[PATCH v10 18/19] KVM: s390: pv: avoid export before import if possible

From: Claudio Imbrenda
Date: Thu Apr 14 2022 - 04:05:01 EST


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

Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
---
arch/s390/kernel/uv.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index e358b8bd864b..43393568f844 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -236,7 +236,8 @@ 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)
{
- return uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
+ return !test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications) &&
+ uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
atomic_read(&mm->context.protected_count) > 1;
}

--
2.34.1