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Message-Id: <20220302181143.188283-12-imbrenda@linux.ibm.com>
Date: Wed, 2 Mar 2022 19:11:37 +0100
From: Claudio Imbrenda <imbrenda@...ux.ibm.com>
To: kvm@...r.kernel.org
Cc: borntraeger@...ibm.com, frankja@...ux.ibm.com, thuth@...hat.com,
pasic@...ux.ibm.com, david@...hat.com, linux-s390@...r.kernel.org,
linux-kernel@...r.kernel.org, scgl@...ux.ibm.com,
mimu@...ux.ibm.com, nrb@...ux.ibm.com
Subject: [PATCH v8 11/17] s390/mm: KVM: pv: when tearing down, try to destroy protected pages
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@...ux.ibm.com>
Acked-by: Janosch Frank <frankja@...ux.ibm.com>
---
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.
+ * 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;
}
--
2.34.1
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