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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-4db6ec369fdsm1202614173.138.2024.10.07.09.06.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Oct 2024 09:06:24 -0700 (PDT) Date: Mon, 7 Oct 2024 12:06:21 -0400 From: Peter Xu To: Steve Sistare Cc: qemu-devel@nongnu.org, Fabiano Rosas , David Hildenbrand , Marcel Apfelbaum , Eduardo Habkost , Philippe Mathieu-Daude , Paolo Bonzini , "Daniel P. Berrange" , Markus Armbruster Subject: Re: [PATCH V2 07/13] migration: SCM_RIGHTS for QEMUFile Message-ID: References: <1727725244-105198-1-git-send-email-steven.sistare@oracle.com> <1727725244-105198-8-git-send-email-steven.sistare@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1727725244-105198-8-git-send-email-steven.sistare@oracle.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.153, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Sep 30, 2024 at 12:40:38PM -0700, Steve Sistare wrote: > Define functions to put/get file descriptors to/from a QEMUFile, for qio > channels that support SCM_RIGHTS. Maintain ordering such that > put(A), put(fd), put(B) > followed by > get(A), get(fd), get(B) > always succeeds. Other get orderings may succeed but are not guaranteed. > > Signed-off-by: Steve Sistare > --- > migration/qemu-file.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++--- > migration/qemu-file.h | 2 ++ > migration/trace-events | 2 ++ > 3 files changed, 83 insertions(+), 4 deletions(-) > > diff --git a/migration/qemu-file.c b/migration/qemu-file.c > index b6d2f58..7f951ab 100644 > --- a/migration/qemu-file.c > +++ b/migration/qemu-file.c > @@ -37,6 +37,11 @@ > #define IO_BUF_SIZE 32768 > #define MAX_IOV_SIZE MIN_CONST(IOV_MAX, 64) > > +typedef struct FdEntry { > + QTAILQ_ENTRY(FdEntry) entry; > + int fd; > +} FdEntry; > + > struct QEMUFile { > QIOChannel *ioc; > bool is_writable; > @@ -51,6 +56,9 @@ struct QEMUFile { > > int last_error; > Error *last_error_obj; > + > + bool fd_pass; > + QTAILQ_HEAD(, FdEntry) fds; > }; > > /* > @@ -109,6 +117,8 @@ static QEMUFile *qemu_file_new_impl(QIOChannel *ioc, bool is_writable) > object_ref(ioc); > f->ioc = ioc; > f->is_writable = is_writable; > + f->fd_pass = qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_FD_PASS); > + QTAILQ_INIT(&f->fds); > > return f; > } > @@ -310,6 +320,10 @@ static ssize_t coroutine_mixed_fn qemu_fill_buffer(QEMUFile *f) > int len; > int pending; > Error *local_error = NULL; > + g_autofree int *fds = NULL; > + size_t nfd = 0; > + int **pfds = f->fd_pass ? &fds : NULL; > + size_t *pnfd = f->fd_pass ? &nfd : NULL; > > assert(!qemu_file_is_writable(f)); > > @@ -325,10 +339,9 @@ static ssize_t coroutine_mixed_fn qemu_fill_buffer(QEMUFile *f) > } > > do { > - len = qio_channel_read(f->ioc, > - (char *)f->buf + pending, > - IO_BUF_SIZE - pending, > - &local_error); > + struct iovec iov = { f->buf + pending, IO_BUF_SIZE - pending }; > + len = qio_channel_readv_full(f->ioc, &iov, 1, pfds, pnfd, 0, > + &local_error); > if (len == QIO_CHANNEL_ERR_BLOCK) { > if (qemu_in_coroutine()) { > qio_channel_yield(f->ioc, G_IO_IN); > @@ -348,9 +361,65 @@ static ssize_t coroutine_mixed_fn qemu_fill_buffer(QEMUFile *f) > qemu_file_set_error_obj(f, len, local_error); > } > > + for (int i = 0; i < nfd; i++) { > + FdEntry *fde = g_new0(FdEntry, 1); > + fde->fd = fds[i]; > + QTAILQ_INSERT_TAIL(&f->fds, fde, entry); > + } > + > return len; > } > > +int qemu_file_put_fd(QEMUFile *f, int fd) > +{ > + int ret = 0; > + QIOChannel *ioc = qemu_file_get_ioc(f); > + Error *err = NULL; > + struct iovec iov = { (void *)" ", 1 }; > + > + /* > + * Send a dummy byte so qemu_fill_buffer on the receiving side does not > + * fail with a len=0 error. Flush first to maintain ordering wrt other > + * data. > + */ > + > + qemu_fflush(f); > + if (qio_channel_writev_full(ioc, &iov, 1, &fd, 1, 0, &err) < 1) { > + error_report_err(error_copy(err)); > + qemu_file_set_error_obj(f, -EIO, err); > + ret = -1; > + } > + trace_qemu_file_put_fd(f->ioc->name, fd, ret); > + return ret; > +} > + > +int qemu_file_get_fd(QEMUFile *f) > +{ > + int fd = -1; > + FdEntry *fde; > + > + if (!f->fd_pass) { > + Error *err = NULL; > + error_setg(&err, "%s does not support fd passing", f->ioc->name); > + error_report_err(error_copy(err)); > + qemu_file_set_error_obj(f, -EIO, err); > + goto out; > + } > + > + /* Force the dummy byte and its fd passenger to appear. */ > + qemu_peek_byte(f, 0); > + > + fde = QTAILQ_FIRST(&f->fds); > + if (fde) { > + qemu_get_byte(f); /* Drop the dummy byte */ Can we still try to get rid of this magical byte? Ideally this function should check for no byte but f->fds bening non-empty, if it is it could invoke qemu_fill_buffer(). OTOH, qemu_fill_buffer() needs to take len==0&&nfds!=0 as legal. Would that work? > + fd = fde->fd; > + QTAILQ_REMOVE(&f->fds, fde, entry); > + } > +out: > + trace_qemu_file_get_fd(f->ioc->name, fd); > + return fd; > +} > + > /** Closes the file > * > * Returns negative error value if any error happened on previous operations or > @@ -361,11 +430,17 @@ static ssize_t coroutine_mixed_fn qemu_fill_buffer(QEMUFile *f) > */ > int qemu_fclose(QEMUFile *f) > { > + FdEntry *fde, *next; > int ret = qemu_fflush(f); > int ret2 = qio_channel_close(f->ioc, NULL); > if (ret >= 0) { > ret = ret2; > } > + QTAILQ_FOREACH_SAFE(fde, &f->fds, entry, next) { > + warn_report("qemu_fclose: received fd %d was never claimed", fde->fd); > + close(fde->fd); > + g_free(fde); > + } > g_clear_pointer(&f->ioc, object_unref); > error_free(f->last_error_obj); > g_free(f); > diff --git a/migration/qemu-file.h b/migration/qemu-file.h > index 11c2120..3e47a20 100644 > --- a/migration/qemu-file.h > +++ b/migration/qemu-file.h > @@ -79,5 +79,7 @@ size_t qemu_get_buffer_at(QEMUFile *f, const uint8_t *buf, size_t buflen, > off_t pos); > > QIOChannel *qemu_file_get_ioc(QEMUFile *file); > +int qemu_file_put_fd(QEMUFile *f, int fd); > +int qemu_file_get_fd(QEMUFile *f); > > #endif > diff --git a/migration/trace-events b/migration/trace-events > index 5356fb5..345506b 100644 > --- a/migration/trace-events > +++ b/migration/trace-events > @@ -88,6 +88,8 @@ put_qlist_end(const char *field_name, const char *vmsd_name) "%s(%s)" > > # qemu-file.c > qemu_file_fclose(void) "" > +qemu_file_put_fd(const char *name, int fd, int ret) "ioc %s, fd %d -> status %d" > +qemu_file_get_fd(const char *name, int fd) "ioc %s -> fd %d" > > # ram.c > get_queued_page(const char *block_name, uint64_t tmp_offset, unsigned long page_abs) "%s/0x%" PRIx64 " page_abs=0x%lx" > -- > 1.8.3.1 > -- Peter Xu