On 3/30/22 14:25, Claudio Imbrenda wrote:
When ptep_get_and_clear_full is called for a mm teardown, we will now
attempt to destroy the secure pages. This will be faster than export.
In case it was not a teardown, or if for some reason the destroy page
UVC failed, we try with an export page, like before.
Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Acked-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
---
arch/s390/include/asm/pgtable.h | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 23ca0d8e058a..72544a1b4a68 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1118,9 +1118,21 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
} else {
res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
}
- /* At this point the reference through the mapping is still present */
- if (mm_is_protected(mm) && pte_present(res))
- uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
+ /* Nothing to do */
+ if (!mm_is_protected(mm) || !pte_present(res))
+ return res;
+ /*
+ * At this point the reference through the mapping is still present.
That's the case because we zap ptes within a mm that's still existing,
right? The mm will be deleted after we have unmapped the memory.
+ * The notifier should have destroyed all protected vCPUs at this
+ * point, so the destroy should be successful.
+ */
+ if (full && !uv_destroy_owned_page(pte_val(res) & PAGE_MASK))
+ return res;
+ /*
+ * But if something went wrong and the pages could not be destroyed,
+ * the slower export is used as fallback instead.
+ */
+ uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
return res;
}
