Re: [PATCH for-8.1 2/3] target/arm: Fix S1_ptw_translate() debug path

[Jean-Philippe Brucker]

On Mon, Jul 10, 2023 at 04:21:29PM +0100, Peter Maydell wrote:
> In commit XXX we rearranged the logic in S1_ptw_translate() so that
> the debug-access "call get_phys_addr_*" codepath is used both when S1
> is doing ptw reads from stage 2 and when it is doing ptw reads from
> physical memory.  However, we didn't update the calculation of
> s2ptw->in_space and s2ptw->in_secure to account for the "ptw reads
> from physical memory" case.  This meant that debug accesses when in
> Secure state broke.
> 
> Create a new function S2_security_space() which returns the
> correct security space to use for the ptw load, and use it to
> determine the correct .in_secure and .in_space fields for the
> stage 2 lookup for the ptw load.
> 
> Reported-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Fixes: fe4a5472ccd6 ("target/arm: Use get_phys_addr_with_struct in 
> S1_ptw_translate")
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Thanks, this fixes tf-a boot with semihosting

Tested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>

> ---
>  target/arm/ptw.c | 37 ++++++++++++++++++++++++++++++++-----
>  1 file changed, 32 insertions(+), 5 deletions(-)
> 
> diff --git a/target/arm/ptw.c b/target/arm/ptw.c
> index 21749375f97..c0b9cee5843 100644
> --- a/target/arm/ptw.c
> +++ b/target/arm/ptw.c
> @@ -485,11 +485,39 @@ static bool S2_attrs_are_device(uint64_t hcr, uint8_t 
> attrs)
>      }
>  }
>  
> +static ARMSecuritySpace S2_security_space(ARMSecuritySpace s1_space,
> +                                          ARMMMUIdx s2_mmu_idx)
> +{
> +    /*
> +     * Return the security space to use for stage 2 when doing
> +     * the S1 page table descriptor load.
> +     */
> +    if (regime_is_stage2(s2_mmu_idx)) {
> +        /*
> +         * The security space for ptw reads is almost always the same
> +         * as that of the security space of the stage 1 translation.
> +         * The only exception is when stage 1 is Secure; in that case
> +         * the ptw read might be to the Secure or the NonSecure space
> +         * (but never Realm or Root), and the s2_mmu_idx tells us which.
> +         * Root translations are always single-stage.
> +         */
> +        if (s1_space == ARMSS_Secure) {
> +            return arm_secure_to_space(s2_mmu_idx == ARMMMUIdx_Stage2_S);
> +        } else {
> +            assert(s2_mmu_idx != ARMMMUIdx_Stage2_S);
> +            assert(s1_space != ARMSS_Root);
> +            return s1_space;
> +        }
> +    } else {
> +        /* ptw loads are from phys: the mmu idx itself says which space */
> +        return arm_phys_to_space(s2_mmu_idx);
> +    }
> +}
> +
>  /* Translate a S1 pagetable walk through S2 if needed.  */
>  static bool S1_ptw_translate(CPUARMState *env, S1Translate *ptw,
>                               hwaddr addr, ARMMMUFaultInfo *fi)
>  {
> -    ARMSecuritySpace space = ptw->in_space;
>      bool is_secure = ptw->in_secure;
>      ARMMMUIdx mmu_idx = ptw->in_mmu_idx;
>      ARMMMUIdx s2_mmu_idx = ptw->in_ptw_idx;
> @@ -502,13 +530,12 @@ static bool S1_ptw_translate(CPUARMState *env, 
> S1Translate *ptw,
>           * From gdbstub, do not use softmmu so that we don't modify the
>           * state of the cpu at all, including softmmu tlb contents.
>           */
> +        ARMSecuritySpace s2_space = S2_security_space(ptw->in_space, 
> s2_mmu_idx);
>          S1Translate s2ptw = {
>              .in_mmu_idx = s2_mmu_idx,
>              .in_ptw_idx = ptw_idx_for_stage_2(env, s2_mmu_idx),
> -            .in_secure = s2_mmu_idx == ARMMMUIdx_Stage2_S,
> -            .in_space = (s2_mmu_idx == ARMMMUIdx_Stage2_S ? ARMSS_Secure
> -                         : space == ARMSS_Realm ? ARMSS_Realm
> -                         : ARMSS_NonSecure),
> +            .in_secure = arm_space_is_secure(s2_space),
> +            .in_space = s2_space,
>              .in_debug = true,
>          };
>          GetPhysAddrResult s2 = { };
> -- 
> 2.34.1
>