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

Xiaoyao Li
2023-11-15T07:16:41Z

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@intel.com>
Codeveloped-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
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