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

["Cédric Le Goater" <clg@kaod.org>]

On 3/30/20 7:00 PM, Greg Kurz wrote:
> On Mon, 30 Mar 2020 11:49:44 +0200
> Cédric Le Goater <clg@kaod.org> 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 <sjitindarsingh@gmail.com>
>> Signed-off-by: Cédric Le Goater <clg@kaod.org>
>> ---
>>  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().

ppc_radix64_next_level() also covers the needs of partition-scoped 
translation which translates each process table address. See PATCH 7.

I rather not duplicate more code and leave it as it is.
 
Thanks,

C.

> 
>> +        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)
>