Re: [Xen-devel] [PATCH 2/9] xen/arm: traps: Second attempt to correctly use the content of HPFAR_EL2

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 22 Jun 2016, Julien Grall wrote:
> Commit c051618 "xen/arm: traps: Correctly interpret the content of the
> register HPFAR_EL2" attempted to fix the interpretation of HPFAR_EL2.
> 
> However, the register contains a 4KB-aligned address. This means that
> the reported address is not directly usable to know the faulting IPA.
> The offset in the 4KB page can be found by looking at the associated virtual
> address (FAR_EL2/HDFAR).
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
> 
> Cc: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
> 
> I overlooked the usage of HPFAR_EL2. This is currently only affecting
> memaccess. Rather that return that exact address, the address will
> always be the base addres of the 4KB page.
> 
> This would need to be backported up to Xen 4.6.
> ---
>  xen/arch/arm/traps.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 0709deb..742f7d3 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -2371,11 +2371,15 @@ done:
>      if (first) unmap_domain_page(first);
>  }
>  
> -static inline paddr_t get_faulting_ipa(void)
> +static inline paddr_t get_faulting_ipa(vaddr_t gva)
>  {
>      register_t hpfar = READ_SYSREG(HPFAR_EL2);
> +    paddr_t ipa;
>  
> -    return ((paddr_t)(hpfar & HPFAR_MASK) << (12 - 4));
> +    ipa = (paddr_t)(hpfar & HPFAR_MASK) << (12 - 4);
> +    ipa |= gva & ~PAGE_MASK;
> +
> +    return ipa;
>  }
>  
>  static void do_trap_instr_abort_guest(struct cpu_user_regs *regs,
> @@ -2396,7 +2400,7 @@ static void do_trap_instr_abort_guest(struct 
> cpu_user_regs *regs,
>          };
>  
>          if ( hsr.iabt.s1ptw )
> -            gpa = get_faulting_ipa();
> +            gpa = get_faulting_ipa(gva);
>          else
>          {
>              /*
> @@ -2445,7 +2449,7 @@ static void do_trap_data_abort_guest(struct 
> cpu_user_regs *regs,
>  #endif
>  
>      if ( dabt.s1ptw )
> -        info.gpa = get_faulting_ipa();
> +        info.gpa = get_faulting_ipa(info.gva);
>      else
>      {
>          rc = gva_to_ipa(info.gva, &info.gpa, GV2M_READ);
> -- 
> 1.9.1
> 

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