Re: [PATCH 14/15] s390x: protvirt: Disable address checks for PV guest IO emulation

[Thomas Huth]

On 28/11/2019 17.10, Janosch Frank wrote:
> On 11/28/19 4:28 PM, Thomas Huth wrote:
>> On 20/11/2019 12.43, Janosch Frank wrote:
>>> IO instruction data is routed through SIDAD for protected guests, so
>>> adresses do not need to be checked, as this is kernel memory.
>>>
>>> Signed-off-by: Janosch Frank <address@hidden>
>>> ---
>>>  target/s390x/ioinst.c | 46 +++++++++++++++++++++++++++----------------
>>>  1 file changed, 29 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/target/s390x/ioinst.c b/target/s390x/ioinst.c
>>> index c437a1d8c6..d3bd422ddd 100644
>>> --- a/target/s390x/ioinst.c
>>> +++ b/target/s390x/ioinst.c
>>> @@ -110,11 +110,13 @@ void ioinst_handle_msch(S390CPU *cpu, uint64_t reg1, 
>>> uint32_t ipb, uintptr_t ra)
>>>      int cssid, ssid, schid, m;
>>>      SubchDev *sch;
>>>      SCHIB schib;
>>> -    uint64_t addr;
>>> +    uint64_t addr = 0;
>>>      CPUS390XState *env = &cpu->env;
>>> -    uint8_t ar;
>>> +    uint8_t ar = 0;
>>>  
>>> -    addr = decode_basedisp_s(env, ipb, &ar);
>>> +    if (!env->pv) {
>>> +        addr = decode_basedisp_s(env, ipb, &ar);
>>> +    }
>>>      if (addr & 3) {
>>>          s390_program_interrupt(env, PGM_SPECIFICATION, ra);
>>>          return;
>>> @@ -167,11 +169,13 @@ void ioinst_handle_ssch(S390CPU *cpu, uint64_t reg1, 
>>> uint32_t ipb, uintptr_t ra)
>>>      int cssid, ssid, schid, m;
>>>      SubchDev *sch;
>>>      ORB orig_orb, orb;
>>> -    uint64_t addr;
>>> +    uint64_t addr = 0;
>>>      CPUS390XState *env = &cpu->env;
>>> -    uint8_t ar;
>>> +    uint8_t ar = 0;
>>>  
>>> -    addr = decode_basedisp_s(env, ipb, &ar);
>>> +    if (!env->pv) {
>>> +        addr = decode_basedisp_s(env, ipb, &ar);
>>> +    }
>>>      if (addr & 3) {
>>>          s390_program_interrupt(env, PGM_SPECIFICATION, ra);
>>>          return;
>>> @@ -198,12 +202,14 @@ void ioinst_handle_ssch(S390CPU *cpu, uint64_t reg1, 
>>> uint32_t ipb, uintptr_t ra)
>>>  void ioinst_handle_stcrw(S390CPU *cpu, uint32_t ipb, uintptr_t ra)
>>>  {
>>>      CRW crw;
>>> -    uint64_t addr;
>>> +    uint64_t addr = 0;
>>>      int cc;
>>>      CPUS390XState *env = &cpu->env;
>>> -    uint8_t ar;
>>> +    uint8_t ar = 0;
>>>  
>>> -    addr = decode_basedisp_s(env, ipb, &ar);
>>> +    if (!env->pv) {
>>> +        addr = decode_basedisp_s(env, ipb, &ar);
>>> +    }
>>>      if (addr & 3) {
>>>          s390_program_interrupt(env, PGM_SPECIFICATION, ra);
>>>          return;
>>> @@ -228,13 +234,15 @@ void ioinst_handle_stsch(S390CPU *cpu, uint64_t reg1, 
>>> uint32_t ipb,
>>>  {
>>>      int cssid, ssid, schid, m;
>>>      SubchDev *sch;
>>> -    uint64_t addr;
>>> +    uint64_t addr = 0;
>>>      int cc;
>>>      SCHIB schib;
>>>      CPUS390XState *env = &cpu->env;
>>> -    uint8_t ar;
>>> +    uint8_t ar = 0;
>>>  
>>> -    addr = decode_basedisp_s(env, ipb, &ar);
>>> +    if (!env->pv) {
>>> +        addr = decode_basedisp_s(env, ipb, &ar);
>>> +    }
>>>      if (addr & 3) {
>>>          s390_program_interrupt(env, PGM_SPECIFICATION, ra);
>>>          return;
>>> @@ -294,16 +302,18 @@ int ioinst_handle_tsch(S390CPU *cpu, uint64_t reg1, 
>>> uint32_t ipb, uintptr_t ra)
>>>      int cssid, ssid, schid, m;
>>>      SubchDev *sch;
>>>      IRB irb;
>>> -    uint64_t addr;
>>> +    uint64_t addr = 0;
>>>      int cc, irb_len;
>>> -    uint8_t ar;
>>> +    uint8_t ar = 0;
>>>  
>>>      if (ioinst_disassemble_sch_ident(reg1, &m, &cssid, &ssid, &schid)) {
>>>          s390_program_interrupt(env, PGM_OPERAND, ra);
>>>          return -EIO;
>>>      }
>>>      trace_ioinst_sch_id("tsch", cssid, ssid, schid);
>>> -    addr = decode_basedisp_s(env, ipb, &ar);
>>> +    if (!env->pv) {
>>> +        addr = decode_basedisp_s(env, ipb, &ar);
>>> +    }
>>>      if (addr & 3) {
>>>          s390_program_interrupt(env, PGM_SPECIFICATION, ra);
>>>          return -EIO;
>>
>> Would it make sense to hide all these changes in decode_basedisp_s()
>> instead? ... so that decode_basedisp_s() returns 0 if env->pv == true ?
>> ... or are there still cases where we need real values from
>> decode_basedisp_s() in case of env->pv==true?
> 
> I'd like to keep decode_basedisp_s() as is, but how about a static
> function in ioinst.c called something like get_address_from_regs()?
> 
> It'll call decode_basedisp_s() or return 0.

Sounds fine for me, too!

 Thomas

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