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[201.43.216.47]) by smtp.gmail.com with ESMTPSA id k27-20020a9f30db000000b00387499c5353sm5472697uab.39.2022.08.15.12.20.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 15 Aug 2022 12:20:25 -0700 (PDT) Message-ID: <60d6f521-fec2-e561-fc15-825aeeda9d44@gmail.com> Date: Mon, 15 Aug 2022 16:20:22 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH for-7.2 v2 14/20] qmp/hmp, device_tree.c: introduce dumpdtb Content-Language: en-US To: "Dr. David Alan Gilbert" Cc: David Gibson , qemu-devel@nongnu.org, alistair.francis@wdc.com References: <20220805093948.82561-1-danielhb413@gmail.com> <20220805093948.82561-15-danielhb413@gmail.com> <7a5a55f5-2e60-e34b-f84a-85ae4c122f7f@gmail.com> From: Daniel Henrique Barboza In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::e29; envelope-from=danielhb413@gmail.com; helo=mail-vs1-xe29.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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" On 8/15/22 15:31, Dr. David Alan Gilbert wrote: > * Daniel Henrique Barboza (danielhb413@gmail.com) wrote: >> >> >> On 8/8/22 00:30, David Gibson wrote: >>> On Fri, Aug 05, 2022 at 06:39:42AM -0300, Daniel Henrique Barboza wrote: >>>> To save the FDT blob we have the '-machine dumpdtb=' property. >>>> With this property set, the machine saves the FDT in and exit. >>>> The created file can then be converted to plain text dts format using >>>> 'dtc'. >>>> >>>> There's nothing particularly sophisticated into saving the FDT that >>>> can't be done with the machine at any state, as long as the machine has >>>> a valid FDT to be saved. >>>> >>>> The 'dumpdtb' command receives a 'filename' paramenter and, if a valid >>>> FDT is available, it'll save it in a file 'filename'. In short, this is >>>> a '-machine dumpdtb' that can be fired on demand via QMP/HMP. >>>> >>>> A valid FDT consists of a FDT that was created using libfdt being >>>> retrieved via 'current_machine->fdt' in device_tree.c. This condition is >>>> met by most FDT users in QEMU. >>> >>> On spapr at least, the fdt can change at runtime (due to hotplugs). >>> So we need to think about concurrency between fdt updates and dumping >>> it with this command. I'm assuming it's protected by the BQL, but I'm >>> wondering if we should outright state that somewhere for clarity. >> >> Your assumption is right. It is protected by BQL since it's always executed >> in-band. To not hold BQL we would need to declare an extra flag "allow-oob" >> to execute the command out-of-band. >> >> I'll mention in the commit msg that we're holding BQL. I'll do the same for >> the 'info fdt' commit msg. > > Is the update of the FDT also protected that way? Yes. At least for the pseries machine, the only machine we have ATM that updates the FDT after boot, without hotplug/unplug, and uses libfdt. The update of the pseries FDT occurs in the h_client_architecture_support hcall, which is always called holding BQL (either via kvm_arch_handle_exit() or emulate_spapr_hypercall). > (I guess hotplug commands are also protected by the bql - but is the > hotplug completion?) Hotplug completion is protected by BQL in all machines, as far as I know. Thanks, Daniel > > Dave >> >> Thanks, >> >> >> Daniel >> >> >>> >>>> >>>> Cc: Dr. David Alan Gilbert >>>> Signed-off-by: Daniel Henrique Barboza >>>> --- >>>> hmp-commands.hx | 13 +++++++++++++ >>>> include/monitor/hmp.h | 1 + >>>> include/sysemu/device_tree.h | 1 + >>>> monitor/hmp-cmds.c | 12 ++++++++++++ >>>> monitor/qmp-cmds.c | 13 +++++++++++++ >>>> qapi/machine.json | 17 +++++++++++++++++ >>>> softmmu/device_tree.c | 18 ++++++++++++++++++ >>>> 7 files changed, 75 insertions(+) >>>> >>>> diff --git a/hmp-commands.hx b/hmp-commands.hx >>>> index 182e639d14..d2554e9701 100644 >>>> --- a/hmp-commands.hx >>>> +++ b/hmp-commands.hx >>>> @@ -1800,3 +1800,16 @@ ERST >>>> "\n\t\t\t\t\t limit on a specified virtual cpu", >>>> .cmd = hmp_cancel_vcpu_dirty_limit, >>>> }, >>>> + >>>> +SRST >>>> +``dumpdtb`` *filename* >>>> + Save the FDT in the 'filename' file to be decoded using dtc. >>>> + Requires 'libfdt' support. >>>> +ERST >>>> + { >>>> + .name = "dumpdtb", >>>> + .args_type = "filename:s", >>>> + .params = "[filename] file to save the FDT", >>>> + .help = "save the FDT in the 'filename' file to be decoded using dtc", >>>> + .cmd = hmp_dumpdtb, >>>> + }, >>>> diff --git a/include/monitor/hmp.h b/include/monitor/hmp.h >>>> index a618eb1e4e..d7f324da59 100644 >>>> --- a/include/monitor/hmp.h >>>> +++ b/include/monitor/hmp.h >>>> @@ -134,6 +134,7 @@ void hmp_calc_dirty_rate(Monitor *mon, const QDict *qdict); >>>> void hmp_set_vcpu_dirty_limit(Monitor *mon, const QDict *qdict); >>>> void hmp_cancel_vcpu_dirty_limit(Monitor *mon, const QDict *qdict); >>>> void hmp_info_vcpu_dirty_limit(Monitor *mon, const QDict *qdict); >>>> +void hmp_dumpdtb(Monitor *mon, const QDict *qdict); >>>> void hmp_human_readable_text_helper(Monitor *mon, >>>> HumanReadableText *(*qmp_handler)(Error **)); >>>> void hmp_info_stats(Monitor *mon, const QDict *qdict); >>>> diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h >>>> index ef060a9759..bf7684e4ed 100644 >>>> --- a/include/sysemu/device_tree.h >>>> +++ b/include/sysemu/device_tree.h >>>> @@ -136,6 +136,7 @@ int qemu_fdt_add_path(void *fdt, const char *path); >>>> } while (0) >>>> void qemu_fdt_dumpdtb(void *fdt, int size); >>>> +void qemu_fdt_qmp_dumpdtb(const char *filename, Error **errp); >>>> /** >>>> * qemu_fdt_setprop_sized_cells_from_array: >>>> diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c >>>> index c6cd6f91dd..d23ec85f9d 100644 >>>> --- a/monitor/hmp-cmds.c >>>> +++ b/monitor/hmp-cmds.c >>>> @@ -2472,3 +2472,15 @@ exit: >>>> exit_no_print: >>>> error_free(err); >>>> } >>>> + >>>> +void hmp_dumpdtb(Monitor *mon, const QDict *qdict) >>>> +{ >>>> + const char *filename = qdict_get_str(qdict, "filename"); >>>> + Error *local_err = NULL; >>>> + >>>> + qmp_dumpdtb(filename, &local_err); >>>> + >>>> + if (local_err) { >>>> + error_report_err(local_err); >>>> + } >>>> +} >>>> diff --git a/monitor/qmp-cmds.c b/monitor/qmp-cmds.c >>>> index 7314cd813d..8415aca08c 100644 >>>> --- a/monitor/qmp-cmds.c >>>> +++ b/monitor/qmp-cmds.c >>>> @@ -45,6 +45,7 @@ >>>> #include "hw/intc/intc.h" >>>> #include "hw/rdma/rdma.h" >>>> #include "monitor/stats.h" >>>> +#include "sysemu/device_tree.h" >>>> NameInfo *qmp_query_name(Error **errp) >>>> { >>>> @@ -596,3 +597,15 @@ bool apply_str_list_filter(const char *string, strList *list) >>>> } >>>> return false; >>>> } >>>> + >>>> +#ifdef CONFIG_FDT >>>> +void qmp_dumpdtb(const char *filename, Error **errp) >>>> +{ >>>> + return qemu_fdt_qmp_dumpdtb(filename, errp); >>>> +} >>>> +#else >>>> +void qmp_dumpdtb(const char *filename, Error **errp) >>>> +{ >>>> + error_setg(errp, "dumpdtb requires libfdt"); >>>> +} >>>> +#endif >>>> diff --git a/qapi/machine.json b/qapi/machine.json >>>> index 6afd1936b0..aeb013f3dd 100644 >>>> --- a/qapi/machine.json >>>> +++ b/qapi/machine.json >>>> @@ -1664,3 +1664,20 @@ >>>> '*size': 'size', >>>> '*max-size': 'size', >>>> '*slots': 'uint64' } } >>>> + >>>> +## >>>> +# @dumpdtb: >>>> +# >>>> +# Save the FDT in dtb format. Requires 'libfdt' support. >>>> +# >>>> +# @filename: name of the FDT file to be created >>>> +# >>>> +# Since: 7.2 >>>> +# >>>> +# Example: >>>> +# {"execute": "dumpdtb"} >>>> +# "arguments": { "filename": "/tmp/fdt.dtb" } } >>>> +# >>>> +## >>>> +{ 'command': 'dumpdtb', >>>> + 'data': { 'filename': 'str' } } >>>> diff --git a/softmmu/device_tree.c b/softmmu/device_tree.c >>>> index 6ca3fad285..cd487ddd4d 100644 >>>> --- a/softmmu/device_tree.c >>>> +++ b/softmmu/device_tree.c >>>> @@ -643,3 +643,21 @@ out: >>>> g_free(propcells); >>>> return ret; >>>> } >>>> + >>>> +void qemu_fdt_qmp_dumpdtb(const char *filename, Error **errp) >>>> +{ >>>> + int size; >>>> + >>>> + if (!current_machine->fdt) { >>>> + error_setg(errp, "Unable to find the machine FDT"); >>>> + return; >>>> + } >>>> + >>>> + size = fdt_totalsize(current_machine->fdt); >>>> + >>>> + if (g_file_set_contents(filename, current_machine->fdt, size, NULL)) { >>>> + return; >>>> + } >>>> + >>>> + error_setg(errp, "Error when saving machine FDT to file %s", filename); >>>> +} >>> >>