diff --git a/packages/conf-lld/conf-lld.1/opam b/packages/conf-lld/conf-lld.1/opam
new file mode 100644
index 00000000000..d511798c132
--- /dev/null
+++ b/packages/conf-lld/conf-lld.1/opam
@@ -0,0 +1,29 @@
+opam-version: "2.0"
+maintainer: "Léo Andrès <contact@ndrs.fr>"
+authors: "The LLVM team"
+homepage: "http://llvm.org"
+bug-reports: "https://llvm.org/bugs/"
+license: "MIT"
+build: [
+  ["wasm-ld" "-version"] { os-distribution != "homebrew" }
+]
+depends: [
+]
+depexts: [
+  ["lld"] { os-family = "alpine" }
+  ["lld"] { os-family = "arch" }
+  ["lld"] { os-family = "debian" }
+  ["lld"] { os-family = "opensuse" }
+  ["lld"] { os-family = "suse" }
+  ["lld"] { os-family = "ubuntu" }
+
+  ["lld"] { os-distribution = "centos" }
+  ["lld"] { os-distribution = "fedora" }
+  ["llvm"] { os-distribution = "homebrew" }
+]
+x-ci-accept-failures: [
+  "ubuntu-20.04" # does not have wasm-ld
+]
+available: os-distribution != "freebsd"
+synopsis: "Virtual package relying on lld installation"
+flags: conf
diff --git a/packages/conf-rust-llvm/conf-rust-llvm.1/opam b/packages/conf-rust-llvm/conf-rust-llvm.1/opam
new file mode 100644
index 00000000000..f9700796fd0
--- /dev/null
+++ b/packages/conf-rust-llvm/conf-rust-llvm.1/opam
@@ -0,0 +1,27 @@
+opam-version: "2.0"
+maintainer: "Léo Andrès <contact@ndrs.fr>"
+authors: "Léo Andrès <contact@ndrs.fr>"
+homepage: "https://github.com/ocaml/opam-repository"
+bug-reports: "https://github.com/ocaml/opam-repository/issues"
+license: "MIT"
+build: [
+  ["which" "rust-lld"] { os-distribution != "homebrew" }
+]
+depends: [
+  "conf-which" {build}
+  "conf-rust"
+  "conf-llvm"
+  "conf-lld"
+]
+depexts: [
+  ["rust-llvm"] { os-family = "alpine" }
+  ["rust-llvm"] { os-family = "arch" }
+  ["rust-llvm"] { os-family = "debian" }
+  ["rust-llvm"] { os-family = "ubuntu" }
+  ["rust-llvm"] { os-family = "opensuse" }
+  ["rust-llvm"] { os-family = "suse" }
+  ["rust-llvm"] { os-distribution = "centos" }
+]
+available: os-distribution != "freebsd" & os-distribution != "fedora"
+synopsis: "Virtual package relying on an installation of the integration of Rust with LLVM tools"
+flags: conf
diff --git a/packages/conf-rust-wasm/conf-rust-wasm.1/opam b/packages/conf-rust-wasm/conf-rust-wasm.1/opam
new file mode 100644
index 00000000000..8578fb2c0c4
--- /dev/null
+++ b/packages/conf-rust-wasm/conf-rust-wasm.1/opam
@@ -0,0 +1,24 @@
+opam-version: "2.0"
+maintainer: "Léo Andrès <contact@ndrs.fr>"
+authors: "Léo Andrès <contact@ndrs.fr>"
+homepage: "https://github.com/ocaml/opam-repository"
+bug-reports: "https://github.com/ocaml/opam-repository/issues"
+license: "MIT"
+build: [
+  ["sh" "-c" "rustc --print target-list | grep -q 'wasm32-unknown-unknown'" ]
+]
+depends: [
+  "conf-rust" {build}
+]
+depexts: [
+  ["rust-wasm"] { os-family = "alpine" }
+  ["rust-wasm"] { os-family = "arch" }
+  ["libstd-rust-dev-wasm32"] { os-family = "debian" }
+  ["libstd-rust-dev-wasm32"] { os-family = "ubuntu" }
+
+  ["libstd-rust-dev-wasm32"] { os-distribution = "centos" }
+  ["rust-std-static-wasm32-unknown-unknown"] { os-distribution = "fedora" }
+]
+available: os-family != "opensuse" & os-family != "suse" & os-distribution != "homebrew"
+synopsis: "Virtual package relying on an installation of standard Rust libraries including development files, needed to cross-compile Rust programs to the wasm32-unknown-unknown and wasm32-wasip1/wasm32-wasip2 targets"
+flags: conf