Messages in this thread Patch in this message | | | From | Claudio Imbrenda <> | Subject | [PATCH v15 4/6] KVM: s390: pv: avoid export before import if possible | Date | Mon, 10 Oct 2022 16:54:40 +0200 |
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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@linux.ibm.com> Reviewed-by: Nico Boehr <nrb@linux.ibm.com> Reviewed-by: Janosch Frank <frankja@linux.ibm.com> Reviewed-by: Steffen Eiden <seiden@linux.ibm.com> --- 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; -- 2.37.3
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