On 11/21/2017 04:18 PM, David Hildenbrand wrote:
> On 21.11.2017 16:08, Christian Borntraeger wrote:
>> Old kernels did not check for zero in the irq_state.flags field and old
>> QEMUs did not zero the flag field when calling KVM_S390_*_IRQ_STATE.
>> Let's add a comment and dummy code to prevent future usage of flags
>> and pad.
>>
>> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
>> ---
>> arch/s390/kvm/kvm-s390.c | 14 ++++++++++++++
>> 1 file changed, 14 insertions(+)
>>
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index 6a5e02f..1baa393 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -3834,6 +3834,16 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>> r = -EINVAL;
>> break;
>> }
>> + if (irq_state.flags) {
>
> I don't see the need for if (do I need more coffee?).
It is a dummy construct that matches other checks like "if flags return -EINVAL". But since
it is dummy we can do whatever we want (even just a comment) since nobody reads flags as of
today.
>
>> + /*
>> + * This is a placeholder to make sure that nobody uses
>> + * flags and pad. Old kernels did not check for zero
>> + * and old QEMUs did not zero the flag field.
>> + * That means that we cannot use the flags field for
>> + * any possible extension.
>> + */
>> + irq_state.flags = 0;
>> + }
>> r = kvm_s390_set_irq_state(vcpu,
>> (void __user *) irq_state.buf,
>> irq_state.len);
>> @@ -3849,6 +3859,10 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>> r = -EINVAL;
>> break;
>> }
>> + if (irq_state.flags) {
>
> dito
>
>> + /* see above */
>
> /* same handling as for kvm_s390_set_irq_state() */
>
>> + irq_state.flags = 0;
>> + }
>> r = kvm_s390_get_irq_state(vcpu,
>> (__u8 __user *) irq_state.buf,
>> irq_state.len);
>>
>
>
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