1 files changed, 27 insertions, 0 deletions

diff --git a/gitlab/issues/target_missing/host_missing/accel_missing/1638.toml b/gitlab/issues/target_missing/host_missing/accel_missing/1638.toml
new file mode 100644
index 00000000..54aa80a5
--- /dev/null
+++ b/gitlab/issues/target_missing/host_missing/accel_missing/1638.toml
@@ -0,0 +1,27 @@
+id = 1638
+title = "BUG: Segmentation fault when -object memory-backend-file use readonly=on, prealloc=on together"
+state = "opened"
+created_at = "2023-05-07T16:04:44.630Z"
+closed_at = "n/a"
+labels = []
+url = "https://gitlab.com/qemu-project/qemu/-/issues/1638"
+host-os = "Ubuntu 20.04 LTS"
+host-arch = "x86_64"
+qemu-version = "7"
+guest-os = "Ubuntu20.04LTS"
+guest-arch = "x86_64"
+description = """Segmentation Fault while booting VM."""
+reproduce = """1. set qemu boot params to `-object memory-backend-file,id=mem1,readonly=on,prealloc=on,mem-path=<any-img-file>,size=4G`
+2.
+3."""
+additional = """It might not be a bug, probably a feature.
+The reason of this segfault is:
+readonly would mmap the backend file using PROT_READ, make it readonly,
+but the prealloc=on would touch_pages the memory mmaped by the file.
+SO the segfault happens.
+
+But there is no docs about this segfault condition (the readonly and prealloc cannot be used together.)
+
+And maybe there is a way to solve this problem, I think.
+Use mmap the memory backend file to PROT_READ|PROT_WRITE at the beginnning, after touch_pages, then mprotect the memory.
+change the prot to readonly if required."""