Commit afe20eb8 authored by Claudio Imbrenda's avatar Claudio Imbrenda Committed by Janosch Frank
Browse files

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: default avatarClaudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: default avatarNico Boehr <nrb@linux.ibm.com>
Reviewed-by: default avatarJanosch Frank <frankja@linux.ibm.com>
Reviewed-by: default avatarSteffen Eiden <seiden@linux.ibm.com>
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: default avatarJanosch Frank <frankja@linux.ibm.com>
parent 8c516b25

arch/s390/kernel/uv.c

+7 −0
Original line number Diff line number Diff line
@@ -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;