[PATCH v3 09/70] physmem: Introduce ram_block_convert_range() for page conversion

[Xiaoyao Li <xiaoyao.li@xxxxxxxxx>]

It's used for discarding opposite memory after memory conversion, for
confidential guest.

When page is converted from shared to private, the original shared
memory can be discarded via ram_block_discard_range();

When page is converted from private to shared, the original private
memory is back'ed by guest_memfd. Introduce
ram_block_discard_guest_memfd_range() for discarding memory in
guest_memfd.

Originally-from: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Codeveloped-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
---
 include/exec/cpu-common.h |  2 ++
 system/physmem.c          | 50 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 41115d891940..de728a18eef2 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -175,6 +175,8 @@ typedef int (RAMBlockIterFunc)(RAMBlock *rb, void *opaque);
 
 int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque);
 int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length);
+int ram_block_convert_range(RAMBlock *rb, uint64_t start, size_t length,
+                            bool shared_to_private);
 
 #endif
 
diff --git a/system/physmem.c b/system/physmem.c
index ddfecddefcd6..cd6008fa09ad 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -3641,6 +3641,29 @@ err:
     return ret;
 }
 
+static int ram_block_discard_guest_memfd_range(RAMBlock *rb, uint64_t start,
+                                               size_t length)
+{
+    int ret = -1;
+
+#ifdef CONFIG_FALLOCATE_PUNCH_HOLE
+    ret = fallocate(rb->guest_memfd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+                    start, length);
+
+    if (ret) {
+        ret = -errno;
+        error_report("%s: Failed to fallocate %s:%" PRIx64 " +%zx (%d)",
+                     __func__, rb->idstr, start, length, ret);
+    }
+#else
+    ret = -ENOSYS;
+    error_report("%s: fallocate not available %s:%" PRIx64 " +%zx (%d)",
+                 __func__, rb->idstr, start, length, ret);
+#endif
+
+    return ret;
+}
+
 bool ramblock_is_pmem(RAMBlock *rb)
 {
     return rb->flags & RAM_PMEM;
@@ -3828,3 +3851,30 @@ bool ram_block_discard_is_required(void)
     return qatomic_read(&ram_block_discard_required_cnt) ||
            qatomic_read(&ram_block_coordinated_discard_required_cnt);
 }
+
+int ram_block_convert_range(RAMBlock *rb, uint64_t start, size_t length,
+                            bool shared_to_private)
+{
+    if (!rb || rb->guest_memfd < 0) {
+        return -1;
+    }
+
+    if (!QEMU_PTR_IS_ALIGNED(start, qemu_host_page_size) ||
+        !QEMU_PTR_IS_ALIGNED(length, qemu_host_page_size)) {
+        return -1;
+    }
+
+    if (!length) {
+        return -1;
+    }
+
+    if (start + length > rb->max_length) {
+        return -1;
+    }
+
+    if (shared_to_private) {
+        return ram_block_discard_range(rb, start, length);
+    } else {
+        return ram_block_discard_guest_memfd_range(rb, start, length);
+    }
+}
-- 
2.34.1