2022-08-10 13:14:15

by Claudio Imbrenda

Subject: [PATCH v13 4/6] 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.

Signed-off-by: Claudio Imbrenda <[email protected]>
Reviewed-by: Nico Boehr <[email protected]>
---
arch/s390/kernel/uv.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index f9810d2a267c..b455646c8d74 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -255,6 +255,8 @@ 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)
{
+ 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;
--
2.37.1

2022-08-19 09:57:26

by Janosch Frank

Subject: Re: [PATCH v13 4/6] KVM: s390: pv: avoid export before import if possible

On 8/10/22 14:56, Claudio Imbrenda wrote:
> If the appropriate UV feature bit is set, there is no need to perform
> an export before import.
>
> Signed-off-by: Claudio Imbrenda <[email protected]>
> Reviewed-by: Nico Boehr <[email protected]>
> ---
> arch/s390/kernel/uv.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
> index f9810d2a267c..b455646c8d74 100644
> --- a/arch/s390/kernel/uv.c
> +++ b/arch/s390/kernel/uv.c
> @@ -255,6 +255,8 @@ 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)
> {
The misc feature indicates that the UV will automatically transfer
ownership from one protected VM to another when importing a shared page.


Other than that:
Reviewed-by: Janosch Frank <[email protected]>


> + 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;