Re: [Xen-devel] [RFC 2/2] xen/arm: vgic-v3: Support 32-bit access for 64-bit registers

[Vijay Kilari <vijay.kilari@xxxxxxxxx>]

On Tue, Aug 4, 2015 at 5:29 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> Based on 8.1.3 (IHI 0069A), unless stated otherwise, the 64-bit registers
> supports both 32-bit and 64-bits access.
>
> All the registers we properly emulate (i.e not RAZ/WI) supports 32-bit access.
>
> For RAZ/WI, it's also seems to be the case but I'm not 100% sure. Anyway,
> emulating 32-bit access for them doesn't hurt. Note that we would need
> some extra care when they will be implemented (for instance GICR_PROPBASER).
>
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> ---
>     This is technically fixing boot of FreeBSD ARM64 guest with GICv3.
>
>     AFAICT, Linux is not using 32-bit access in the GICv3 code expect
>     for the ITS (which we don't support yet).
>
>     So this patch is a good candidate for Xen 4.6, maybe only via
>     backporting (i.e Xen 4.6.1) given that none of our supports guests OS
>     needs them right now.
> ---
>  xen/arch/arm/vgic-v3.c | 23 ++++++++++++++++-------
>  1 file changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
> index 7ef7b16..0ef5d42 100644
> --- a/xen/arch/arm/vgic-v3.c
> +++ b/xen/arch/arm/vgic-v3.c
> @@ -103,6 +103,15 @@ static struct vcpu *vgic_v3_get_target_vcpu(struct vcpu 
> *v, unsigned int irq)
>      return v_target;
>  }
>
> +static inline bool vgic_reg64_check_access(struct hsr_dabt dabt)
> +{
> +    /*
> +     * 64 bits registers can be accessible using 32-bit and 64-bit unless
> +     * stated otherwise (See 8.1.3 ARM IHI 0069A).
> +     */
> +    return ( dabt.size == DABT_DOUBLE_WORD || dabt.size == DABT_WORD );
> +}
> +

   This function is required for virtual ITS driver. Better to move to vgic.h

>  static int __vgic_v3_rdistr_rd_mmio_read(struct vcpu *v, mmio_info_t *info,
>                                           uint32_t gicr_reg)
>  {
> @@ -123,7 +132,7 @@ static int __vgic_v3_rdistr_rd_mmio_read(struct vcpu *v, 
> mmio_info_t *info,
>      {
>          uint64_t typer, aff;
>
> -        if ( dabt.size != DABT_DOUBLE_WORD ) goto bad_width;
> +        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 |
> @@ -209,7 +218,7 @@ bad_width:
>      return 0;
>
>  read_as_zero_64:
> -    if ( dabt.size != DABT_DOUBLE_WORD ) goto bad_width;
> +    if ( !vgic_reg64_check_access(dabt) ) goto bad_width;
>      *r = 0;
>      return 1;
>
> @@ -286,7 +295,7 @@ bad_width:
>      return 0;
>
>  write_ignore_64:
> -    if ( dabt.size != DABT_DOUBLE_WORD ) goto bad_width;
> +    if ( vgic_reg64_check_access(dabt) ) goto bad_width;
>      return 1;
>
>  write_ignore_32:
> @@ -774,7 +783,7 @@ static int vgic_v3_distr_mmio_read(struct vcpu *v, 
> mmio_info_t *info)
>      {
>          uint64_t irouter;
>
> -        if ( dabt.size != DABT_DOUBLE_WORD ) goto bad_width;
> +        if ( !vgic_reg64_check_access(dabt) ) goto bad_width;
>          rank = vgic_rank_offset(v, 64, gicd_reg - GICD_IROUTER,
>                                  DABT_DOUBLE_WORD);
>          if ( rank == NULL ) goto read_as_zero;
> @@ -850,7 +859,7 @@ bad_width:
>      return 0;
>
>  read_as_zero_64:
> -    if ( dabt.size != DABT_DOUBLE_WORD ) goto bad_width;
> +    if ( vgic_reg64_check_access(dabt) ) goto bad_width;
>      *r = 0;
>      return 1;
>
> @@ -935,7 +944,7 @@ static int vgic_v3_distr_mmio_write(struct vcpu *v, 
> mmio_info_t *info)
>          /* SGI/PPI is RES0 */
>          goto write_ignore_64;
>      case GICD_IROUTER32 ... GICD_IROUTERN:
> -        if ( dabt.size != DABT_DOUBLE_WORD ) goto bad_width;
> +        if ( !vgic_reg64_check_access(dabt) ) goto bad_width;
>          rank = vgic_rank_offset(v, 64, gicd_reg - GICD_IROUTER,
>                                  DABT_DOUBLE_WORD);
>          if ( rank == NULL ) goto write_ignore;
> @@ -1016,7 +1025,7 @@ write_ignore_32:
>      return 1;
>
>  write_ignore_64:
> -    if ( dabt.size != DABT_DOUBLE_WORD ) goto bad_width;
> +    if ( vgic_reg64_check_access(dabt) ) goto bad_width;
>      return 1;
>
>  write_ignore:
> --
> 2.1.4
>

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