[v4 4/5] KVM: PPC: Book3S HV: retry page migration before erroring-out

[Ram Pai]

I am dropping this patch based on our conversation, where we agreed, we
need to rootcause the migration failure.

On Thu, Jul 23, 2020 at 11:43:44AM +0530, Bharata B Rao wrote:
> On Fri, Jul 17, 2020 at 01:00:26AM -0700, Ram Pai wrote:
> > @@ -812,7 +842,7 @@ unsigned long kvmppc_h_svm_page_in(struct kvm *kvm, unsigned long gpa,
> >  	struct vm_area_struct *vma;
> >  	int srcu_idx;
> >  	unsigned long gfn = gpa >> page_shift;
> > -	int ret;
> > +	int ret, repeat_count = REPEAT_COUNT;
> >  
> >  	if (!(kvm->arch.secure_guest & KVMPPC_SECURE_INIT_START))
> >  		return H_UNSUPPORTED;
> > @@ -826,34 +856,44 @@ unsigned long kvmppc_h_svm_page_in(struct kvm *kvm, unsigned long gpa,
> >  	if (flags & H_PAGE_IN_SHARED)
> >  		return kvmppc_share_page(kvm, gpa, page_shift);
> >  
> > -	ret = H_PARAMETER;
> >  	srcu_idx = srcu_read_lock(&kvm->srcu);
> > -	mmap_read_lock(kvm->mm);
> >  
> > -	start = gfn_to_hva(kvm, gfn);
> > -	if (kvm_is_error_hva(start))
> > -		goto out;
> > -
> > -	mutex_lock(&kvm->arch.uvmem_lock);
> >  	/* Fail the page-in request of an already paged-in page */
> > -	if (kvmppc_gfn_is_uvmem_pfn(gfn, kvm, NULL))
> > -		goto out_unlock;
> > +	mutex_lock(&kvm->arch.uvmem_lock);
> > +	ret = kvmppc_gfn_is_uvmem_pfn(gfn, kvm, NULL);
> > +	mutex_unlock(&kvm->arch.uvmem_lock);
> 
> Same comment as for the prev patch. I don't think you can release
> the lock here.
> 
> > +	if (ret) {
> > +		srcu_read_unlock(&kvm->srcu, srcu_idx);
> > +		return H_PARAMETER;
> > +	}
> >  
> > -	end = start + (1UL << page_shift);
> > -	vma = find_vma_intersection(kvm->mm, start, end);
> > -	if (!vma || vma->vm_start > start || vma->vm_end < end)
> > -		goto out_unlock;
> > +	do {
> > +		ret = H_PARAMETER;
> > +		mmap_read_lock(kvm->mm);
> >  
> > -	if (kvmppc_svm_migrate_page(vma, start, end, gpa, kvm, page_shift,
> > -				true))
> > -		goto out_unlock;
> > +		start = gfn_to_hva(kvm, gfn);
> > +		if (kvm_is_error_hva(start)) {
> > +			mmap_read_unlock(kvm->mm);
> > +			break;
> > +		}
> >  
> > -	ret = H_SUCCESS;
> > +		end = start + (1UL << page_shift);
> > +		vma = find_vma_intersection(kvm->mm, start, end);
> > +		if (!vma || vma->vm_start > start || vma->vm_end < end) {
> > +			mmap_read_unlock(kvm->mm);
> > +			break;
> > +		}
> > +
> > +		mutex_lock(&kvm->arch.uvmem_lock);
> > +		ret = kvmppc_svm_migrate_page(vma, start, end, gpa, kvm, page_shift, true);
> > +		mutex_unlock(&kvm->arch.uvmem_lock);
> > +
> > +		mmap_read_unlock(kvm->mm);
> > +	} while (ret == -2 && repeat_count--);
> > +
> > +	if (ret == -2)
> > +		ret = H_BUSY;
> >  
> > -out_unlock:
> > -	mutex_unlock(&kvm->arch.uvmem_lock);
> > -out:
> > -	mmap_read_unlock(kvm->mm);
> >  	srcu_read_unlock(&kvm->srcu, srcu_idx);
> >  	return ret;
> >  }
> > -- 
> > 1.8.3.1

-- 
Ram Pai