[PATCH v6 11/17] s390/mm: KVM: pv: when tearing down, try to destroy protected pages

Claudio Imbrenda
2021-12-03T16:59:13Z

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@linux.ibm.com>
---
arch/s390/include/asm/pgtable.h | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 23ca0d8e058a..c008b354573e 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1118,9 +1118,14 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
} else {
res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
}
+ /* Nothing to do */
+ if (!mm_is_protected(mm) || !pte_present(res))
+ return res;
/* 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);
+ if (full && !uv_destroy_owned_page(pte_val(res) & PAGE_MASK))
+ return res;
+ /* If could not destroy, we try export */
+ uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
return res;
}

--
2.31.1