* Peter Xu (pet...@redhat.com) wrote:
> On Wed, Jun 28, 2017 at 08:00:23PM +0100, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
> >
> > Use the recently added migration flag to hold whether
> > each RAMBlock has the UFFDIO_ZEROPAGE capability, use it
> > when it's available.
> >
> > This allows the use of postcopy on tmpfs as well as hugepage
> > backed files.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> > ---
> > migration/migration.h | 4 ++++
> > migration/postcopy-ram.c | 12 +++++++++---
> > 2 files changed, 13 insertions(+), 3 deletions(-)
> >
> > diff --git a/migration/migration.h b/migration/migration.h
> > index d9a268a3af..d109635d08 100644
> > --- a/migration/migration.h
> > +++ b/migration/migration.h
> > @@ -20,6 +20,10 @@
> > #include "exec/cpu-common.h"
> > #include "qemu/coroutine_int.h"
> >
> > +/* Migration flags to be set using qemu_ram_set_migration_flags */
> > +/* Postcopy can atomically zero pages in this RAMBlock */
> > +#define QEMU_MIGFLAG_POSTCOPY_ZERO 0x00000001
> > +
> > /* State for the incoming migration */
> > struct MigrationIncomingState {
> > QEMUFile *from_src_file;
> > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> > index be2a8f8e02..96338a8070 100644
> > --- a/migration/postcopy-ram.c
> > +++ b/migration/postcopy-ram.c
> > @@ -408,6 +408,12 @@ static int ram_block_enable_notify(const char
> > *block_name, void *host_addr,
> > error_report("%s userfault: Region doesn't support COPY",
> > __func__);
> > return -1;
> > }
> > + if (reg_struct.ioctls & ((__u64)1 << _UFFDIO_ZEROPAGE)) {
> > + RAMBlock *rb = qemu_ram_block_by_name(block_name);
> > + qemu_ram_set_migration_flags(rb, qemu_ram_get_migration_flags(rb) |
> > + QEMU_MIGFLAG_POSTCOPY_ZERO);
>
> Shall we use atomic_or() inside qemu_ram_set_migration_flags()? Then
> no need to fetch, and we'll be thread safe as well?
I've changed it to a simple |= in the new qemu_ram_set_uf_zeroable
that works on the rb->flags field.
> > + }
> > +
> >
> > return 0;
> > }
> > @@ -620,11 +626,11 @@ int postcopy_place_page(MigrationIncomingState *mis,
> > void *host, void *from,
> > int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
> > RAMBlock *rb)
> > {
> > + size_t pagesize = qemu_ram_pagesize(rb);
> > trace_postcopy_place_page_zero(host);
> >
> > - if (qemu_ram_pagesize(rb) == getpagesize()) {
> > - if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL,
> > getpagesize(),
> > - rb)) {
> > + if (qemu_ram_get_migration_flags(rb) & QEMU_MIGFLAG_POSTCOPY_ZERO) {
>
> IIUC, _UFFDIO_ZEROPAGE is not supported on huge pages. If so, would
> here worth a comment?
Added.
Dave
> > + if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, pagesize,
> > rb)) {
> > int e = errno;
> > error_report("%s: %s zero host: %p",
> > __func__, strerror(e), host);
> > --
> > 2.13.0
> >
>
> Thanks,
>
> --
> Peter Xu
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
