Re: [Qemu-devel] [PATCH V6 02/10] migration: pass MigrationIncomingState* into migration check functions

[Alexey Perevalov]

On 05/31/2017 08:54 PM, Dr. David Alan Gilbert wrote:
> * Alexey Perevalov (address@hidden) wrote:
> > That tiny refactoring is necessary to be able to set
> > UFFD_FEATURE_THREAD_ID while requesting features, and then
> > to create downtime context in case when kernel supports it.
> >
> > Signed-off-by: Alexey Perevalov <address@hidden>
> > ---
> >   migration/migration.c    |  2 +-
> >   migration/postcopy-ram.c | 10 +++++-----
> >   migration/postcopy-ram.h |  2 +-
> >   migration/savevm.c       |  2 +-
> >   4 files changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 0304c01..d735976 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -789,7 +789,7 @@ void 
> > qmp_migrate_set_capabilities(MigrationCapabilityStatusList *params,
> >            * special support.
> >            */
> >           if (!old_postcopy_cap && runstate_check(RUN_STATE_INMIGRATE) &&
> > -            !postcopy_ram_supported_by_host()) {
> > +            !postcopy_ram_supported_by_host(NULL)) {
> Why is that NULL rather than migration_incoming_get_current()?
> That's on the destination.
In current implementation, AFAIU,
migrate-set-capabilities with postcopy-ram argument should be done on 
source machine only,
and it's not required on destination. And it is unnecessary requirement 
to support userfaultfd on
source and check it there.

> Dave
>
> >               /* postcopy_ram_supported_by_host will have emitted a more
> >                * detailed message
> >                */
> > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> > index a0489f6..4adab36 100644
> > --- a/migration/postcopy-ram.c
> > +++ b/migration/postcopy-ram.c
> > @@ -59,7 +59,7 @@ struct PostcopyDiscardState {
> >   #include <sys/eventfd.h>
> >   #include <linux/userfaultfd.h>
> >   
> > -static bool ufd_version_check(int ufd)
> > +static bool ufd_version_check(int ufd, MigrationIncomingState *mis)
> >   {
> >       struct uffdio_api api_struct;
> >       uint64_t ioctl_mask;
> > @@ -112,7 +112,7 @@ static int test_range_shared(const char *block_name, void 
> > *host_addr,
> >    * normally fine since if the postcopy succeeds it gets turned back on at the
> >    * end.
> >    */
> > -bool postcopy_ram_supported_by_host(void)
> > +bool postcopy_ram_supported_by_host(MigrationIncomingState *mis)
> >   {
> >       long pagesize = getpagesize();
> >       int ufd = -1;
> > @@ -135,7 +135,7 @@ bool postcopy_ram_supported_by_host(void)
> >       }
> >   
> >       /* Version and features check */
> > -    if (!ufd_version_check(ufd)) {
> > +    if (!ufd_version_check(ufd, mis)) {
> >           goto out;
> >       }
> >   
> > @@ -512,7 +512,7 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis)
> >        * Although the host check already tested the API, we need to
> >        * do the check again as an ABI handshake on the new fd.
> >        */
> > -    if (!ufd_version_check(mis->userfault_fd)) {
> > +    if (!ufd_version_check(mis->userfault_fd, mis)) {
> >           return -1;
> >       }
> >   
> > @@ -650,7 +650,7 @@ void *postcopy_get_tmp_page(MigrationIncomingState *mis)
> >   
> >   #else
> >   /* No target OS support, stubs just fail */
> > -bool postcopy_ram_supported_by_host(void)
> > +bool postcopy_ram_supported_by_host(MigrationIncomingState *mis)
> >   {
> >       error_report("%s: No OS support", __func__);
> >       return false;
> > diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
> > index 52d51e8..587a8b8 100644
> > --- a/migration/postcopy-ram.h
> > +++ b/migration/postcopy-ram.h
> > @@ -14,7 +14,7 @@
> >   #define QEMU_POSTCOPY_RAM_H
> >   
> >   /* Return true if the host supports everything we need to do postcopy-ram */
> > -bool postcopy_ram_supported_by_host(void);
> > +bool postcopy_ram_supported_by_host(MigrationIncomingState *mis);
> >   
> >   /*
> >    * Make all of RAM sensitive to accesses to areas that haven't yet been 
> > written
> > diff --git a/migration/savevm.c b/migration/savevm.c
> > index f5e8194..61a6df7 100644
> > --- a/migration/savevm.c
> > +++ b/migration/savevm.c
> > @@ -1356,7 +1356,7 @@ static int 
> > loadvm_postcopy_handle_advise(MigrationIncomingState *mis)
> >           return -1;
> >       }
> >   
> > -    if (!postcopy_ram_supported_by_host()) {
> > +    if (!postcopy_ram_supported_by_host(mis)) {
> >           postcopy_state_set(POSTCOPY_INCOMING_NONE);
> >           return -1;
> >       }
> > --
> > 1.8.3.1
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK

--
Best regards,
Alexey Perevalov