When debugging a paravirtualized guest firmware, it results very
useful to dump the fw_cfg table.
Add a HMP command which displays the most useful fields.
We display each fw_cfg item data in hexadecimal (only the first 8
bytes):
$ (echo info fw_cfg; echo q) | qemu-system-x86_64 -S -monitor stdio
(qemu) info fw_cfg
Selector Well-Known Key Pathname ArchSpec Perm Size Order Hex Data
0x0000 signature RO 4 51454d55
0x0001 id RO 4 03000000
0x0002 uuid RO 16 0000000000000000..
0x0003 ram_size RO 8 0000000800000000
0x0004 nographic RO 2 0000
0x0005 nb_cpus RO 2 0100
0x000d numa RO 16 0000000000000000..
0x000e boot_menu RO 2 0000
0x000f max_cpus RO 2 0100
0x0019 file_dir RO 2052 0000000b00000000..
0x0021 file: etc/acpi/rsdp RO 20 160 5253442050545220..
0x0022 file: etc/acpi/tables RO 131072 130 4641435340000000..
0x0023 file: etc/boot-fail-wait RO 4 15 ffffffff
0x0024 file: etc/e820 RO 20 40 0000000000000000..
0x0025 file: etc/smbios/smbios-anchor RO 31 30 5f534d5f001f0208..
0x0026 file: etc/smbios/smbios-tables RO 321 20 011b000101020300..
0x0027 file: etc/system-states RO 6 90 800000818280
0x0028 file: etc/table-loader RO 4096 140 010000006574632f..
0x002a file: genroms/kvmvapic.bin RO 9216 55 55aa12060e0731c0..
0x0002 irq0_override * RO 4 01000000
0x0003 e820_tables * RO 324 0000000000000000..
0x0004 hpet * RO 121 0101a286800000d0..
(qemu) q
$ (echo info fw_cfg; echo q) | qemu-system-mips -S -monitor stdio
(qemu) info fw_cfg
This machine does not use fw_cfg
(qemu) q
$ (echo info fw_cfg; echo q) | qemu-system-ppc -S -monitor stdio
(qemu) info fw_cfg
Selector Well-Known Key Pathname ArchSpec Perm Size Order Hex Data
0x0000 signature RO 4 51454d55
0x0001 id RO 4 01000000
0x0002 uuid RO 16 0000000000000000..
0x0003 ram_size RO 8 0000000800000000
0x0004 nographic RO 2 0000
0x0005 nb_cpus RO 2 0100
0x0006 machine_id RO 2 0200
0x0007 kernel_addr RO 4 00000000
0x0008 kernel_size RO 4 00000000
0x0009 kernel_cmdline RO 4 00000000
0x000a initrd_addr RO 4 00000000
0x000b initdr_size RO 4 00000000
0x000c boot_device RO 2 6300
0x000e boot_menu RO 2 0000
0x000f max_cpus RO 2 0100
0x0019 file_dir RO 2052 0000000200000000..
0x0021 file: etc/boot-fail-wait RO 4 15 ffffffff
0x0000 width * RO 2 2003
0x0001 height * RO 2 5802
0x0002 depth * RO 2 2000
0x0003 tbfreq * RO 4 c04bfd00
0x0004 clockfreq * RO 4 80d6da0f
0x0005 is_kvm * RO 4 00000000
0x0009 busfreq * RO 4 8014ef03
(qemu) q
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
v2: Check fw_cfg != NULL (Michael)
Rename keys, display data in hexa (Laszlo)
---
hmp-commands-info.hx | 17 ++++++++++
hw/nvram/fw_cfg.c | 71 ++++++++++++++++++++++++++++++++++++++-
include/hw/nvram/fw_cfg.h | 2 ++
3 files changed, 89 insertions(+), 1 deletion(-)
diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
index cbee8b944d..2c9538c8da 100644
--- a/hmp-commands-info.hx
+++ b/hmp-commands-info.hx
@@ -916,6 +916,23 @@ STEXI
@item info sev
@findex info sev
Show SEV information.
+ETEXI
+
+ {
+ .name = "fw_cfg",
+ .args_type = "",
+ .params = "",
+ .help = "Display the table firmware configuration entries "
+ "registered by a paravirtualized machine. Helpful "
+ "when debugging guest firmwares.",
+ .cmd = hmp_info_fw_cfg,
+ },
+
+STEXI
+@item info fw_cfg
+@findex info fw_cfg
+Display the table firmware configuration entries registered by a paravirtualized
+machine. This information is useful when debugging guest firmwares.
ETEXI
STEXI
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 2a8d69ba07..4c82dcc125 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -35,6 +35,7 @@
#include "qemu/config-file.h"
#include "qemu/cutils.h"
#include "qapi/error.h"
+#include "monitor/monitor.h"
#include "qapi/qapi-commands-misc.h"
#define FW_CFG_FILE_SLOTS_DFLT 0x20
@@ -1273,7 +1274,18 @@ static FirmwareConfigurationItem *create_qmp_fw_cfg_item(FWCfgState *s,
return item;
}
-FirmwareConfigurationItemList *qmp_query_fw_cfg_items(Error **errp)
+/**
+ * query_fw_cfg_items:
+ *
+ * @use_hexdump: Whether to populate the @data field with the hexadecimal
+ * representation of the item data.
+ * @errp: Pointer to a NULL initialized error object.
+ *
+ * Returns: A list of @FirmwareConfigurationItem, reverse sorted by the
+ * item selector key.
+ */
+static FirmwareConfigurationItemList *query_fw_cfg_items(bool use_hexdump,
+ Error **errp)
{
FirmwareConfigurationItemList *item_list = NULL;
uint32_t max_entries;
@@ -1294,6 +1306,9 @@ FirmwareConfigurationItemList *qmp_query_fw_cfg_items(Error **errp)
if (!e->len) {
continue;
}
+ if (use_hexdump) {
+ qmp_hex_length = MIN(e->len, 8);
+ }
info = g_malloc0(sizeof(*info));
info->value = create_qmp_fw_cfg_item(s, e, arch, key,
@@ -1305,3 +1320,57 @@ FirmwareConfigurationItemList *qmp_query_fw_cfg_items(Error **errp)
return item_list;
}
+
+FirmwareConfigurationItemList *qmp_query_fw_cfg_items(Error **errp)
+{
+ return query_fw_cfg_items(false, errp);
+}
+
+void hmp_info_fw_cfg(Monitor *mon, const QDict *qdict)
+{
+ FirmwareConfigurationItemList *item_list, *method;
+ Error *err = NULL;
+
+ item_list = query_fw_cfg_items(true, &err);
+ if (!item_list) {
+ monitor_printf(mon, "This machine does not use fw_cfg\n");
+ return;
+ }
+ if (err) {
+ monitor_printf(mon, "Could not query fw_cfg entries: %s\n",
+ error_get_pretty(err));
+ error_free(err);
+ return;
+ }
+
+ monitor_printf(mon, "Selector Well-Known Key Pathname"
+ " ArchSpec Perm Size Order Hex Data\n");
+ for (method = item_list; method; method = method->next) {
+ if (method->value->has_path) {
+ monitor_printf(mon,
+ " 0x%04x file: %-28s %2s %7" PRId64
+ " %3" PRId64 " %-16s%s\n",
+ method->value->key,
+ method->value->path,
+ method->value->writeable ? "RW" : "RO",
+ method->value->size,
+ method->value->order,
+ method->value->data,
+ method->value->size > 8 ? ".." : "");
+ } else {
+ monitor_printf(mon,
+ " 0x%04x %-30s %c %2s %7" PRId64
+ " %-16s%s\n",
+ method->value->key,
+ method->value->has_keyname
+ ? method->value->keyname : "",
+ method->value->architecture_specific ? '*' : ' ',
+ method->value->writeable ? "RW" : "RO",
+ method->value->size,
+ method->value->data,
+ method->value->size > 8 ? ".." : "");
+ }
+ }
+
+ qapi_free_FirmwareConfigurationItemList(item_list);
+}
diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
index 83a0540b6c..5ac9adfe1f 100644
--- a/include/hw/nvram/fw_cfg.h
+++ b/include/hw/nvram/fw_cfg.h
@@ -243,4 +243,6 @@ bool fw_cfg_dma_enabled(void *opaque);
*/
const char *fw_cfg_arch_key_name(uint16_t key);
+void hmp_info_fw_cfg(Monitor *mon, const QDict *qdict);
+
#endif
--
2.20.1
* Philippe Mathieu-Daudé (philmd@redhat.com) wrote:
> When debugging a paravirtualized guest firmware, it results very
> useful to dump the fw_cfg table.
> Add a HMP command which displays the most useful fields.
> We display each fw_cfg item data in hexadecimal (only the first 8
> bytes):
>
> $ (echo info fw_cfg; echo q) | qemu-system-x86_64 -S -monitor stdio
> (qemu) info fw_cfg
> Selector Well-Known Key Pathname ArchSpec Perm Size Order Hex Data
> 0x0000 signature RO 4 51454d55
> 0x0001 id RO 4 03000000
> 0x0002 uuid RO 16 0000000000000000..
> 0x0003 ram_size RO 8 0000000800000000
> 0x0004 nographic RO 2 0000
> 0x0005 nb_cpus RO 2 0100
> 0x000d numa RO 16 0000000000000000..
> 0x000e boot_menu RO 2 0000
> 0x000f max_cpus RO 2 0100
> 0x0019 file_dir RO 2052 0000000b00000000..
> 0x0021 file: etc/acpi/rsdp RO 20 160 5253442050545220..
> 0x0022 file: etc/acpi/tables RO 131072 130 4641435340000000..
> 0x0023 file: etc/boot-fail-wait RO 4 15 ffffffff
> 0x0024 file: etc/e820 RO 20 40 0000000000000000..
> 0x0025 file: etc/smbios/smbios-anchor RO 31 30 5f534d5f001f0208..
> 0x0026 file: etc/smbios/smbios-tables RO 321 20 011b000101020300..
> 0x0027 file: etc/system-states RO 6 90 800000818280
> 0x0028 file: etc/table-loader RO 4096 140 010000006574632f..
> 0x002a file: genroms/kvmvapic.bin RO 9216 55 55aa12060e0731c0..
> 0x0002 irq0_override * RO 4 01000000
> 0x0003 e820_tables * RO 324 0000000000000000..
> 0x0004 hpet * RO 121 0101a286800000d0..
> (qemu) q
>
> $ (echo info fw_cfg; echo q) | qemu-system-mips -S -monitor stdio
> (qemu) info fw_cfg
> This machine does not use fw_cfg
> (qemu) q
>
> $ (echo info fw_cfg; echo q) | qemu-system-ppc -S -monitor stdio
> (qemu) info fw_cfg
> Selector Well-Known Key Pathname ArchSpec Perm Size Order Hex Data
> 0x0000 signature RO 4 51454d55
> 0x0001 id RO 4 01000000
> 0x0002 uuid RO 16 0000000000000000..
> 0x0003 ram_size RO 8 0000000800000000
> 0x0004 nographic RO 2 0000
> 0x0005 nb_cpus RO 2 0100
> 0x0006 machine_id RO 2 0200
> 0x0007 kernel_addr RO 4 00000000
> 0x0008 kernel_size RO 4 00000000
> 0x0009 kernel_cmdline RO 4 00000000
> 0x000a initrd_addr RO 4 00000000
> 0x000b initdr_size RO 4 00000000
> 0x000c boot_device RO 2 6300
> 0x000e boot_menu RO 2 0000
> 0x000f max_cpus RO 2 0100
> 0x0019 file_dir RO 2052 0000000200000000..
> 0x0021 file: etc/boot-fail-wait RO 4 15 ffffffff
> 0x0000 width * RO 2 2003
> 0x0001 height * RO 2 5802
> 0x0002 depth * RO 2 2000
> 0x0003 tbfreq * RO 4 c04bfd00
> 0x0004 clockfreq * RO 4 80d6da0f
> 0x0005 is_kvm * RO 4 00000000
> 0x0009 busfreq * RO 4 8014ef03
> (qemu) q
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
I think this is fine from an HMP view; one thought of something that
might be useful is an optional parameter to specify a particular key
that dumps the whole object; then if you're particularly desperate to
look at an acpi table you could do something like:
info fw_cfg "file: etc/acpi/tables"
and get a fun block of hex back.
But that's just a suggestion, so:
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> v2: Check fw_cfg != NULL (Michael)
> Rename keys, display data in hexa (Laszlo)
> ---
> hmp-commands-info.hx | 17 ++++++++++
> hw/nvram/fw_cfg.c | 71 ++++++++++++++++++++++++++++++++++++++-
> include/hw/nvram/fw_cfg.h | 2 ++
> 3 files changed, 89 insertions(+), 1 deletion(-)
>
> diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
> index cbee8b944d..2c9538c8da 100644
> --- a/hmp-commands-info.hx
> +++ b/hmp-commands-info.hx
> @@ -916,6 +916,23 @@ STEXI
> @item info sev
> @findex info sev
> Show SEV information.
> +ETEXI
> +
> + {
> + .name = "fw_cfg",
> + .args_type = "",
> + .params = "",
> + .help = "Display the table firmware configuration entries "
> + "registered by a paravirtualized machine. Helpful "
> + "when debugging guest firmwares.",
> + .cmd = hmp_info_fw_cfg,
> + },
> +
> +STEXI
> +@item info fw_cfg
> +@findex info fw_cfg
> +Display the table firmware configuration entries registered by a paravirtualized
> +machine. This information is useful when debugging guest firmwares.
> ETEXI
>
> STEXI
> diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
> index 2a8d69ba07..4c82dcc125 100644
> --- a/hw/nvram/fw_cfg.c
> +++ b/hw/nvram/fw_cfg.c
> @@ -35,6 +35,7 @@
> #include "qemu/config-file.h"
> #include "qemu/cutils.h"
> #include "qapi/error.h"
> +#include "monitor/monitor.h"
> #include "qapi/qapi-commands-misc.h"
>
> #define FW_CFG_FILE_SLOTS_DFLT 0x20
> @@ -1273,7 +1274,18 @@ static FirmwareConfigurationItem *create_qmp_fw_cfg_item(FWCfgState *s,
> return item;
> }
>
> -FirmwareConfigurationItemList *qmp_query_fw_cfg_items(Error **errp)
> +/**
> + * query_fw_cfg_items:
> + *
> + * @use_hexdump: Whether to populate the @data field with the hexadecimal
> + * representation of the item data.
> + * @errp: Pointer to a NULL initialized error object.
> + *
> + * Returns: A list of @FirmwareConfigurationItem, reverse sorted by the
> + * item selector key.
> + */
> +static FirmwareConfigurationItemList *query_fw_cfg_items(bool use_hexdump,
> + Error **errp)
> {
> FirmwareConfigurationItemList *item_list = NULL;
> uint32_t max_entries;
> @@ -1294,6 +1306,9 @@ FirmwareConfigurationItemList *qmp_query_fw_cfg_items(Error **errp)
> if (!e->len) {
> continue;
> }
> + if (use_hexdump) {
> + qmp_hex_length = MIN(e->len, 8);
> + }
>
> info = g_malloc0(sizeof(*info));
> info->value = create_qmp_fw_cfg_item(s, e, arch, key,
> @@ -1305,3 +1320,57 @@ FirmwareConfigurationItemList *qmp_query_fw_cfg_items(Error **errp)
>
> return item_list;
> }
> +
> +FirmwareConfigurationItemList *qmp_query_fw_cfg_items(Error **errp)
> +{
> + return query_fw_cfg_items(false, errp);
> +}
> +
> +void hmp_info_fw_cfg(Monitor *mon, const QDict *qdict)
> +{
> + FirmwareConfigurationItemList *item_list, *method;
> + Error *err = NULL;
> +
> + item_list = query_fw_cfg_items(true, &err);
> + if (!item_list) {
> + monitor_printf(mon, "This machine does not use fw_cfg\n");
> + return;
> + }
> + if (err) {
> + monitor_printf(mon, "Could not query fw_cfg entries: %s\n",
> + error_get_pretty(err));
> + error_free(err);
> + return;
> + }
> +
> + monitor_printf(mon, "Selector Well-Known Key Pathname"
> + " ArchSpec Perm Size Order Hex Data\n");
> + for (method = item_list; method; method = method->next) {
> + if (method->value->has_path) {
> + monitor_printf(mon,
> + " 0x%04x file: %-28s %2s %7" PRId64
> + " %3" PRId64 " %-16s%s\n",
> + method->value->key,
> + method->value->path,
> + method->value->writeable ? "RW" : "RO",
> + method->value->size,
> + method->value->order,
> + method->value->data,
> + method->value->size > 8 ? ".." : "");
> + } else {
> + monitor_printf(mon,
> + " 0x%04x %-30s %c %2s %7" PRId64
> + " %-16s%s\n",
> + method->value->key,
> + method->value->has_keyname
> + ? method->value->keyname : "",
> + method->value->architecture_specific ? '*' : ' ',
> + method->value->writeable ? "RW" : "RO",
> + method->value->size,
> + method->value->data,
> + method->value->size > 8 ? ".." : "");
> + }
> + }
> +
> + qapi_free_FirmwareConfigurationItemList(item_list);
> +}
> diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
> index 83a0540b6c..5ac9adfe1f 100644
> --- a/include/hw/nvram/fw_cfg.h
> +++ b/include/hw/nvram/fw_cfg.h
> @@ -243,4 +243,6 @@ bool fw_cfg_dma_enabled(void *opaque);
> */
> const char *fw_cfg_arch_key_name(uint16_t key);
>
> +void hmp_info_fw_cfg(Monitor *mon, const QDict *qdict);
> +
> #endif
> --
> 2.20.1
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
© 2016 - 2025 Red Hat, Inc.