Re: [Qemu-devel] [PATCH v2 08/16] postcopy: Plumb pagesize down into place helpers

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Laurent Vivier (lvivier@redhat.com) wrote:
> On 06/02/2017 18:32, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > 
> > Now we deal with normal size pages and huge pages we need
> > to tell the place handlers the size we're dealing with
> > and make sure the temporary page is large enough.
> > 
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >  include/migration/postcopy-ram.h |  6 +++--
> >  migration/postcopy-ram.c         | 47 ++++++++++++++++++++++++----------------
> >  migration/ram.c                  | 15 +++++++------
> >  3 files changed, 40 insertions(+), 28 deletions(-)
> > 
> > diff --git a/include/migration/postcopy-ram.h b/include/migration/postcopy-ram.h
> > index 43bbbca..8e036b9 100644
> > --- a/include/migration/postcopy-ram.h
> > +++ b/include/migration/postcopy-ram.h
> > @@ -74,13 +74,15 @@ void postcopy_discard_send_finish(MigrationState *ms,
> >   *    to use other postcopy_ routines to allocate.
> >   * returns 0 on success
> >   */
> > -int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from);
> > +int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
> > +                        size_t pagesize);
> >  
> >  /*
> >   * Place a zero page at (host) atomically
> >   * returns 0 on success
> >   */
> > -int postcopy_place_page_zero(MigrationIncomingState *mis, void *host);
> > +int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
> > +                             size_t pagesize);
> >  
> >  /*
> >   * Allocate a page of memory that can be mapped at a later point in time
> > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> > index 1e3d22f..a8b7fed 100644
> > --- a/migration/postcopy-ram.c
> > +++ b/migration/postcopy-ram.c
> > @@ -321,7 +321,7 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
> >      migrate_send_rp_shut(mis, qemu_file_get_error(mis->from_src_file) != 0);
> >  
> >      if (mis->postcopy_tmp_page) {
> > -        munmap(mis->postcopy_tmp_page, getpagesize());
> > +        munmap(mis->postcopy_tmp_page, mis->largest_page_size);
> >          mis->postcopy_tmp_page = NULL;
> >      }
> >      trace_postcopy_ram_incoming_cleanup_exit();
> > @@ -543,13 +543,14 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis)
> >   * Place a host page (from) at (host) atomically
> >   * returns 0 on success
> >   */
> > -int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
> > +int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
> > +                        size_t pagesize)
> >  {
> >      struct uffdio_copy copy_struct;
> >  
> >      copy_struct.dst = (uint64_t)(uintptr_t)host;
> >      copy_struct.src = (uint64_t)(uintptr_t)from;
> > -    copy_struct.len = getpagesize();
> > +    copy_struct.len = pagesize;
> >      copy_struct.mode = 0;
> >  
> >      /* copy also acks to the kernel waking the stalled thread up
> > @@ -559,8 +560,8 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
> >       */
> >      if (ioctl(mis->userfault_fd, UFFDIO_COPY, &copy_struct)) {
> >          int e = errno;
> > -        error_report("%s: %s copy host: %p from: %p",
> > -                     __func__, strerror(e), host, from);
> > +        error_report("%s: %s copy host: %p from: %p (size: %zd)",
> > +                     __func__, strerror(e), host, from, pagesize);
> >  
> >          return -e;
> >      }
> > @@ -573,23 +574,29 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
> >   * Place a zero page at (host) atomically
> >   * returns 0 on success
> >   */
> > -int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)
> > +int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
> > +                             size_t pagesize)
> >  {
> > -    struct uffdio_zeropage zero_struct;
> > +    trace_postcopy_place_page_zero(host);
> >  
> > -    zero_struct.range.start = (uint64_t)(uintptr_t)host;
> > -    zero_struct.range.len = getpagesize();
> > -    zero_struct.mode = 0;
> > +    if (pagesize == getpagesize()) {
> > +        struct uffdio_zeropage zero_struct;
> > +        zero_struct.range.start = (uint64_t)(uintptr_t)host;
> > +        zero_struct.range.len = getpagesize();
> > +        zero_struct.mode = 0;
> >  
> > -    if (ioctl(mis->userfault_fd, UFFDIO_ZEROPAGE, &zero_struct)) {
> > -        int e = errno;
> > -        error_report("%s: %s zero host: %p",
> > -                     __func__, strerror(e), host);
> > +        if (ioctl(mis->userfault_fd, UFFDIO_ZEROPAGE, &zero_struct)) {
> > +            int e = errno;
> > +            error_report("%s: %s zero host: %p",
> > +                         __func__, strerror(e), host);
> >  
> > -        return -e;
> > +            return -e;
> > +        }
> > +    } else {
> > +        /* TODO: The kernel can't use UFFDIO_ZEROPAGE for hugepages */
> > +        assert(0);
> >      }
> >  
> > -    trace_postcopy_place_page_zero(host);
> >      return 0;
> >  }
> >  
> > @@ -604,7 +611,7 @@ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)
> >  void *postcopy_get_tmp_page(MigrationIncomingState *mis)
> >  {
> >      if (!mis->postcopy_tmp_page) {
> > -        mis->postcopy_tmp_page = mmap(NULL, getpagesize(),
> > +        mis->postcopy_tmp_page = mmap(NULL, mis->largest_page_size,
> >                               PROT_READ | PROT_WRITE, MAP_PRIVATE |
> >                               MAP_ANONYMOUS, -1, 0);
> >          if (mis->postcopy_tmp_page == MAP_FAILED) {
> > @@ -649,13 +656,15 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis)
> >      return -1;
> >  }
> >  
> > -int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
> > +int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
> > +                        size_t pagesize)
> >  {
> >      assert(0);
> >      return -1;
> >  }
> >  
> > -int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)
> > +int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
> > +                        size_t pagesize)
> >  {
> >      assert(0);
> >      return -1;
> > diff --git a/migration/ram.c b/migration/ram.c
> > index 136996a..ff448ef 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -2354,6 +2354,7 @@ static int ram_load_postcopy(QEMUFile *f)
> >          void *host = NULL;
> >          void *page_buffer = NULL;
> >          void *place_source = NULL;
> > +        RAMBlock *block = NULL;
> >          uint8_t ch;
> >  
> >          addr = qemu_get_be64(f);
> > @@ -2363,7 +2364,7 @@ static int ram_load_postcopy(QEMUFile *f)
> >          trace_ram_load_postcopy_loop((uint64_t)addr, flags);
> >          place_needed = false;
> >          if (flags & (RAM_SAVE_FLAG_COMPRESS | RAM_SAVE_FLAG_PAGE)) {
> > -            RAMBlock *block = ram_block_from_stream(f, flags);
> > +            block = ram_block_from_stream(f, flags);
> >  
> >              host = host_from_ram_block_offset(block, addr);
> >              if (!host) {
> > @@ -2438,14 +2439,14 @@ static int ram_load_postcopy(QEMUFile *f)
> >  
> >          if (place_needed) {
> >              /* This gets called at the last target page in the host page */
> > +            void *place_dest = host + TARGET_PAGE_SIZE - block->page_size;
> > +
> >              if (all_zero) {
> > -                ret = postcopy_place_page_zero(mis,
> > -                                               host + TARGET_PAGE_SIZE -
> > -                                               qemu_host_page_size);
> > +                ret = postcopy_place_page_zero(mis, place_dest,
> > +                                               block->page_size);
> >              } else {
> > -                ret = postcopy_place_page(mis, host + TARGET_PAGE_SIZE -
> > -                                               qemu_host_page_size,
> > -                                               place_source);
> > +                ret = postcopy_place_page(mis, place_dest,
> > +                                          place_source, block->page_size);
> >              }
> >          }
> >          if (!ret) {
> > 
> 
> I think the "postcopy_tmp_page" part should be better in PATCH 07/16, so
> we know why you introduce the largest_page_size field, and this avoids
> to mix two kinds of change in this one (to place page and adjust tmp_page).

Well I did mention it in the commit message at the top of 7.

> Anyway:
> Reviewed-by: Laurent Vivier <lvivier@redhat.com>

Thanks

Dave
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK