On 9/12/23 16:50, Dmitry Frolov wrote:
According to previous statement, 'free_mem' is less than 'needed_mem'. So, the subtraction 'free_mem - needed_mem' is negative, and will raise uint64 underflow.
Signed-off-by: Dmitry Frolov <frolov@swemel.ru> --- src/libxl/libxl_domain.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c index 6c167df63e..36be042971 100644 --- a/src/libxl/libxl_domain.c +++ b/src/libxl/libxl_domain.c @@ -940,7 +940,7 @@ libxlDomainFreeMem(libxl_ctx *ctx, libxl_domain_config *d_config) if (free_mem >= needed_mem) return 0;
- target_mem = free_mem - needed_mem; + target_mem = needed_mem - free_mem; if (libxlSetMemoryTargetWrapper(ctx, 0, target_mem, /* relative */ 1, 0) < 0) goto error;
Yeah, this fixes the underflow, but I worry about the while semantics a bit. What the code effectively does: libxl_domain_need_memory(&needed_mem); do { libxl_get_free_memory(&free_mem); if (free_mem >= needed_mem) return 0; target_mem = needed_mem - free_mem; libxl_set_memory_target(target_mem); } while(...) Now, if libxl_domain_need_memory() returns how much memory a domain really needs, then why undergo trouble of getting its free memory? Why not pass it to set_memory_target() right away? Or am I misunderstanding something? Michal