On Mon, Apr 27, 2026 at 02:38:54PM -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]>
Reviewed-by: Stanislav Kinsburskii <[email protected]> > --- > drivers/hv/mshv_debugfs.c | 7 ++++++- > drivers/hv/mshv_synic.c | 1 + > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/hv/mshv_debugfs.c b/drivers/hv/mshv_debugfs.c > index 418b6dc8f3c2..3c3e02237ae9 100644 > --- a/drivers/hv/mshv_debugfs.c > +++ b/drivers/hv/mshv_debugfs.c > @@ -674,8 +674,10 @@ 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()) { > @@ -710,6 +712,9 @@ int __init mshv_debugfs_init(void) > > void mshv_debugfs_exit(void) > { > + if (!mshv_debugfs) > + return; > + > mshv_debugfs_parent_partition_remove(); > > if (hv_root_partition()) { > diff --git a/drivers/hv/mshv_synic.c b/drivers/hv/mshv_synic.c > index 978a1cace341..88170ce6b83f 100644 > --- a/drivers/hv/mshv_synic.c > +++ b/drivers/hv/mshv_synic.c > @@ -723,6 +723,7 @@ mshv_unregister_doorbell(u64 partition_id, int > doorbell_portid) > static int mshv_synic_reboot_notify(struct notifier_block *nb, > unsigned long code, void *unused) > { > + mshv_debugfs_exit(); > cpuhp_remove_state(synic_cpuhp_online); > return 0; > } > -- > 2.43.0 >
