On Fri, Mar 27, 2026 at 01:19:17PM -0700, Jork Loeser wrote: > On L1VH, debugfs stats pages are overlay pages: the kernel allocates > them and registers the GPAs with the hypervisor via > HVCALL_MAP_STATS_PAGE2. These overlay mappings persist in the > hypervisor across kexec. If the kexec'd kernel reuses those physical > pages, the hypervisor's overlay semantics cause a machine check > exception. > > Fix this by calling mshv_debugfs_exit() from the reboot notifier, > which issues HVCALL_UNMAP_STATS_PAGE for each mapped stats page before > kexec. This releases the overlay bindings so the physical pages can be > safely reused. Guard mshv_debugfs_exit() against being called when > init failed. > > Signed-off-by: Jork Loeser <[email protected]> > --- > drivers/hv/mshv_debugfs.c | 7 ++++++- > drivers/hv/mshv_root_main.c | 1 + > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/hv/mshv_debugfs.c b/drivers/hv/mshv_debugfs.c > index ebf2549eb44d..f9a4499cf8f3 100644 > --- a/drivers/hv/mshv_debugfs.c > +++ b/drivers/hv/mshv_debugfs.c > @@ -676,8 +676,10 @@ int __init mshv_debugfs_init(void) > > mshv_debugfs = debugfs_create_dir("mshv", NULL); > if (IS_ERR(mshv_debugfs)) { > + err = PTR_ERR(mshv_debugfs); > + mshv_debugfs = NULL; > pr_err("%s: failed to create debugfs directory\n", __func__); > - return PTR_ERR(mshv_debugfs); > + return err; > } > > if (hv_root_partition()) { > @@ -712,6 +714,9 @@ int __init mshv_debugfs_init(void) > > void mshv_debugfs_exit(void) > { > + if (!mshv_debugfs)
nit: this should allow to avoid setting mshv_debugfs to NULL in the error path of mshv_debugfs_init(): if (!IS_ERR_OR_NULL(mshv_debugfs)) Reviewed-by: Stanislav Kinsburskii <[email protected]> > + return; > + > mshv_debugfs_parent_partition_remove(); > > if (hv_root_partition()) { > diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c > index 281f530b68a9..7038fd830646 100644 > --- a/drivers/hv/mshv_root_main.c > +++ b/drivers/hv/mshv_root_main.c > @@ -2252,6 +2252,7 @@ root_scheduler_deinit(void) > static int mshv_reboot_notify(struct notifier_block *nb, > unsigned long code, void *unused) > { > + mshv_debugfs_exit(); > cpuhp_remove_state(mshv_cpuhp_online); > return 0; > } > -- > 2.43.0 >
