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[v1,07/11] KVM: s390: pv: add export before import

Message ID 20210517200758.22593-8-imbrenda@linux.ibm.com (mailing list archive)
State New
Headers show
Series KVM: s390: pv: implement lazy destroy | expand

Commit Message

Claudio Imbrenda May 17, 2021, 8:07 p.m. UTC
Due to upcoming changes, it will be possible to temporarily have
multiple protected VMs in the same address space. When that happens,
it is necessary to perform an export of every page that is to be
imported.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/kernel/uv.c | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Janosch Frank May 26, 2021, 11:56 a.m. UTC | #1
On 5/17/21 10:07 PM, Claudio Imbrenda wrote:
> Due to upcoming changes, it will be possible to temporarily have
> multiple protected VMs in the same address space. When that happens,
> it is necessary to perform an export of every page that is to be
> imported.

... since the Ultravisor doesn't allow KVM to import a secure page
belonging to guest A to be imported for guest B in order to guarantee
proper guest isolation.

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>

> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
>  arch/s390/kernel/uv.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
> index b19b1a1444ec..dbcf4434eb53 100644
> --- a/arch/s390/kernel/uv.c
> +++ b/arch/s390/kernel/uv.c
> @@ -242,6 +242,12 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr,
>  	return rc;
>  }
>  
> +static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm)
> +{
> +	return uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
> +		atomic_read(&mm->context.is_protected) > 1;
> +}
> +
>  /*
>   * Requests the Ultravisor to make a page accessible to a guest.
>   * If it's brought in the first time, it will be cleared. If
> @@ -285,6 +291,8 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb)
>  
>  	lock_page(page);
>  	ptep = get_locked_pte(gmap->mm, uaddr, &ptelock);
> +	if (should_export_before_import(uvcb, gmap->mm))
> +		uv_convert_from_secure(page_to_phys(page));
>  	rc = make_secure_pte(ptep, uaddr, page, uvcb);
>  	pte_unmap_unlock(ptep, ptelock);
>  	unlock_page(page);
>
diff mbox series

Patch

diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index b19b1a1444ec..dbcf4434eb53 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -242,6 +242,12 @@  static int make_secure_pte(pte_t *ptep, unsigned long addr,
 	return rc;
 }
 
+static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm)
+{
+	return uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
+		atomic_read(&mm->context.is_protected) > 1;
+}
+
 /*
  * Requests the Ultravisor to make a page accessible to a guest.
  * If it's brought in the first time, it will be cleared. If
@@ -285,6 +291,8 @@  int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb)
 
 	lock_page(page);
 	ptep = get_locked_pte(gmap->mm, uaddr, &ptelock);
+	if (should_export_before_import(uvcb, gmap->mm))
+		uv_convert_from_secure(page_to_phys(page));
 	rc = make_secure_pte(ptep, uaddr, page, uvcb);
 	pte_unmap_unlock(ptep, ptelock);
 	unlock_page(page);