From afe20eb8df9108e4be9bdec88a4f90d2de863ca2 Mon Sep 17 00:00:00 2001 From: Claudio Imbrenda Date: Fri, 11 Nov 2022 18:06:30 +0100 Subject: [PATCH] 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. 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 Reviewed-by: Nico Boehr Reviewed-by: Janosch Frank Reviewed-by: Steffen Eiden Link: https://lore.kernel.org/r/20221111170632.77622-5-imbrenda@linux.ibm.com Message-Id: <20221111170632.77622-5-imbrenda@linux.ibm.com> Signed-off-by: Janosch Frank --- 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 f9810d2..9f18a4a 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; -- 2.7.4