meson.build: Make keyutils independent from keyring

Commit 0db0fbb ("Add conditional dependency for libkeyutils")
tried to provide a possibility for the user to disable keyutils
if not required by makeing it depend on the keyring feature. This
looked reasonable at a first glance (the unit test in tests/unit/
needs both), but the condition in meson.build fails if the feature
is meant to be detected automatically, and there is also another
spot in backends/meson.build where keyutils is used independently
from keyring. So let's remove the dependency on keyring again and
introduce a proper meson build option instead.

Cc: qemu-stable@nongnu.org
Fixes: 0db0fbb ("Add conditional dependency for libkeyutils")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1842
Message-ID: <20230824094208.255279-1-thuth@redhat.com>
Reviewed-by: "Daniel P. Berrangé" <berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

meson.build

@@ -1763,8 +1763,9 @@ if gnutls.found()
                      method: 'pkg-config')
 endif
 keyutils = not_found
-if get_option('keyring').enabled()
-  keyutils = dependency('libkeyutils', required: false, method: 'pkg-config')
+if not get_option('libkeyutils').auto() or have_block
+  keyutils = dependency('libkeyutils', required: get_option('libkeyutils'),
+                        method: 'pkg-config')
 endif
 
 has_gettid = cc.has_function('gettid')
@@ -4229,6 +4230,7 @@ endif
 summary_info += {'AF_ALG support':    have_afalg}
 summary_info += {'rng-none':          get_option('rng_none')}
 summary_info += {'Linux keyring':     have_keyring}
+summary_info += {'Linux keyutils':    keyutils}
 summary(summary_info, bool_yn: true, section: 'Crypto')
 
 # UI

meson_options.txt

@@ -121,6 +121,8 @@ option('avx512bw', type: 'feature', value: 'auto',
        description: 'AVX512BW optimizations')
 option('keyring', type: 'feature', value: 'auto',
        description: 'Linux keyring support')
+option('libkeyutils', type: 'feature', value: 'auto',
+       description: 'Linux keyutils support')
 
 option('af_xdp', type : 'feature', value : 'auto',
        description: 'AF_XDP network backend support')

scripts/meson-buildoptions.sh

@@ -122,6 +122,7 @@ meson_options_help() {
   printf "%s\n" '  libdaxctl       libdaxctl support'
   printf "%s\n" '  libdw           debuginfo support'
   printf "%s\n" '  libiscsi        libiscsi userspace initiator'
+  printf "%s\n" '  libkeyutils     Linux keyutils support'
   printf "%s\n" '  libnfs          libnfs block device driver'
   printf "%s\n" '  libpmem         libpmem support'
   printf "%s\n" '  libssh          ssh block device support'
@@ -345,6 +346,8 @@ _meson_option_parse() {
     --libexecdir=*) quote_sh "-Dlibexecdir=$2" ;;
     --enable-libiscsi) printf "%s" -Dlibiscsi=enabled ;;
     --disable-libiscsi) printf "%s" -Dlibiscsi=disabled ;;
+    --enable-libkeyutils) printf "%s" -Dlibkeyutils=enabled ;;
+    --disable-libkeyutils) printf "%s" -Dlibkeyutils=disabled ;;
     --enable-libnfs) printf "%s" -Dlibnfs=enabled ;;
     --disable-libnfs) printf "%s" -Dlibnfs=disabled ;;
     --enable-libpmem) printf "%s" -Dlibpmem=enabled ;;