Re: [PATCH] s390x/pv: Retry ioctls on -EINTR

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 27.03.20 10:49, David Hildenbrand wrote:
> On 27.03.20 10:43, Christian Borntraeger wrote:
>> PV_ENABLE (and maybe others) might return -EINTR when a signal is
>> pending. Let us retry the ioctl in that case.
>>
>> Fixes: 4d226deafc44 ("s390x: protvirt: Support unpack facility")
>> Reported-by: Marc Hartmayer <mhartmay@linux.ibm.com>
>> Tested-by: Marc Hartmayer <mhartmay@linux.ibm.com>
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> ---
>>  hw/s390x/pv.c | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/s390x/pv.c b/hw/s390x/pv.c
>> index 8cf5cd2c9b..2758b02c96 100644
>> --- a/hw/s390x/pv.c
>> +++ b/hw/s390x/pv.c
>> @@ -23,7 +23,11 @@ static int __s390_pv_cmd(uint32_t cmd, const char *cmdname, void *data)
>>          .cmd = cmd,
>>          .data = (uint64_t)data,
>>      };
>> -    int rc = kvm_vm_ioctl(kvm_state, KVM_S390_PV_COMMAND, &pv_cmd);
>> +    int rc;
>> +
>> +    do {
>> +        rc  = kvm_vm_ioctl(kvm_state, KVM_S390_PV_COMMAND, &pv_cmd);
>> +    } while (rc == -EINTR);
>>  
>>      if (rc) {
>>          error_report("KVM PV command %d (%s) failed: header rc %x rrc %x "
>>
> 
> I fail to see where that is triggered in the kernel.
> 
> t480s: ~/git/linux/arch/s390/kvm (HEAD losgelöst bei next/master) $ git
> grep "EINTR"
> kvm-s390.c:     if (exit_reason == -EINTR) {
> kvm-s390.c:             return -EINTR;
> kvm-s390.c:             rc = -EINTR;
> vsie.c: if (rc == -EINTR) {
> 
> 
> Can you help me out? Is that documented?

It is related to the kernel patch.
ksm_madvise->unmerge_ksm_pages has

                if (signal_pending(current))
                        err = -ERESTARTSYS;


entry.S will retranslate ERESTARTSYS into -EINTR.