Re: [Xen-devel] [PATCH v3 03/19] xen/arm: Set and restore HCR_EL2 register for each vCPU separately

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 31 Mar 2017, Wei Chen wrote:
> Different domains may have different HCR_EL2 flags. For example, the
> 64-bit domain needs HCR_RW flag but the 32-bit does not need it. So
> we give each domain a default HCR_EL2 value and save it in the vCPU's
> context.
> 
> HCR_EL2 register has only one bit can be updated automatically without
> explicit write (HCR_VSE). But we haven't used this bit currently, so
> we can consider that the HCR_EL2 register will not be modified while
> the guest is running. So save the HCR_EL2 while guest exiting to
> hypervisor is not neccessary. We just have to restore this register for
> each vCPU while context switching.
> 
> The p2m_restore_state which will be invoked in context switch progress
> has included the writing of HCR_EL2 already. It updates the HCR_EL2.RW
> bit to tell the hardware how to interpret the stage-1 page table as the
> encodings are different between AArch64 and AArch32. We can reuse this
> write to restore the HCR_EL2 for each vCPU. Of course, the value of each
> vCPU's HCR_EL2 should be adjusted to have proper HCR_EL2.RW bit in this
> function. In the later patch of this series, we will set the HCR_EL2.RW
> for each vCPU while the domain is creating.
> 
> Signed-off-by: wei chen <Wei.Chen@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

> ---
> v2->v3:
> 1. Squash #2 #3 patchs of v2 into this patch.
> 2. Remove HCR_EL2 initialization of idle vCPU, it would be used.
> 3. Revert the change of vwfi.
> 4. Use the helper that introduced in previous patch to initialize
>    HCR_EL2 for each vCPU.
> 5. Restore the initialization of HCR_EL2 in init_traps.
> ---
>  xen/arch/arm/domain.c        | 2 ++
>  xen/arch/arm/p2m.c           | 9 +++------
>  xen/include/asm-arm/domain.h | 3 +++
>  3 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> index bb327da..5d18bb0 100644
> --- a/xen/arch/arm/domain.c
> +++ b/xen/arch/arm/domain.c
> @@ -513,6 +513,8 @@ int vcpu_initialise(struct vcpu *v)
>  
>      v->arch.actlr = READ_SYSREG32(ACTLR_EL1);
>  
> +    v->arch.hcr_el2 = get_default_hcr_flags();
> +
>      processor_vcpu_initialise(v);
>  
>      if ( (rc = vcpu_vgic_init(v)) != 0 )
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index 6263760..83c4b7d 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -128,27 +128,24 @@ void p2m_save_state(struct vcpu *p)
>  
>  void p2m_restore_state(struct vcpu *n)
>  {
> -    register_t hcr;
>      struct p2m_domain *p2m = &n->domain->arch.p2m;
>      uint8_t *last_vcpu_ran;
>  
>      if ( is_idle_vcpu(n) )
>          return;
>  
> -    hcr = READ_SYSREG(HCR_EL2);
> -
>      WRITE_SYSREG64(p2m->vttbr, VTTBR_EL2);
>      isb();
>  
>      if ( is_32bit_domain(n->domain) )
> -        hcr &= ~HCR_RW;
> +        n->arch.hcr_el2 &= ~HCR_RW;
>      else
> -        hcr |= HCR_RW;
> +        n->arch.hcr_el2 |= HCR_RW;
>  
>      WRITE_SYSREG(n->arch.sctlr, SCTLR_EL1);
>      isb();
>  
> -    WRITE_SYSREG(hcr, HCR_EL2);
> +    WRITE_SYSREG(n->arch.hcr_el2, HCR_EL2);
>      isb();
>  
>      last_vcpu_ran = &p2m->last_vcpu_ran[smp_processor_id()];
> diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> index 09fe502..7b1dacc 100644
> --- a/xen/include/asm-arm/domain.h
> +++ b/xen/include/asm-arm/domain.h
> @@ -204,6 +204,9 @@ struct arch_vcpu
>      register_t tpidr_el1;
>      register_t tpidrro_el0;
>  
> +    /* HYP configuration */
> +    register_t hcr_el2;
> +
>      uint32_t teecr, teehbr; /* ThumbEE, 32-bit guests only */
>  #ifdef CONFIG_ARM_32
>      /*
> -- 
> 2.7.4
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> https://lists.xen.org/xen-devel
> 

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel