linux-kernel - [PATCH v13 4/6] KVM: s390: pv: avoid export before import if possible

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Message-Id: <20220810125625.45295-5-imbrenda@linux.ibm.com>
Date:   Wed, 10 Aug 2022 14:56:23 +0200
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,
        seiden@...ux.ibm.com, nrb@...ux.ibm.com
Subject: [PATCH v13 4/6] KVM: s390: pv: avoid export before import if possible

If the appropriate UV feature bit is set, there is no need to perform
an export before import.

Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
Reviewed-by: Nico Boehr <nrb@...ux.ibm.com>
---
 arch/s390/kernel/uv.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index f9810d2a267c..b455646c8d74 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -255,6 +255,8 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr,
  */
 static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm)
 {
+	if (test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications))
+		return false;
 	if (uvcb->cmd == UVC_CMD_UNPIN_PAGE_SHARED)
 		return false;
 	return atomic_read(&mm->context.protected_count) > 1;
-- 
2.37.1