Preserve return registers for unhandled Penguin hypercalls

build.sh

@@ -122,10 +122,37 @@ build_system_target_list() {
 
 build_system_lib_list() {
     local arch
+    local target
+    local lib
+    local libs=()
 
     IFS=',' read -ra split_arches <<< "$PENGUIN_SYSTEM_ARCHES"
     for arch in "${split_arches[@]}"; do
-        printf "libqemu-system-%s.so\n" "$arch"
+        target="$(penguin_system_arch_to_qemu_target "$arch")"
+        lib="libqemu-system-${target%-softmmu}.so"
+        if append_unique "$lib" "${libs[@]}"; then
+            libs+=("$lib")
+        fi
+    done
+
+    printf "%s\n" "${libs[@]}"
+}
+
+stage_system_lib_aliases() {
+    local arch
+    local target
+    local source
+    local alias
+
+    IFS=',' read -ra split_arches <<< "$PENGUIN_SYSTEM_ARCHES"
+    for arch in "${split_arches[@]}"; do
+        target="$(penguin_system_arch_to_qemu_target "$arch")"
+        source="build-system/libqemu-system-${target%-softmmu}.so"
+        alias="build-system/libqemu-system-${arch}.so"
+
+        if [ "$source" != "$alias" ]; then
+            cp -f "$source" "$alias"
+        fi
     done
 }
 
@@ -148,6 +175,7 @@ configure_build_dir build-system \
 
 mapfile -t system_libs < <(build_system_lib_list)
 ninja -C build-system "${system_libs[@]}" qemu-img
+stage_system_lib_aliases
 python3 scripts/penguin-cffi-gen.py \
     --mode system \
     --build-dir build-system \

include/system/penguin.h

@@ -28,6 +28,10 @@ typedef void (*penguin_mmio_write_cb_t)(uint64_t addr, uint64_t data,
 
 void set_penguin_guest_hypercall_callback(penguin_guest_hypercall_cb_t cb,
                                           void *opaque);
+void penguin_register_guest_hypercall(uint64_t nr);
+void penguin_unregister_guest_hypercall(uint64_t nr);
+void penguin_clear_guest_hypercalls(void);
+bool penguin_guest_hypercall_registered(uint64_t nr);
 void set_kvm_penguin_hypercall_callback(kvm_penguin_hypercall_cb_t cb);
 
 bool penguin_handle_guest_hypercall(CPUState *cs, uint64_t nr,

scripts/penguin-cffi-gen.py

@@ -100,6 +100,10 @@
 
 void set_penguin_guest_hypercall_callback(penguin_guest_hypercall_cb_t cb,
                                           void *opaque);
+void penguin_register_guest_hypercall(uint64_t nr);
+void penguin_unregister_guest_hypercall(uint64_t nr);
+void penguin_clear_guest_hypercalls(void);
+bool penguin_guest_hypercall_registered(uint64_t nr);
 void set_kvm_penguin_hypercall_callback(kvm_penguin_hypercall_cb_t cb);
 void set_kvm_penguin_after_guest_init_callback(
     kvm_penguin_after_guest_init_cb_t cb, void *opaque);

system/penguin.c

@@ -15,6 +15,54 @@ typedef struct PenguinMmioRegion {
 static penguin_guest_hypercall_cb_t penguin_guest_hypercall_cb;
 static void *penguin_guest_hypercall_opaque;
 static kvm_penguin_hypercall_cb_t kvm_penguin_hypercall_cb;
+static GHashTable *penguin_guest_hypercall_numbers;
+
+static void penguin_guest_hypercalls_init(void)
+{
+    if (!penguin_guest_hypercall_numbers) {
+        penguin_guest_hypercall_numbers = g_hash_table_new_full(g_int64_hash,
+                                                                g_int64_equal,
+                                                                g_free, NULL);
+    }
+}
+
+void __attribute__((visibility("default")))
+penguin_register_guest_hypercall(uint64_t nr)
+{
+    uint64_t *key;
+
+    penguin_guest_hypercalls_init();
+    if (g_hash_table_contains(penguin_guest_hypercall_numbers, &nr)) {
+        return;
+    }
+
+    key = g_new(uint64_t, 1);
+    *key = nr;
+    g_hash_table_add(penguin_guest_hypercall_numbers, key);
+}
+
+void __attribute__((visibility("default")))
+penguin_unregister_guest_hypercall(uint64_t nr)
+{
+    if (penguin_guest_hypercall_numbers) {
+        g_hash_table_remove(penguin_guest_hypercall_numbers, &nr);
+    }
+}
+
+void __attribute__((visibility("default")))
+penguin_clear_guest_hypercalls(void)
+{
+    if (penguin_guest_hypercall_numbers) {
+        g_hash_table_remove_all(penguin_guest_hypercall_numbers);
+    }
+}
+
+bool __attribute__((visibility("default")))
+penguin_guest_hypercall_registered(uint64_t nr)
+{
+    return penguin_guest_hypercall_numbers &&
+           g_hash_table_contains(penguin_guest_hypercall_numbers, &nr);
+}
 
 void __attribute__((visibility("default")))
 set_penguin_guest_hypercall_callback(penguin_guest_hypercall_cb_t cb,
@@ -36,7 +84,8 @@ bool penguin_handle_guest_hypercall(CPUState *cs, uint64_t nr,
                                     uint64_t a4, uint64_t a5,
                                     uint64_t *ret)
 {
-    if (penguin_guest_hypercall_cb) {
+    if (penguin_guest_hypercall_cb &&
+        penguin_guest_hypercall_registered(nr)) {
         return penguin_guest_hypercall_cb(cs, nr, a0, a1, a2, a3, a4, a5,
                                           ret,
                                           penguin_guest_hypercall_opaque) == 0;

target/arm/tcg/op_helper.c

@@ -95,7 +95,7 @@ uint64_t HELPER(penguin_guest_hypercall)(CPUARMState *env, uint64_t nr,
     if (penguin_handle_guest_hypercall(cs, nr, a0, a1, a2, a3, a4, 0, &ret)) {
         return ret;
     }
-    return 0;
+    return a0;
 }
 
 uint64_t HELPER(neon_tbl)(CPUARMState *env, uint32_t desc,

target/loongarch/tcg/op_helper.c

@@ -35,7 +35,7 @@ target_ulong helper_penguin_guest_hypercall(CPULoongArchState *env,
     if (penguin_handle_guest_hypercall(cs, nr, a0, a1, a2, a3, a4, 0, &ret)) {
         return ret;
     }
-    return 0;
+    return a0;
 }
 
 target_ulong helper_bitrev_w(target_ulong rj)

target/mips/tcg/op_helper.c

@@ -62,7 +62,7 @@ target_ulong helper_penguin_guest_hypercall(CPUMIPSState *env, target_ulong nr,
     if (penguin_handle_guest_hypercall(cs, nr, a0, a1, a2, a3, a4, 0, &ret)) {
         return ret;
     }
-    return 0;
+    return nr;
 }
 
 target_ulong helper_rotx(target_ulong rs, uint32_t shift, uint32_t shiftx,

target/ppc/misc_helper.c

@@ -55,7 +55,7 @@ target_ulong helper_penguin_guest_hypercall(CPUPPCState *env, target_ulong nr,
     if (penguin_handle_guest_hypercall(cs, nr, a0, a1, a2, a3, a4, 0, &ret)) {
         return ret;
     }
-    return 0;
+    return a0;
 }
 
 void helper_spr_core_write_generic(CPUPPCState *env, uint32_t sprn,

target/riscv/op_helper.c

@@ -60,7 +60,7 @@ target_ulong helper_penguin_guest_hypercall(CPURISCVState *env, target_ulong nr,
     if (penguin_handle_guest_hypercall(cs, nr, a0, a1, a2, a3, a4, 0, &ret)) {
         return ret;
     }
-    return 0;
+    return a0;
 }
 
 target_ulong helper_csrr(CPURISCVState *env, int csr)