Re: [Qemu-devel] [PATCH v2] target/s390x: Add support for the TEST BLOCK instruction

[Thomas Huth]

On 18.05.2017 15:20, Aurelien Jarno wrote:
> On 2017-05-18 13:39, Thomas Huth wrote:
>> TEST BLOCK was likely once used to execute basic memory
>> tests, but nowadays it's just a (slow) way to clear a page.
>>
>> Signed-off-by: Thomas Huth <address@hidden>
>> ---
>>  v2:
>>  - Use DEF_HELPER_FLAGS_2 instead for DEF_HELPER_2 for returning CC value
>>  - Convert real to absolute address
>>  - Added a check for valid RAM page
>>  - Added low-address protection check
>>
>>  target/s390x/cpu.h         |  1 +
>>  target/s390x/helper.h      |  1 +
>>  target/s390x/insn-data.def |  2 ++
>>  target/s390x/mem_helper.c  | 28 ++++++++++++++++++++++++++++
>>  target/s390x/mmu_helper.c  |  2 +-
>>  target/s390x/translate.c   | 10 ++++++++++
>>  6 files changed, 43 insertions(+), 1 deletion(-)
>>
>> diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
>> index 240b8a5..4f38ba0 100644
>> --- a/target/s390x/cpu.h
>> +++ b/target/s390x/cpu.h
>> @@ -1082,6 +1082,7 @@ struct sysib_322 {
>>  #define SIGP_ORDER_MASK 0x000000ff
>>  
>>  void load_psw(CPUS390XState *env, uint64_t mask, uint64_t addr);
>> +target_ulong mmu_real2abs(CPUS390XState *env, target_ulong raddr);
>>  int mmu_translate(CPUS390XState *env, target_ulong vaddr, int rw, uint64_t 
>> asc,
>>                    target_ulong *raddr, int *flags, bool exc);
>>  int sclp_service_call(CPUS390XState *env, uint64_t sccb, uint32_t code);
>> diff --git a/target/s390x/helper.h b/target/s390x/helper.h
>> index 0b70770..1fae191 100644
>> --- a/target/s390x/helper.h
>> +++ b/target/s390x/helper.h
>> @@ -102,6 +102,7 @@ DEF_HELPER_FLAGS_4(lctl, TCG_CALL_NO_WG, void, env, i32, 
>> i64, i32)
>>  DEF_HELPER_FLAGS_4(lctlg, TCG_CALL_NO_WG, void, env, i32, i64, i32)
>>  DEF_HELPER_FLAGS_4(stctl, TCG_CALL_NO_WG, void, env, i32, i64, i32)
>>  DEF_HELPER_FLAGS_4(stctg, TCG_CALL_NO_WG, void, env, i32, i64, i32)
>> +DEF_HELPER_FLAGS_2(testblock, TCG_CALL_NO_WG, i32, env, i64)
> 
> As the helper does not read any values from the global, you can even use
> TCG_CALL_NO_RWG.

Ok.

>>  DEF_HELPER_FLAGS_2(tprot, TCG_CALL_NO_RWG, i32, i64, i64)
>>  DEF_HELPER_FLAGS_2(iske, TCG_CALL_NO_RWG_SE, i64, env, i64)
>>  DEF_HELPER_FLAGS_3(sske, TCG_CALL_NO_RWG, void, env, i64, i64)
>> diff --git a/target/s390x/insn-data.def b/target/s390x/insn-data.def
>> index 55a7c52..cac0f51 100644
>> --- a/target/s390x/insn-data.def
>> +++ b/target/s390x/insn-data.def
>> @@ -918,6 +918,8 @@
>>  /* STORE USING REAL ADDRESS */
>>      C(0xb246, STURA,   RRE,   Z,   r1_o, r2_o, 0, 0, stura, 0)
>>      C(0xb925, STURG,   RRE,   Z,   r1_o, r2_o, 0, 0, sturg, 0)
>> +/* TEST BLOCK */
>> +    C(0xb22c, TB,      RRE,   Z,   0, r2_o, 0, 0, testblock, 0)
>>  /* TEST PROTECTION */
>>      C(0xe501, TPROT,   SSE,   Z,   la1, a2, 0, 0, tprot, 0)
>>  
>> diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
>> index f6e5bce..de0ecd4 100644
>> --- a/target/s390x/mem_helper.c
>> +++ b/target/s390x/mem_helper.c
>> @@ -20,6 +20,7 @@
>>  
>>  #include "qemu/osdep.h"
>>  #include "cpu.h"
>> +#include "exec/address-spaces.h"
>>  #include "exec/helper-proto.h"
>>  #include "exec/exec-all.h"
>>  #include "exec/cpu_ldst.h"
>> @@ -973,6 +974,33 @@ void HELPER(stctl)(CPUS390XState *env, uint32_t r1, 
>> uint64_t a2, uint32_t r3)
>>      }
>>  }
>>  
>> +uint32_t HELPER(testblock)(CPUS390XState *env, uint64_t real_addr)
>> +{
>> +    CPUState *cs = CPU(s390_env_get_cpu(env));
>> +    uint64_t abs_addr;
>> +    int i;
>> +
>> +    real_addr = fix_address(env, real_addr);
>> +    abs_addr = mmu_real2abs(env, real_addr) & TARGET_PAGE_MASK;
>> +    if (!address_space_access_valid(&address_space_memory, abs_addr,
>> +                                    TARGET_PAGE_SIZE, true)) {
>> +        program_interrupt(env, PGM_ADDRESSING, 4);
>> +        return 1;
>> +    }
>> +
>> +    /* Check low-address protection */
>> +    if ((env->cregs[0] & CR0_LOWPROT) != 0 && real_addr < 0x2000) {
>> +        program_interrupt(env, PGM_PROTECTION, 4);
>> +        return 1;
>> +    }
>> +
>> +    for (i = 0; i < TARGET_PAGE_SIZE; i += 8) {
>> +        stq_phys(cs->as, abs_addr + i, 0);
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>>  uint32_t HELPER(tprot)(uint64_t a1, uint64_t a2)
>>  {
>>      /* XXX implement */
>> diff --git a/target/s390x/mmu_helper.c b/target/s390x/mmu_helper.c
>> index b11a027..31eb9ef 100644
>> --- a/target/s390x/mmu_helper.c
>> +++ b/target/s390x/mmu_helper.c
>> @@ -108,7 +108,7 @@ static void trigger_page_fault(CPUS390XState *env, 
>> target_ulong vaddr,
>>   * Translate real address to absolute (= physical)
>>   * address by taking care of the prefix mapping.
>>   */
>> -static target_ulong mmu_real2abs(CPUS390XState *env, target_ulong raddr)
>> +target_ulong mmu_real2abs(CPUS390XState *env, target_ulong raddr)
>>  {
>>      if (raddr < 0x2000) {
>>          return raddr + env->psa;    /* Map the lowcore. */
>> diff --git a/target/s390x/translate.c b/target/s390x/translate.c
>> index 4c48c59..61aa2c9 100644
>> --- a/target/s390x/translate.c
>> +++ b/target/s390x/translate.c
>> @@ -4057,6 +4057,15 @@ static ExitStatus op_tcxb(DisasContext *s, DisasOps 
>> *o)
>>  }
>>  
>>  #ifndef CONFIG_USER_ONLY
>> +
>> +static ExitStatus op_testblock(DisasContext *s, DisasOps *o)
>> +{
>> +    check_privileged(s);
> 
> You should also call potential_page_fault as the helper can trigger an
> exception.

Right, that makes sense now, too.

I'll send a v3 ...

Thanks!

 Thomas