[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v4 15/18] xen/mem_sharing: VM forking
On Thu, Jan 9, 2020 at 8:34 AM Jan Beulich <jbeulich@xxxxxxxx> wrote: > > On 09.01.2020 16:10, Roger Pau Monné wrote: > > On Thu, Jan 09, 2020 at 06:41:12AM -0700, Tamas K Lengyel wrote: > >> On Thu, Jan 9, 2020 at 3:29 AM Julien Grall <julien@xxxxxxx> wrote: > >>> > >>> Hi Tamas, > >>> > >>> On 08/01/2020 17:14, Tamas K Lengyel wrote: > >>>> +static int mem_sharing_fork(struct domain *d, struct domain *cd) > >>>> +{ > >>>> + int rc; > >>>> + > >>>> + if ( !d->controller_pause_count && > >>>> + (rc = domain_pause_by_systemcontroller(d)) ) > >>> > >>> AFAIU, the parent domain will be paused if it wasn't paused before and > >>> this will not be unpaused by the same hypercall. Right? > >> > >> Yes, it needs to remain paused as long as there are forks active from > >> it. Afterwards it can be unpaused. > > > > If you want the parent domain to remain paused for as long as the > > forks are active, shouldn't each fork increment the pause count on > > creation and decrement it when the fork is destroyed? > > > > How can you assure no other operation or entity has incremented > > controller_pause_count temporary and is likely to decrement it at some > > point while forks are still active? > > The _by_systemcontroller variants look wrong to be used here anyway. > Why is this not simply domain_{,un}pause()? > My reasoning was that by default the user should pause the parent VM before forking. This sanity checks just mimicks that step in case the user didn't do that already. But I guess either would work, I don't really see much difference between the two. Tamas _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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