> +
> +    v->arch.vgic.flags |= VGIC_V3_LPIS_ENABLED;
> +
> +    printk("VGICv3: enabled %d LPIs for VCPU%d\n", nr_lpis, v->vcpu_id);
> +}
> +
>  static int __vgic_v3_rdistr_rd_mmio_write(struct vcpu *v, mmio_info_t *info,
>                                            uint32_t gicr_reg,
>                                            register_t r)
> @@ -443,8 +477,18 @@ static int __vgic_v3_rdistr_rd_mmio_write(struct vcpu *v, 
> mmio_info_t *info,
>      switch ( gicr_reg )
>      {
>      case VREG32(GICR_CTLR):
> -        /* LPI's not implemented */
> -        goto write_ignore_32;
> +        if ( dabt.size != DABT_WORD ) goto bad_width;
> +        if ( !v->domain->arch.vgic.has_its )
> +            return 1;
> +
> +        /* LPIs can only be enabled once, but never disabled again. */
> +        if ( !(r & GICR_CTLR_ENABLE_LPIS) ||
> +             (v->arch.vgic.flags & VGIC_V3_LPIS_ENABLED) )
> +            return 1;
This likely needs some locking.

> +
> +        vgic_vcpu_enable_lpis(v);
> +
> +        return 1;
>
>      case VREG32(GICR_IIDR):
>          /* RO */
> @@ -1044,6 +1088,11 @@ static int vgic_v3_distr_mmio_read(struct vcpu *v, 
> mmio_info_t *info,
>          typer = ((ncpus - 1) << GICD_TYPE_CPUS_SHIFT |
>                   DIV_ROUND_UP(v->domain->arch.vgic.nr_spis, 32));
>
> +        if ( v->domain->arch.vgic.has_its )
> +        {
> +            typer |= GICD_TYPE_LPIS;
> +            irq_bits = 16;
Why 16? Likely, this will be based on the configuration of the guest.

> +        }
>          typer |= (irq_bits - 1) << GICD_TYPE_ID_BITS_SHIFT;
>
>          *r = vgic_reg32_extract(typer, info);
> @@ -1665,6 +1714,21 @@ static int vgic_v3_domain_init(struct domain *d)
>
>  static void vgic_v3_domain_free(struct domain *d)
>  {
> +    int nr_pages;
> +    struct vcpu *v;
> +
> +    if ( d->arch.vgic.nr_lpis )
> +    {
> +        nr_pages = DIV_ROUND_UP(d->arch.vgic.nr_lpis, PAGE_SIZE);
> +        put_guest_pages(d, d->arch.vgic.rdist_propbase & GENMASK_ULL(51, 12),
> +                        nr_pages);
> +
> +        nr_pages = DIV_ROUND_UP((d->arch.vgic.nr_lpis + LPI_OFFSET) / 8,
> +                                PAGE_SIZE);
> +        for_each_vcpu(d, v)
> +            put_guest_pages(d, v->arch.vgic.rdist_pendbase & GENMASK_ULL(51, 
> 12),
> +                            nr_pages);
> +    }
>      gicv3_its_unmap_all_devices(d);
>      radix_tree_destroy(&d->arch.vgic.pend_lpi_tree, NULL);
>      xfree(d->arch.vgic.rdist_regions);
Cheers,

--
Julien Grall

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