[Xen-devel] -EINTR return in domain_relinquish_resources

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

As I was looking at some of the XSA I realized that the
call-chain of:

 domain_relinquish_resources
   ->vcpu_destroy_pagetables
     -> put_page_and_type_preemptible
        -> __put_page_type
                returns -EINTR

which means we end up at:
 618         rc = domain_relinquish_resources(d);                               
     
 619         if ( rc != 0 )                                                     
     
 620         {                                                                  
     
 621             if ( rc == -ERESTART )                                         
     
 622                 rc = -EAGAIN;                                              
     
 623             break;             <=== with rc=-EINTR
 624         }                                         

And return -EINTR to user-space - which loop in 
'xc_domain_destroy' is only looking for:

 112 int xc_domain_destroy(xc_interface *xch,                                   
     
 113                       uint32_t domid)                                      
     
 114 {                                                                          
     
 115     int ret;                                                               
     
 116     DECLARE_DOMCTL;                                                        
     
 117     domctl.cmd = XEN_DOMCTL_destroydomain;                                 
     
 118     domctl.domain = (domid_t)domid;                                        
     
 119     do {                                                                   
     
 120         ret = do_domctl(xch, &domctl);                                     
     
 121     } while ( ret && (errno == EAGAIN) );                                  
     
 122     return ret;                                                            
     
 123 }                                

which to my reading looks like we would exit out and leave
an DOMDYING_dying domain. Looking at the code it seems possible
to continue on if the user does 'xl destroy <X>' guest again,
but I was wondering if:

 a). Should the toolstack (libxl or libxc) have the code to
     handle -EINTR?

 b). Or should the hypervisor convert the -EINTR to -ERESTART
     (or -EAGAIN) - which most of the code (see users of
     get_page_type_preemptible) do right now?

Thanks!

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