Re: [Xen-devel] [PATCH 16/22] xen/arm: p2m: Move the vttbr field from arch_domain to p2m_domain

[Sergej Proskurin <proskurin@xxxxxxxxxxxxx>]

Hi Julien,

On 07/20/2016 06:10 PM, Julien Grall wrote:
> The field vttbr holds the base address of the translation table for
> guest. Its value will depends on how the p2m has been initialized and
> will only be used by the code code.
> 
> So move the field from arch_domain to p2m_domain. This will also ease
> the implementation of altp2m.
> ---
>  xen/arch/arm/p2m.c           | 11 +++++++----
>  xen/arch/arm/traps.c         |  2 +-
>  xen/include/asm-arm/domain.h |  1 -
>  xen/include/asm-arm/p2m.h    |  3 +++
>  4 files changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index c407e6a..c52081a 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -107,10 +107,14 @@ void dump_p2m_lookup(struct domain *d, paddr_t addr)
>  
>  static void p2m_load_VTTBR(struct domain *d)
>  {
> +    struct p2m_domain *p2m = &d->arch.p2m;
> +

This is ok to me. Further altp2m implementation can easily extend this
code base.

Also, as your patch (patch #17) as well eliminates the possibility that
the idle domain reaches this function the following check could be
potentially removed (as far as I know, p2m_load_VTTBR is reached only
through p2m_restore_state).

>      if ( is_idle_domain(d) )
>          return;
> -    BUG_ON(!d->arch.vttbr);
> -    WRITE_SYSREG64(d->arch.vttbr, VTTBR_EL2);
> +
> +    ASSERT(p2m->vttbr);
> +
> +    WRITE_SYSREG64(p2m->vttbr, VTTBR_EL2);
>      isb(); /* Ensure update is visible */
>  }
>  
> @@ -1298,8 +1302,7 @@ static int p2m_alloc_table(struct domain *d)
>  
>      p2m->root = page;
>  
> -    d->arch.vttbr = page_to_maddr(p2m->root)
> -        | ((uint64_t)p2m->vmid&0xff)<<48;
> +    p2m->vttbr = page_to_maddr(p2m->root) | ((uint64_t)p2m->vmid & 0xff) << 
> 48;
>  
>      /*
>       * Make sure that all TLBs corresponding to the new VMID are flushed
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 06a8ee5..65c6fb4 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -880,7 +880,7 @@ void vcpu_show_registers(const struct vcpu *v)
>      ctxt.ifsr32_el2 = v->arch.ifsr;
>  #endif
>  
> -    ctxt.vttbr_el2 = v->domain->arch.vttbr;
> +    ctxt.vttbr_el2 = v->domain->arch.p2m.vttbr;
>  
>      _show_registers(&v->arch.cpu_info->guest_cpu_user_regs, &ctxt, 1, v);
>  }
> diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> index 4e9d8bf..9452fcd 100644
> --- a/xen/include/asm-arm/domain.h
> +++ b/xen/include/asm-arm/domain.h
> @@ -48,7 +48,6 @@ struct arch_domain
>  
>      /* Virtual MMU */
>      struct p2m_domain p2m;
> -    uint64_t vttbr;
>  
>      struct hvm_domain hvm_domain;
>      gfn_t *grant_table_gfn;
> diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
> index ce28e8a..53c4d78 100644
> --- a/xen/include/asm-arm/p2m.h
> +++ b/xen/include/asm-arm/p2m.h
> @@ -32,6 +32,9 @@ struct p2m_domain {
>      /* Current VMID in use */
>      uint8_t vmid;
>  
> +    /* Current Translation Table Base Register for the p2m */
> +    uint64_t vttbr;
> +
>      /*
>       * Highest guest frame that's ever been mapped in the p2m
>       * Only takes into account ram and foreign mapping
> 

Cheers,
~Sergej

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