diff options
| -rw-r--r-- | arch/s390/kernel/uv.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c index 4c91a3dbc05b..f9810d2a267c 100644 --- a/arch/s390/kernel/uv.c +++ b/arch/s390/kernel/uv.c @@ -234,6 +234,32 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr, return uvcb->rc == 0x10a ? -ENXIO : -EINVAL; } +/** + * should_export_before_import - Determine whether an export is needed + * before an import-like operation + * @uvcb: the Ultravisor control block of the UVC to be performed + * @mm: the mm of the process + * + * Returns whether an export is needed before every import-like operation. + * This is needed for shared pages, which don't trigger a secure storage + * exception when accessed from a different guest. + * + * Although considered as one, the Unpin Page UVC is not an actual import, + * so it is not affected. + * + * No export is needed also when there is only one protected VM, because the + * page cannot belong to the wrong VM in that case (there is no "other VM" + * it can belong to). + * + * Return: true if an export is needed before every import, otherwise false. + */ +static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm) +{ + if (uvcb->cmd == UVC_CMD_UNPIN_PAGE_SHARED) + return false; + return atomic_read(&mm->context.protected_count) > 1; +} + /* * Requests the Ultravisor to make a page accessible to a guest. * If it's brought in the first time, it will be cleared. If @@ -277,6 +303,8 @@ again: lock_page(page); ptep = get_locked_pte(gmap->mm, uaddr, &ptelock); + if (should_export_before_import(uvcb, gmap->mm)) + uv_convert_from_secure(page_to_phys(page)); rc = make_secure_pte(ptep, uaddr, page, uvcb); pte_unmap_unlock(ptep, ptelock); unlock_page(page); |