Override hook_ram_load to receive the pipe file descriptor passed by source process and page address which will be extracted to vmsplice the page data from pipe.
Signed-off-by: Lei Li <li...@linux.vnet.ibm.com> --- migration-local.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 55 insertions(+), 0 deletions(-) diff --git a/migration-local.c b/migration-local.c index 14207e9..8ac0af5 100644 --- a/migration-local.c +++ b/migration-local.c @@ -253,10 +253,65 @@ static size_t qemu_local_save_ram(QEMUFile *f, void *opaque, return RAM_SAVE_CONTROL_NOT_SUPP; } +static int qemu_local_ram_load(QEMUFile *f, void *opaque, + uint64_t flags) +{ + QEMUFileLocal *s = opaque; + ram_addr_t addr; + struct iovec iov; + ssize_t ret = -EINVAL; + + /* + * PIPE file descriptor will be received by another callback + * get_buffer. + */ + if (pipefd_passed) { + void *host; + /* + * Extract the page address from the 8-byte record and + * read the page data from the pipe. + */ + addr = qemu_get_be64(s->file); + host = qemu_get_ram_ptr(addr); + + iov.iov_base = host; + iov.iov_len = TARGET_PAGE_SIZE; + + /* The flag SPLICE_F_MOVE is introduced in kernel for the page + * flipping feature in QEMU, which will movie pages rather than + * copying, previously unused. + * + * If a move is not possible the kernel will transparently falls + * back to copying data. + * + * For older kernels the SPLICE_F_MOVE would be ignored and a copy + * would occur. + */ + ret = vmsplice(s->pipefd[0], &iov, 1, SPLICE_F_MOVE); + if (ret == -1) { + if (errno != EAGAIN && errno != EINTR) { + fprintf(stderr, "vmsplice() load error: %s", strerror(errno)); + return ret; + } + DPRINTF("vmsplice load error\n"); + } else if (ret == 0) { + DPRINTF(stderr, "load_page: zero read\n"); + } + + DPRINTF("vmsplice (read): %zu\n", ret); + return ret; + } + + return 0; +} + + + static const QEMUFileOps pipe_read_ops = { .get_fd = qemu_local_get_sockfd, .get_buffer = qemu_local_get_buffer, .close = qemu_local_close, + .hook_ram_load = qemu_local_ram_load }; static const QEMUFileOps pipe_write_ops = { -- 1.7.7.6