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Tue, 19 May 2020 22:34:07 +0000 (UTC) Subject: Re: [PATCH v6 2/5] softmmu/vl: Let -fw_cfg option take a 'blob_id' argument To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , qemu-devel@nongnu.org References: <20200519182024.14638-1-philmd@redhat.com> <20200519182024.14638-3-philmd@redhat.com> From: Laszlo Ersek Message-ID: Date: Wed, 20 May 2020 00:34:06 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200519182024.14638-3-philmd@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=lersek@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/18 23:56:10 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , "=?UTF-8?Q?Daniel_P._Berrang=c3=a9?=" , Eduardo Habkost , Gerd Hoffmann Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 05/19/20 20:20, Philippe Mathieu-Daudé wrote: > The 'blob_id' argument refers to a QOM object able to produce > data consumable by the fw_cfg device. The producer object must > implement the FW_CFG_DATA_GENERATOR interface. OK, this answers my OBJECT_CHECK() question under patch #1 (in the negative -- an assert would be wrong). > > Signed-off-by: Philippe Mathieu-Daudé > --- > softmmu/vl.c | 17 +++++++++++++---- > 1 file changed, 13 insertions(+), 4 deletions(-) > > diff --git a/softmmu/vl.c b/softmmu/vl.c > index ae5451bc23..f76c53ad2e 100644 > --- a/softmmu/vl.c > +++ b/softmmu/vl.c > @@ -489,6 +489,10 @@ static QemuOptsList qemu_fw_cfg_opts = { > .name = "string", > .type = QEMU_OPT_STRING, > .help = "Sets content of the blob to be inserted from a string", > + }, { > + .name = "blob_id", > + .type = QEMU_OPT_STRING, > + .help = "Sets id of the object generating fw_cfg blob to be used", > }, > { /* end of list */ } > }, > @@ -2020,7 +2024,7 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp) > { > gchar *buf; > size_t size; > - const char *name, *file, *str; > + const char *name, *file, *str, *blob_id; > FWCfgState *fw_cfg = (FWCfgState *) opaque; > > if (fw_cfg == NULL) { > @@ -2030,14 +2034,17 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp) > name = qemu_opt_get(opts, "name"); > file = qemu_opt_get(opts, "file"); > str = qemu_opt_get(opts, "string"); > + blob_id = qemu_opt_get(opts, "blob_id"); > > /* we need name and either a file or the content string */ (1) Please update this comment. If the option is given, we need the name, and exactly one of: file, content string, blob_id. > - if (!(nonempty_str(name) && (nonempty_str(file) || nonempty_str(str)))) { > + if (!(nonempty_str(name) > + && (nonempty_str(file) || nonempty_str(str) || nonempty_str(blob_id))) > + ) { > error_setg(errp, "invalid argument(s)"); > return -1; > } (2) Coding style: does QEMU keep operators on the left or on the right when breaking subconditions to new lines? (I vaguely recall "to the right", but I could be wrong... Well, "hw/nvram/fw_cfg.c" has at least 7 examples of the operator being on the right.) > - if (nonempty_str(file) && nonempty_str(str)) { > - error_setg(errp, "file and string are mutually exclusive"); > + if (nonempty_str(file) && nonempty_str(str) && nonempty_str(blob_id)) { > + error_setg(errp, "file, string and blob_id are mutually exclusive"); > return -1; > } (3) I believe this catches only when all three of name/string/blob_id are given. But we should continue catching "two given". How about reworking both "if"s, *and* the comment at (1) at the same time, into: if (!nonempty_str(name) || nonempty_str(file) + nonempty_str(str) + nonempty_str(blob_id) != 1) { error_setg(errp, "name, plus exactly one of file, string and blob_id, " "are needed"); return -1; } (Regarding the addition, nonempty_str() returns a "bool", which is a macro to _Bool, which is promoted to "int" or "unsigned int".) > if (strlen(name) > FW_CFG_MAX_FILE_PATH - 1) { > @@ -2052,6 +2059,8 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp) > if (nonempty_str(str)) { > size = strlen(str); /* NUL terminator NOT included in fw_cfg blob */ > buf = g_memdup(str, size); > + } else if (nonempty_str(blob_id)) { > + return fw_cfg_add_from_generator(fw_cfg, name, blob_id, errp); > } else { > GError *err = NULL; > if (!g_file_get_contents(file, &buf, &size, &err)) { > (4) The "-fw_cfg" command line option is documented in both the qemu(1) manual, and the "docs/specs/fw_cfg.txt" file. I think we may have to update those. In particular I mean *where* the option is documented (in both texts). In the manual, "-fw_cfg" is currently under "Debug/Expert options", but that will no longer apply (I think?) after this series. Similarly, in "docs/specs/fw_cfg.txt", the section is called "Externally Provided Items" -- but that might not be strictly true any more either. Maybe leave the current "-fw_cfg" mentions in peace, and document "-fw_cfg blob_id=..." separately (in different docs sections)? The "fw_cfg generators" concept could deserve dedicated sections. Sorry that I can't make a good concrete suggestion. :( Thanks, Laszlo