* Jagannathan Raman (jag.ra...@oracle.com) wrote: > In some cases, for example MMIO read, QEMU has to wait for the remote to > complete a command before proceeding. An eventfd based mechanism is > added to synchronize QEMU & remote process. > > Signed-off-by: John G Johnson <john.g.john...@oracle.com> > Signed-off-by: Jagannathan Raman <jag.ra...@oracle.com> > Signed-off-by: Elena Ufimtseva <elena.ufimts...@oracle.com> > --- > include/io/mpqemu-link.h | 7 +++++++ > io/mpqemu-link.c | 41 +++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 48 insertions(+) > > diff --git a/include/io/mpqemu-link.h b/include/io/mpqemu-link.h > index 2f2dd83..ae04fca 100644 > --- a/include/io/mpqemu-link.h > +++ b/include/io/mpqemu-link.h > @@ -135,4 +135,11 @@ void mpqemu_link_set_callback(MPQemuLinkState *s, > mpqemu_link_callback callback); > void mpqemu_start_coms(MPQemuLinkState *s); > > +#define GET_REMOTE_WAIT eventfd(0, EFD_CLOEXEC) > +#define PUT_REMOTE_WAIT(wait) close(wait) > +#define PROXY_LINK_WAIT_DONE 1 > + > +uint64_t wait_for_remote(int efd); > +void notify_proxy(int fd, uint64_t val); > + > #endif > diff --git a/io/mpqemu-link.c b/io/mpqemu-link.c > index bac120b..73b7032 100644 > --- a/io/mpqemu-link.c > +++ b/io/mpqemu-link.c > @@ -10,6 +10,7 @@ > > #include "qemu/osdep.h" > #include "qemu-common.h" > +#include <poll.h> > > #include "qemu/module.h" > #include "io/mpqemu-link.h" > @@ -216,6 +217,46 @@ int mpqemu_msg_recv(MPQemuMsg *msg, MPQemuChannel *chan) > return rc; > } > > +uint64_t wait_for_remote(int efd) > +{ > + struct pollfd pfd = { .fd = efd, .events = POLLIN }; > + uint64_t val; > + int ret; > + > + ret = poll(&pfd, 1, 1000); > + > + switch (ret) { > + case 0: > + qemu_log_mask(LOG_REMOTE_DEBUG, "Error wait_for_remote: Timed > out\n"); > + /* TODO: Kick-off error recovery */ > + return ULLONG_MAX;
Shouldn't these be UINT64_MAX? > + case -1: > + qemu_log_mask(LOG_REMOTE_DEBUG, "Poll error wait_for_remote: %s\n", > + strerror(errno)); > + return ULLONG_MAX; > + default: > + if (read(efd, &val, sizeof(val)) == -1) { > + qemu_log_mask(LOG_REMOTE_DEBUG, "Error wait_for_remote: %s\n", > + strerror(errno)); > + return ULLONG_MAX; > + } > + } > + > + val = (val == ULLONG_MAX) ? val : (val - 1); Can you explain what's going on there?? > + return val; > +} > + > +void notify_proxy(int efd, uint64_t val) > +{ > + val = (val == ULLONG_MAX) ? val : (val + 1); > + > + if (write(efd, &val, sizeof(val)) == -1) { I'd actually check the write/read's are returning sizeof(val) - they can on a bad day return 0 or send only a few bytes; in theory? Dave > + qemu_log_mask(LOG_REMOTE_DEBUG, "Error notify_proxy: %s\n", > + strerror(errno)); > + } > +} > + > static gboolean mpqemu_link_handler_prepare(GSource *gsrc, gint *timeout) > { > g_assert(timeout); > -- > 1.8.3.1 > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK