Re: [PATCH v6 13/18] s390x: protvirt: Disable address checks for PV guest IO emulation

[Janosch Frank]

On 3/4/20 6:55 PM, David Hildenbrand wrote:
> On 04.03.20 12:42, 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>
>> Reviewed-by: Thomas Huth <address@hidden>
>> ---
>>  target/s390x/ioinst.c | 26 +++++++++++++++++++-------
>>  1 file changed, 19 insertions(+), 7 deletions(-)
>>
>> diff --git a/target/s390x/ioinst.c b/target/s390x/ioinst.c
>> index c437a1d8c6..e4102430aa 100644
>> --- a/target/s390x/ioinst.c
>> +++ b/target/s390x/ioinst.c
>> @@ -17,6 +17,16 @@
>>  #include "trace.h"
>>  #include "hw/s390x/s390-pci-bus.h"
>>  
>> +static uint64_t get_address_from_regs(CPUS390XState *env, uint32_t ipb,
>> +                                      uint8_t *ar)
>> +{
> 
> Please add a comment here why this is done. (e.g., make all address
> checks - like alignment checks - in the caller succeed, and we don't
> need the address).

     * Addresses for protected guests are all offsets into the


     * satellite block which holds the IO control structures. Those


     * control structures are always aligned and accessible, so we can


     * return 0 here which will pass the following address checks.

?

> 
>> +    if (env->pv) {
>> +        *ar = 0;
>> +        return 0;
>> +    }
>> +    return decode_basedisp_s(env, ipb, ar);
>> +}
>> +
> 
> Reviewed-by: David Hildenbrand <address@hidden>
> 
>

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