Re: [Xen-devel] [PATCH v2 05/19] xen/arm: Avoid setting/clearing HCR_RW at every context switch

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 30 Mar 2017, Wei Chen wrote:
> The HCR_EL2 flags for 64-bit and 32-bit domains are different. But
> when we initialized the HCR_EL2 for vcpu0 of Dom0 and all vcpus of
> DomU in vcpu_initialise, we didn't know the domain's address size
> information. We had to use compatible flags to initialize HCR_EL2,
> and set HCR_RW for 64-bit domain or clear HCR_RW for 32-bit domain
> at every context switch.
> 
> But, after we added the HCR_EL2 to vcpu's context, this behaviour
> seems a little fussy. We can update the HCR_RW bit in vcpu's context
> as soon as we get the domain's address size to avoid setting/clearing
> HCR_RW at every context switch.
> 
> Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

> ---
>  xen/arch/arm/arm64/domctl.c  | 6 ++++++
>  xen/arch/arm/domain.c        | 5 +++++
>  xen/arch/arm/domain_build.c  | 7 +++++++
>  xen/arch/arm/p2m.c           | 5 -----
>  xen/include/asm-arm/domain.h | 1 +
>  5 files changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/arm/arm64/domctl.c b/xen/arch/arm/arm64/domctl.c
> index 44e1e7b..ab8781f 100644
> --- a/xen/arch/arm/arm64/domctl.c
> +++ b/xen/arch/arm/arm64/domctl.c
> @@ -14,6 +14,8 @@
>  
>  static long switch_mode(struct domain *d, enum domain_type type)
>  {
> +    struct vcpu *v;
> +
>      if ( d == NULL )
>          return -EINVAL;
>      if ( d->tot_pages != 0 )
> @@ -23,6 +25,10 @@ static long switch_mode(struct domain *d, enum domain_type 
> type)
>  
>      d->arch.type = type;
>  
> +    if ( is_64bit_domain(d) )
> +        for_each_vcpu(d, v)
> +            vcpu_switch_to_aarch64_mode(v);
> +
>      return 0;
>  }
>  
> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> index c69e204..18b34e7 100644
> --- a/xen/arch/arm/domain.c
> +++ b/xen/arch/arm/domain.c
> @@ -553,6 +553,11 @@ void vcpu_destroy(struct vcpu *v)
>      free_xenheap_pages(v->arch.stack, STACK_ORDER);
>  }
>  
> +void vcpu_switch_to_aarch64_mode(struct vcpu *v)
> +{
> +    v->arch.hcr_el2 |= HCR_RW;
> +}
> +
>  int arch_domain_create(struct domain *d, unsigned int domcr_flags,
>                         struct xen_arch_domainconfig *config)
>  {
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 8af223e..14475a5 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -2148,6 +2148,10 @@ int construct_dom0(struct domain *d)
>          return -EINVAL;
>      }
>      d->arch.type = kinfo.type;
> +
> +    if ( is_64bit_domain(d) )
> +        vcpu_switch_to_aarch64_mode(v);
> +
>  #endif
>  
>      allocate_memory(d, &kinfo);
> @@ -2247,6 +2251,9 @@ int construct_dom0(struct domain *d)
>              printk("Failed to allocate dom0 vcpu %d on pcpu %d\n", i, cpu);
>              break;
>          }
> +
> +        if ( is_64bit_domain(d) )
> +            vcpu_switch_to_aarch64_mode(d->vcpu[i]);
>      }
>  
>      return 0;
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index 83c4b7d..34d5776 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -137,11 +137,6 @@ void p2m_restore_state(struct vcpu *n)
>      WRITE_SYSREG64(p2m->vttbr, VTTBR_EL2);
>      isb();
>  
> -    if ( is_32bit_domain(n->domain) )
> -        n->arch.hcr_el2 &= ~HCR_RW;
> -    else
> -        n->arch.hcr_el2 |= HCR_RW;
> -
>      WRITE_SYSREG(n->arch.sctlr, SCTLR_EL1);
>      isb();
>  
> diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> index 7b1dacc..68185e2 100644
> --- a/xen/include/asm-arm/domain.h
> +++ b/xen/include/asm-arm/domain.h
> @@ -268,6 +268,7 @@ struct arch_vcpu
>  
>  void vcpu_show_execution_state(struct vcpu *);
>  void vcpu_show_registers(const struct vcpu *);
> +void vcpu_switch_to_aarch64_mode(struct vcpu *);
>  
>  unsigned int domain_max_vcpus(const struct domain *);
>  
> -- 
> 2.7.4
> 
> 
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> https://lists.xen.org/xen-devel
> 

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