Re: [PATCH 5/7] target/ppc: Rework ppc_radix64_walk_tree() for partition-scoped translation

[Greg Kurz]

On Mon, 30 Mar 2020 11:49:44 +0200
Cédric Le Goater <address@hidden> wrote:

> The ppc_radix64_walk_tree() routine walks through the nested radix
> tables to look for a PTE.
> 
> Split it two and introduce a new routine ppc_radix64_next_level()

Split it in two...

> which we will use for partition-scoped Radix translation when
> translating the process tree addresses.
> 
> Signed-off-by: Suraj Jitindar Singh <address@hidden>
> Signed-off-by: Cédric Le Goater <address@hidden>
> ---
>  target/ppc/mmu-radix64.c | 50 ++++++++++++++++++++++++++--------------
>  1 file changed, 33 insertions(+), 17 deletions(-)
> 
> diff --git a/target/ppc/mmu-radix64.c b/target/ppc/mmu-radix64.c
> index b4e6abcd2d35..136498111f60 100644
> --- a/target/ppc/mmu-radix64.c
> +++ b/target/ppc/mmu-radix64.c
> @@ -162,44 +162,60 @@ static void ppc_radix64_set_rc(PowerPCCPU *cpu, int 
> rwx, uint64_t pte,
>      }
>  }
>  
> -static uint64_t ppc_radix64_walk_tree(PowerPCCPU *cpu, vaddr eaddr,
> -                                      uint64_t base_addr, uint64_t nls,
> -                                      hwaddr *raddr, int *psize,
> -                                      int *fault_cause, hwaddr *pte_addr)
> +static uint64_t ppc_radix64_next_level(PowerPCCPU *cpu, vaddr eaddr,
> +                                       uint64_t *pte_addr, uint64_t *nls,
> +                                       int *psize, int *fault_cause)
>  {
>      CPUState *cs = CPU(cpu);
>      uint64_t index, pde;
>  
> -    if (nls < 5) { /* Directory maps less than 2**5 entries */
> +    if (*nls < 5) { /* Directory maps less than 2**5 entries */
>          *fault_cause |= DSISR_R_BADCONFIG;
>          return 0;
>      }
>  

I think this should stay in the caller...

>      /* Read page <directory/table> entry from guest address space */
> -    index = eaddr >> (*psize - nls); /* Shift */
> -    index &= ((1UL << nls) - 1); /* Mask */
> -    pde = ldq_phys(cs->as, base_addr + (index * sizeof(pde)));
> -    if (!(pde & R_PTE_VALID)) { /* Invalid Entry */
> +    pde = ldq_phys(cs->as, *pte_addr);
> +    if (!(pde & R_PTE_VALID)) {         /* Invalid Entry */
>          *fault_cause |= DSISR_NOPTE;
>          return 0;
>      }
>  
> -    *psize -= nls;
> +    *psize -= *nls;
> +    if (!(pde & R_PTE_LEAF)) { /* Prepare for next iteration */
> +        *nls = pde & R_PDE_NLS;
> +        index = eaddr >> (*psize - *nls);       /* Shift */
> +        index &= ((1UL << *nls) - 1);           /* Mask */
> +        *pte_addr = (pde & R_PDE_NLB) + (index * sizeof(pde));
> +    }
> +    return pde;
> +}
> +
> +static uint64_t ppc_radix64_walk_tree(PowerPCCPU *cpu, vaddr eaddr,
> +                                      uint64_t base_addr, uint64_t nls,
> +                                      hwaddr *raddr, int *psize,
> +                                      int *fault_cause, hwaddr *pte_addr)
> +{
> +    uint64_t index, pde;
> +
> +    index = eaddr >> (*psize - nls);    /* Shift */
> +    index &= ((1UL << nls) - 1);       /* Mask */
> +    *pte_addr = base_addr + (index * sizeof(pde));
> +    do {

... here. So that we have a well established "bad config" path at
the root level, just like the current code has.

Since the ppc_radix64_walk_tree() now calls ppc_radix64_next_level()
in a loop instead of recursing, and since ppc_radix64_next_level()
returns the nls value for the next level, it really makes sense to
have this check in ppc_radix64_walk_tree() and maybe put an assert
in ppc_radix64_next_level().

> +        pde = ppc_radix64_next_level(cpu, eaddr, pte_addr, &nls, psize,
> +                                     fault_cause);
> +    } while ((pde & R_PTE_VALID) && !(pde & R_PTE_LEAF));
>  
> -    /* Check if Leaf Entry -> Page Table Entry -> Stop the Search */
> -    if (pde & R_PTE_LEAF) {
> +    /* Did we find a valid leaf? */
> +    if ((pde & R_PTE_VALID) && (pde & R_PTE_LEAF)) {
>          uint64_t rpn = pde & R_PTE_RPN;
>          uint64_t mask = (1UL << *psize) - 1;
>  
>          /* Or high bits of rpn and low bits to ea to form whole real addr */
>          *raddr = (rpn & ~mask) | (eaddr & mask);
> -        *pte_addr = base_addr + (index * sizeof(pde));
> -        return pde;
>      }
>  
> -    /* Next Level of Radix Tree */
> -    return ppc_radix64_walk_tree(cpu, eaddr, pde & R_PDE_NLB, pde & 
> R_PDE_NLS,
> -                                 raddr, psize, fault_cause, pte_addr);
> +    return pde;
>  }
>  
>  static bool validate_pate(PowerPCCPU *cpu, uint64_t lpid, ppc_v3_pate_t 
> *pate)