From: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> If the appropriate UV feature bit is set, there is no need to perform an export before import. The misc feature indicates, among other things, that importing a shared page from a different protected VM will automatically also transfer its ownership. Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> Reviewed-by: Nico Boehr <nrb@xxxxxxxxxxxxx> Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx> Reviewed-by: Steffen Eiden <seiden@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20221111170632.77622-5-imbrenda@xxxxxxxxxxxxx Message-Id: <20221111170632.77622-5-imbrenda@xxxxxxxxxxxxx> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx> --- arch/s390/kernel/uv.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c index f9810d2a267c..9f18a4af9c13 100644 --- a/arch/s390/kernel/uv.c +++ b/arch/s390/kernel/uv.c @@ -255,6 +255,13 @@ 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) { + /* + * The misc feature indicates, among other things, that importing a + * shared page from a different protected VM will automatically also + * transfer its ownership. + */ + 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; -- 2.38.1
