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_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
