sd-boot: allow setting the log level through SMBIOS 11

Allow configuring the log level used by sd-boot by setting
`io.systemd.boot.loglevel=<level>` as SMBIOS type 11 string.
`info` is used if unset.

man/smbios-type-11.xml

@@ -80,10 +80,20 @@
 
         <listitem><para>This allows inserting additional entries into the <command>systemd-boot</command>
         menu. For details see
-        <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry></para>
+        <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 
         <xi:include href="version-info.xml" xpointer="v258"/></listitem>
       </varlistentry>
+
+      <varlistentry>
+        <term><varname>io.systemd.boot.loglevel=</varname><replaceable>LEVEL</replaceable></term>
+
+        <listitem><para>This allows configuration of the log level, and is read by <command>systemd-boot</command>.
+        For details see
+        <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
+
+        <xi:include href="version-info.xml" xpointer="v259"/></listitem>
+      </varlistentry>
     </variablelist>
   </refsect1>
 

man/systemd-boot.xml

@@ -640,6 +640,16 @@ uki-url http://example.com/somedir/fooos.efi</programlisting>
 
         <xi:include href="version-info.xml" xpointer="v258"/></listitem>
       </varlistentry>
+
+      <varlistentry>
+        <term><varname>io.systemd.boot.loglevel</varname></term>
+        <listitem><para>If set, the value of this string is used as log level. Valid values (from most to
+        least critical) are <literal>emerg</literal>, <literal>alert</literal>, <literal>crit</literal>,
+        <literal>err</literal>, <literal>warning</literal>, <literal>notice</literal>, <literal>info</literal>,
+        and <literal>debug</literal>.</para>
+
+        <xi:include href="version-info.xml" xpointer="v259"/></listitem>
+      </varlistentry>
     </variablelist>
   </refsect1>
 

src/boot/boot.c

@@ -2991,6 +2991,9 @@ static EFI_STATUS run(EFI_HANDLE image) {
         uint64_t init_usec;
         bool menu = false;
 
+        /* set loglevel early to simplify debugging before loader.conf is loaded */
+        log_set_max_level_from_smbios();
+
         init_usec = time_usec();
 
         err = BS->HandleProtocol(image, MAKE_GUID_PTR(EFI_LOADED_IMAGE_PROTOCOL), (void **) &loaded_image);

src/boot/efi-log.c

@@ -3,7 +3,9 @@
 #include "efi-log.h"
 #include "efi-string-table.h"
 #include "proto/rng.h"
+#include "smbios.h"
 #include "util.h"
+#include "vmm.h"
 
 static unsigned log_count = 0;
 static LogLevel log_max_level = LOG_INFO;
@@ -57,6 +59,21 @@ int log_set_max_level_from_string(const char *e) {
         return 0;
 }
 
+void log_set_max_level_from_smbios(void) {
+        int r;
+
+        if (is_confidential_vm())
+                return; /* Don't consume SMBIOS in Confidential Computing contexts */
+
+        const char *level_str = smbios_find_oem_string("io.systemd.boot.loglevel=", /* after= */ NULL);
+        if (!level_str)
+                return;
+
+        r = log_set_max_level_from_string(level_str);
+        if (r < 0)
+                log_warning("Failed to parse log level '%s', ignoring.", level_str);
+}
+
 void freeze(void) {
         for (;;)
                 BS->Stall(60 * 1000 * 1000);

src/boot/efi-log.h

@@ -40,6 +40,7 @@ const char* log_level_to_string(LogLevel l) _const_;
 LogLevel log_get_max_level(void) _pure_;
 int log_set_max_level(LogLevel level);
 int log_set_max_level_from_string(const char *e);
+void log_set_max_level_from_smbios(void);
 
 _noreturn_ void freeze(void);
 void log_wait(void);