Re: [Xen-devel] [PATCH V6 04/10] xen/arm: Use cpumask_t type for vcpu_mask in vgic_to_sgi

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-06-01 at 20:56 +0800, Chen Baozi wrote:
> From: Chen Baozi <baozich@xxxxxxxxx>
> 
> Use cpumask_t instead of unsigned long which can only express 64 cpus at
> the most. Add the {gicv2|gicv3}_sgir_to_cpumask in corresponding vGICs
> to translate GICD_SGIR/ICC_SGI1R_EL1 to vcpu_mask for vgic_to_sgi.
> 
> Signed-off-by: Chen Baozi <baozich@xxxxxxxxx>
> ---
>  xen/arch/arm/vgic-v2.c            | 16 +++++++++++++---
>  xen/arch/arm/vgic-v3.c            | 18 ++++++++++++++----
>  xen/arch/arm/vgic.c               | 31 ++++++++++++++++++++-----------
>  xen/include/asm-arm/gic.h         |  1 +
>  xen/include/asm-arm/gic_v3_defs.h |  2 ++
>  xen/include/asm-arm/vgic.h        |  2 +-
>  6 files changed, 51 insertions(+), 19 deletions(-)
> 
> diff --git a/xen/arch/arm/vgic-v2.c b/xen/arch/arm/vgic-v2.c
> index 3be1a51..17a3c9f 100644
> --- a/xen/arch/arm/vgic-v2.c
> +++ b/xen/arch/arm/vgic-v2.c
> @@ -33,6 +33,15 @@
>  #include <asm/gic.h>
>  #include <asm/vgic.h>
>  
> +static inline void gicv2_sgir_to_cpumask(cpumask_t *cpumask,
> +                                         const register_t sgir)
> +{
> +    unsigned long target_list;
> +
> +    target_list = ((sgir & GICD_SGI_TARGET_MASK) >> GICD_SGI_TARGET_SHIFT);
> +    bitmap_copy(cpumask_bits(cpumask), &target_list, GICD_SGI_TARGET_BITS);
> +}
> +
>  static int vgic_v2_distr_mmio_read(struct vcpu *v, mmio_info_t *info)
>  {
>      struct hsr_dabt dabt = info->dabt;
> @@ -201,16 +210,17 @@ static int vgic_v2_to_sgi(struct vcpu *v, register_t 
> sgir)
>      int virq;
>      int irqmode;
>      enum gic_sgi_mode sgi_mode;
> -    unsigned long vcpu_mask = 0;
> +    cpumask_t vcpu_mask;

How big is NR_CPUS (and hence this variable) going to be at the end of
this series? I can't seem to find the patch which bumps it, so I suppose
it remains 128?

Perhaps we want to bite the bullet now and change the vgic_to_sgi to
take an affinity path thing (aff3.aff2.aff1) + target list, instead of a
cpumask? That makes sense given the 16 CPU per AFF0 limitation, since
there is only a limited set of cpumask patterns which can be specified,
so we don't need the fully arbitrary bitmap.

> +    cpumask_clear(&vcpu_mask);
>      irqmode = (sgir & GICD_SGI_TARGET_LIST_MASK) >> 
> GICD_SGI_TARGET_LIST_SHIFT;
>      virq = (sgir & GICD_SGI_INTID_MASK);
> -    vcpu_mask = (sgir & GICD_SGI_TARGET_MASK) >> GICD_SGI_TARGET_SHIFT;
>  
>      /* Map GIC sgi value to enum value */
>      switch ( irqmode )
>      {
>      case GICD_SGI_TARGET_LIST_VAL:
> +        gicv2_sgir_to_cpumask(&vcpu_mask, sgir);
>          sgi_mode = SGI_TARGET_LIST;
>          break;
>      case GICD_SGI_TARGET_OTHERS_VAL:
> @@ -226,7 +236,7 @@ static int vgic_v2_to_sgi(struct vcpu *v, register_t sgir)
>          return 0;
>      }
>  
> -    return vgic_to_sgi(v, sgir, sgi_mode, virq, vcpu_mask);
> +    return vgic_to_sgi(v, sgir, sgi_mode, virq, &vcpu_mask);
>  }
>  
>  static int vgic_v2_distr_mmio_write(struct vcpu *v, mmio_info_t *info)
> diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
> index ef9a71a..2bf5294 100644
> --- a/xen/arch/arm/vgic-v3.c
> +++ b/xen/arch/arm/vgic-v3.c
> @@ -972,22 +972,32 @@ write_ignore:
>      return 1;
>  }
>  
> +static inline void gicv3_sgir_to_cpumask(cpumask_t *cpumask,
> +                                         const register_t sgir)
> +{
> +    unsigned long target_list;
> +
> +    target_list = sgir & ICH_SGI_TARGETLIST_MASK;
> +    bitmap_copy(cpumask_bits(cpumask), &target_list, ICH_SGI_TARGET_BITS);

Do you not need to left shift the target_list bits into the cpumask
based on AFF1+?

Otherwise aren't you delivering an SGI targeted at, say, 0.0.1.0xab to
0.0.0.0xab?

> +}
> +
>  static int vgic_v3_to_sgi(struct vcpu *v, register_t sgir)
>  {
>      int virq;
>      int irqmode;
>      enum gic_sgi_mode sgi_mode;
> -    unsigned long vcpu_mask = 0;
> +    cpumask_t vcpu_mask;
>  
> +    cpumask_clear(&vcpu_mask);
>      irqmode = (sgir >> ICH_SGI_IRQMODE_SHIFT) & ICH_SGI_IRQMODE_MASK;
>      virq = (sgir >> ICH_SGI_IRQ_SHIFT ) & ICH_SGI_IRQ_MASK;
> -    /* SGI's are injected at Rdist level 0. ignoring affinity 1, 2, 3 */
> -    vcpu_mask = sgir & ICH_SGI_TARGETLIST_MASK;
>  
>      /* Map GIC sgi value to enum value */
>      switch ( irqmode )
>      {
>      case ICH_SGI_TARGET_LIST:
> +        /* SGI's are injected at Rdist level 0. ignoring affinity 1, 2, 3 */
> +        gicv3_sgir_to_cpumask(&vcpu_mask, sgir);
>          sgi_mode = SGI_TARGET_LIST;
>          break;
>      case ICH_SGI_TARGET_OTHERS:
> @@ -998,7 +1008,7 @@ static int vgic_v3_to_sgi(struct vcpu *v, register_t 
> sgir)
>          return 0;
>      }
>  
> -    return vgic_to_sgi(v, sgir, sgi_mode, virq, vcpu_mask);
> +    return vgic_to_sgi(v, sgir, sgi_mode, virq, &vcpu_mask);
>  }
>  
>  static int vgic_v3_emulate_sysreg(struct cpu_user_regs *regs, union hsr hsr)
> diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
> index 7b387b7..1bd86f8 100644
> --- a/xen/arch/arm/vgic.c
> +++ b/xen/arch/arm/vgic.c
> @@ -318,15 +318,20 @@ void vgic_enable_irqs(struct vcpu *v, uint32_t r, int n)
>      }
>  }
>  
> -/* TODO: unsigned long is used to fit vcpu_mask.*/
>  int vgic_to_sgi(struct vcpu *v, register_t sgir, enum gic_sgi_mode irqmode, 
> int virq,
> -                unsigned long vcpu_mask)
> +                cpumask_t *vcpu_mask)
>  {
>      struct domain *d = v->domain;
>      int vcpuid;
>      int i;
>  
> -    ASSERT(d->max_vcpus < 8*sizeof(vcpu_mask));
> +    /*
> +     * cpumask_t is based on NR_CPUS and there is no relation between
> +     * NR_CPUS and MAX_VIRT_CPUS. Furthermore, NR_CPUS can be configured
> +     * at build time by the user. So we add a BUILD_BUG_ON here in order
> +     * to avoid insecure hypervisor.

Insecure?

> +     */
> +    BUILD_BUG_ON(sizeof(cpumask_t)*8 < MAX_VIRT_CPUS);

Is this the same as (NR_CPUS < MAX_VIRT_CPUS)?

Ian


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