Re: [RFC PATCH] KVM: PPC: Book3S HV: add support for page faults in VM_IO|VM_PFNMAP vmas

["Cédric Le Goater" <clg@kaod.org>]

On 02/08/2018 11:19 PM, Benjamin Herrenschmidt wrote:
> On Thu, 2018-02-08 at 17:03 +0100, Cédric Le Goater wrote:
>>  
>> +/*
>> + * Stolen from virt/kvm/kvm_main.c
>> + */
> 
> Just export it. It's annoying that we can't just ues hva_to_pfn() ...

yes. I might add a kvm_ prefix. I will check to see what is the
best pratice.

[ ... ]

>> @@ -402,8 +450,15 @@ int kvmppc_book3s_radix_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
>>                 vma = find_vma(current->mm, hva);
>>                 if (vma && vma->vm_start <= hva && hva < vma->vm_end &&
>>                     (vma->vm_flags & VM_PFNMAP)) {
>> -                       pfn = vma->vm_pgoff +
>> -                               ((hva - vma->vm_start) >> PAGE_SHIFT);
>> +                       if (vma->vm_flags & (VM_IO | VM_PFNMAP)) {
>> +                               ret = hva_to_pfn_remapped(vma, hva, writing,
>> +                                                         &pfn);
>> +                               if (ret == -EAGAIN)
>> +                                       return RESUME_GUEST;
>> +                       } else {
>> +                               pfn = vma->vm_pgoff +
>> +                                       ((hva - vma->vm_start) >> PAGE_SHIFT);
>> +                       }
> 
> I don't think the else case is useful. If fact you are checking
> VM_PFNMAP twice...

yes. I am not sure what the VM_PFNMAP case does. The code comes 
from kvmppc_book3s_hv_page_fault() I suppose.

Thanks,

C.