Use the interval tree to locate an unused range in the VM.
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
Message-Id: <20230707204054.8792-17-richard.hender...@linaro.org>
---
include/exec/cpu-all.h | 15 +++++++++++++++
accel/tcg/user-exec.c | 41 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 56 insertions(+)
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 94f828b109..eb1c54701a 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -236,6 +236,21 @@ int page_check_range(target_ulong start, target_ulong len,
int flags);
*/
bool page_check_range_empty(target_ulong start, target_ulong last);
+/**
+ * page_find_range_empty
+ * @min: first byte of search range
+ * @max: last byte of search range
+ * @len: size of the hole required
+ * @align: alignment of the hole required (power of 2)
+ *
+ * If there is a range [x, x+@len) within [@min, @max] such that
+ * x % @align == 0, then return x. Otherwise return -1.
+ * The memory lock must be held, as the caller will want to ensure
+ * the returned range stays empty until a new mapping can be installed.
+ */
+target_ulong page_find_range_empty(target_ulong min, target_ulong max,
+ target_ulong len, target_ulong align);
+
/**
* page_get_target_data(address)
* @address: guest virtual address
diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
index ab684a3ea2..e4f9563730 100644
--- a/accel/tcg/user-exec.c
+++ b/accel/tcg/user-exec.c
@@ -605,6 +605,47 @@ bool page_check_range_empty(target_ulong start,
target_ulong last)
return pageflags_find(start, last) == NULL;
}
+target_ulong page_find_range_empty(target_ulong min, target_ulong max,
+ target_ulong len, target_ulong align)
+{
+ target_ulong len_m1, align_m1;
+
+ assert(min <= max);
+ assert(max <= GUEST_ADDR_MAX);
+ assert(len != 0);
+ assert(is_power_of_2(align));
+ assert_memory_lock();
+
+ len_m1 = len - 1;
+ align_m1 = align - 1;
+
+ /* Iteratively narrow the search region. */
+ while (1) {
+ PageFlagsNode *p;
+
+ /* Align min and double-check there's enough space remaining. */
+ min = (min + align_m1) & ~align_m1;
+ if (min > max) {
+ return -1;
+ }
+ if (len_m1 > max - min) {
+ return -1;
+ }
+
+ p = pageflags_find(min, min + len_m1);
+ if (p == NULL) {
+ /* Found! */
+ return min;
+ }
+ if (max <= p->itree.last) {
+ /* Existing allocation fills the remainder of the search region. */
+ return -1;
+ }
+ /* Skip across existing allocation. */
+ min = p->itree.last + 1;
+ }
+}
+
void page_protect(tb_page_addr_t address)
{
PageFlagsNode *p;
--
2.34.1
