Re: [PATCH for-4.19? v5 07/10] xen: Make the maximum number of altp2m views configurable for x86

[Jan Beulich <jbeulich@xxxxxxxx>]

On 02.06.2024 22:04, Petr Beneš wrote:
> @@ -5245,7 +5251,7 @@ void hvm_fast_singlestep(struct vcpu *v, uint16_t 
> p2midx)
>      if ( !hvm_is_singlestep_supported() )
>          return;
> 
> -    if ( p2midx >= MAX_ALTP2M )
> +    if ( p2midx >= v->domain->nr_altp2m )
>          return;

As (iirc) indicated before, just like you don't add a d local variable
here or ...

> --- a/xen/arch/x86/include/asm/p2m.h
> +++ b/xen/arch/x86/include/asm/p2m.h
> @@ -887,7 +887,7 @@ static inline struct p2m_domain *p2m_get_altp2m(struct 
> vcpu *v)
>      if ( index == INVALID_ALTP2M )
>          return NULL;
> 
> -    BUG_ON(index >= MAX_ALTP2M);
> +    BUG_ON(index >= v->domain->nr_altp2m);
> 
>      return altp2m_get_p2m(v->domain, index);
>  }
> @@ -898,7 +898,7 @@ static inline bool p2m_set_altp2m(struct vcpu *v, 
> unsigned int idx)
>      struct p2m_domain *orig;
>      struct p2m_domain *ap2m;
> 
> -    BUG_ON(idx >= MAX_ALTP2M);
> +    BUG_ON(idx >= v->domain->nr_altp2m);
> 
>      if ( idx == vcpu_altp2m(v).p2midx )
>          return false;

... in either of these, I see little reason to have such ...

> --- a/xen/arch/x86/mm/altp2m.c
> +++ b/xen/arch/x86/mm/altp2m.c
> @@ -15,6 +15,11 @@
>  void
>  altp2m_vcpu_initialise(struct vcpu *v)
>  {
> +    struct domain *d = v->domain;
> +
> +    if ( d->nr_altp2m == 0 )
> +        return;
> +
>      if ( v != current )
>          vcpu_pause(v);
> 
> @@ -30,8 +35,12 @@ altp2m_vcpu_initialise(struct vcpu *v)
>  void
>  altp2m_vcpu_destroy(struct vcpu *v)
>  {
> +    struct domain *d = v->domain;
>      struct p2m_domain *p2m;
> 
> +    if ( d->nr_altp2m == 0 )
> +        return;
> +
>      if ( v != current )
>          vcpu_pause(v);

... in both of these.

> @@ -122,7 +131,12 @@ int p2m_init_altp2m(struct domain *d)
>      struct p2m_domain *hostp2m = p2m_get_hostp2m(d);
> 
>      mm_lock_init(&d->arch.altp2m_list_lock);
> -    for ( i = 0; i < MAX_ALTP2M; i++ )
> +    d->arch.altp2m_p2m = xzalloc_array(struct p2m_domain *, d->nr_altp2m);
> +
> +    if ( !d->arch.altp2m_p2m )
> +        return -ENOMEM;

This isn't really needed, is it? Both ...

> +    for ( i = 0; i < d->nr_altp2m; i++ )

... this and ...

>      {
>          d->arch.altp2m_p2m[i] = p2m = p2m_init_one(d);
>          if ( p2m == NULL )
> @@ -143,7 +157,10 @@ void p2m_teardown_altp2m(struct domain *d)
>      unsigned int i;
>      struct p2m_domain *p2m;
> 
> -    for ( i = 0; i < MAX_ALTP2M; i++ )
> +    if ( !d->arch.altp2m_p2m )
> +        return;
> +
> +    for ( i = 0; i < d->nr_altp2m; i++ )
>      {
>          if ( !d->arch.altp2m_p2m[i] )
>              continue;
> @@ -151,6 +168,8 @@ void p2m_teardown_altp2m(struct domain *d)
>          d->arch.altp2m_p2m[i] = NULL;
>          p2m_free_one(p2m);
>      }
> +
> +    XFREE(d->arch.altp2m_p2m);
>  }

... this ought to be fine without?

> @@ -538,8 +538,8 @@ void hap_final_teardown(struct domain *d)
>      unsigned int i;
> 
>      if ( hvm_altp2m_supported() )
> -        for ( i = 0; i < MAX_ALTP2M; i++ )
> -            p2m_teardown(d->arch.altp2m_p2m[i], true, NULL);
> +        for ( i = 0; i < d->nr_altp2m; i++ )
> +            p2m_teardown(altp2m_get_p2m(d, i), true, NULL);

Shouldn't the switch to altp2m_get_p2m() be part of the respective
earlier patch?

Jan