* Peter Xu (pet...@redhat.com) wrote:
> On Fri, Feb 16, 2018 at 01:16:13PM +0000, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
> >
> > Send requests back to the source for shared page requests.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> > ---
> > migration/migration.h | 2 ++
> > migration/postcopy-ram.c | 31 ++++++++++++++++++++++++++++---
> > migration/postcopy-ram.h | 3 +++
> > migration/trace-events | 2 ++
> > 4 files changed, 35 insertions(+), 3 deletions(-)
> >
> > diff --git a/migration/migration.h b/migration/migration.h
> > index d158e62cf2..457bf37ec2 100644
> > --- a/migration/migration.h
> > +++ b/migration/migration.h
> > @@ -46,6 +46,8 @@ struct MigrationIncomingState {
> > int userfault_quit_fd;
> > QEMUFile *to_src_file;
> > QemuMutex rp_mutex; /* We send replies from multiple threads */
> > + /* RAMBlock of last request sent to source */
> > + RAMBlock *last_rb;
> > void *postcopy_tmp_page;
> > void *postcopy_tmp_zero_page;
> > /* PostCopyFD's for external userfaultfds & handlers of shared memory
> > */
> > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> > index d118b78bf5..277ff749a0 100644
> > --- a/migration/postcopy-ram.c
> > +++ b/migration/postcopy-ram.c
> > @@ -534,6 +534,31 @@ static int ram_block_enable_notify(const char
> > *block_name, void *host_addr,
> > return 0;
> > }
> >
> > +/*
> > + * Callback from shared fault handlers to ask for a page,
> > + * the page must be specified by a RAMBlock and an offset in that rb
> > + */
> > +int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
> > + uint64_t client_addr, uint64_t rb_offset)
> > +{
> > + size_t pagesize = qemu_ram_pagesize(rb);
> > + uint64_t aligned_rbo = rb_offset & ~(pagesize - 1);
> > + MigrationIncomingState *mis = migration_incoming_get_current();
> > +
> > + trace_postcopy_request_shared_page(pcfd->idstr, qemu_ram_get_idstr(rb),
> > + rb_offset);
> > + /* TODO: Check bitmap to see if we already have the page */
> > + if (rb != mis->last_rb) {
> > + mis->last_rb = rb;
> > + migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb),
> > + aligned_rbo, pagesize);
> > + } else {
> > + /* Save some space */
> > + migrate_send_rp_req_pages(mis, NULL, aligned_rbo, pagesize);
> > + }
> > + return 0;
> > +}
> > +
>
> So IIUC this can only be called within the page fault thread or there
> can be race. Is there a way to guarantee this? Or do we need a
> comment for that?
I don't think there's a way to guarantee it - especially since it has
to be called by the device-specific shared handlers in another file -
I've updated the comment to:
/*
* Callback from shared fault handlers to ask for a page,
* the page must be specified by a RAMBlock and an offset in that rb
* Note: Only for use by shared fault handlers (in fault thread)
*/
Dave
> > /*
> > * Handle faults detected by the USERFAULT markings
> > */
> > @@ -544,9 +569,9 @@ static void *postcopy_ram_fault_thread(void *opaque)
> > int ret;
> > size_t index;
> > RAMBlock *rb = NULL;
> > - RAMBlock *last_rb = NULL; /* last RAMBlock we sent part of */
> >
> > trace_postcopy_ram_fault_thread_entry();
> > + mis->last_rb = NULL; /* last RAMBlock we sent part of */
> > qemu_sem_post(&mis->fault_thread_sem);
> >
> > struct pollfd *pfd;
> > @@ -634,8 +659,8 @@ static void *postcopy_ram_fault_thread(void *opaque)
> > * Send the request to the source - we want to request one
> > * of our host page sizes (which is >= TPS)
> > */
> > - if (rb != last_rb) {
> > - last_rb = rb;
> > + if (rb != mis->last_rb) {
> > + mis->last_rb = rb;
> > migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb),
> > rb_offset, qemu_ram_pagesize(rb));
> > } else {
> > diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
> > index dbc2ee1f2b..4c63f20df4 100644
> > --- a/migration/postcopy-ram.h
> > +++ b/migration/postcopy-ram.h
> > @@ -162,5 +162,8 @@ struct PostCopyFD {
> > */
> > void postcopy_register_shared_ufd(struct PostCopyFD *pcfd);
> > void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd);
> > +/* Callback from shared fault handlers to ask for a page */
> > +int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
> > + uint64_t client_addr, uint64_t offset);
> >
> > #endif
> > diff --git a/migration/trace-events b/migration/trace-events
> > index 1e617ad7a6..7c910b5479 100644
> > --- a/migration/trace-events
> > +++ b/migration/trace-events
> > @@ -198,6 +198,8 @@ postcopy_ram_incoming_cleanup_closeuf(void) ""
> > postcopy_ram_incoming_cleanup_entry(void) ""
> > postcopy_ram_incoming_cleanup_exit(void) ""
> > postcopy_ram_incoming_cleanup_join(void) ""
> > +postcopy_request_shared_page(const char *sharer, const char *rb, uint64_t
> > rb_offset) "for %s in %s offset 0x%"PRIx64
> > +
> > save_xbzrle_page_skipping(void) ""
> > save_xbzrle_page_overflow(void) ""
> > ram_save_iterate_big_wait(uint64_t milliconds, int iterations) "big wait:
> > %" PRIu64 " milliseconds, %d iterations"
> > --
> > 2.14.3
> >
>
> --
> Peter Xu
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
