On 13.12.2017 12:46, David Hildenbrand wrote:
> On 13.12.2017 12:44, Roman Kagan wrote:
>> On Wed, Dec 13, 2017 at 10:55:02AM +0100, David Hildenbrand wrote:
>>>
>>>> +static u16 kvm_hvcall_signal_event(struct kvm_vcpu *vcpu, bool fast, u64 param)
>>>> +{
>>>> + u16 ret;
>>>> + u32 conn_id, flag_no;
>>>> + int idx;
>>>> + struct eventfd_ctx *eventfd;
>>>> +
>>>> + if (unlikely(!fast)) {
>>>> + gpa_t gpa = param;
>>>> +
>>>> + if ((gpa & (__alignof__(param) - 1)) ||
>>>> + offset_in_page(gpa) + sizeof(param) > PAGE_SIZE)
>>>> + return HV_STATUS_INVALID_ALIGNMENT;
>>>> +
>>>> + idx = srcu_read_lock(&vcpu->kvm->srcu);
>>>> + ret = kvm_vcpu_read_guest(vcpu, gpa, ¶m, sizeof(param));
>>>> + srcu_read_unlock(&vcpu->kvm->srcu, idx);
>>>> +
>>>> + if (ret < 0)
>>>> + return HV_STATUS_INSUFFICIENT_MEMORY;
>>>
>>> "... event flags do not require any buffer allocation or queuing within
>>> the hypervisor, so HvSignalEvent will never fail due to insufficient
>>> resources."
>>
>> Ouch. I wonder what else to map -EFAULT to then... Looks like
>> HV_STATUS_INVALID_ALIGNMENT is the most appropriate (as in "The input or
>> output GPA pointer is not within the bounds of the GPA space.")
>>
>> Thanks,
>> Roman.
>>
>
> It is likely happen rearelyn, but usually if we are out of memory we
> should report to user space. (chances that we won't be able to continue
> for longer either way are very high)
>
(I implied -ENOMEM is translated to -EFAULT) it can of course happen if
the address is wrong.
Also wonder how to deal with that. Could it be that we even have to
trigger a page fault in the guest?
--
Thanks,
David / dhildenb
