Re: [PATCH v4 01/15] s390: zcrypt: externalize AP instructions available function

From: Tony Krowiak
Date: Tue Apr 17 2018 - 09:31:16 EST

On 04/16/2018 08:11 AM, Cornelia Huck wrote:
On Mon, 16 Apr 2018 10:44:53 +0200
Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx> wrote:

On 15/04/2018 23:22, Tony Krowiak wrote:
If the AP instructions are not available on the linux host, then
AP devices can not be interpreted by the SIE. The AP bus has a
function it uses to determine if the AP instructions are
available. This patch provides a new function that wraps the
AP bus's function to externalize it for use by KVM.

Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Harald Freudenberger <freude@xxxxxxxxxxxxxxxxxx>
arch/s390/include/asm/ap.h | 7 +++++++
arch/s390/include/asm/kvm-ap.h | 23 +++++++++++++++++++++++
arch/s390/kvm/Makefile | 2 +-
arch/s390/kvm/kvm-ap.c | 21 +++++++++++++++++++++
drivers/s390/crypto/ap_bus.c | 6 ++++++
5 files changed, 58 insertions(+), 1 deletions(-)
create mode 100644 arch/s390/include/asm/kvm-ap.h
create mode 100644 arch/s390/kvm/kvm-ap.c
diff --git a/arch/s390/kvm/kvm-ap.c b/arch/s390/kvm/kvm-ap.c
new file mode 100644
index 0000000..1267588
--- /dev/null
+++ b/arch/s390/kvm/kvm-ap.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0+
+ * Adjunct Processor (AP) configuration management for KVM guests
+ *
+ * Copyright IBM Corp. 2018
+ *
+ * Author(s): Tony Krowiak <akrowia@xxxxxxxxxxxxxxxxxx>
+ */
+#include <linux/kernel.h>
+#include <asm/kvm-ap.h>
+#include <asm/ap.h>
+int kvm_ap_instructions_installed(void)
I did not give my R-B for this.
please change it or suppress my R-B

I think you should review the way you wrap functions
calling the AP interface.
Having all of them together would simplify code and review.
I don't like the ifdeffery either (especially as there's more later).

I'm not crazy about it myself (see below)

Consolidating all functions for querying basic ap capabilities sounds
like a good idea. What about collecting them in a ap-util file and
either always building it or selecting it from both zcrypt and kvm?

My preference would be one of the following:

1. All of the interfaces defined in arch/s390/include/asm/ap.h
are implemented in a file that is built whether ZCRYPT is
built or not.

2. The drivers/s390/crypto/ap_asm.h file containing the functions
that execute the AP instructions are made available outside of
the AP bus, for example; arch/s390/include/asm

I requested this from the maintainer but was told we don't want to
have any crypto adapter support when the host AP functionality is
disabled (CONFIG_ZCRYPT=n). This makes sense, however; I think it is
a bit confusing to have a header file (arch/s390/include/asm/ap.h)
with interfaces that are conditionally built.

This is why I chose the ifdeffery (as you call it) approach. The
only other solution I can conjure is to duplicate the asm code for
the AP instructions needed in KVM and bypass using the AP bus

+ return ap_instructions_installed();
+ return 0;
diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index 35a0c2b..9d108b6 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -210,6 +210,12 @@ int ap_query_configuration(struct ap_config_info *info)

+int ap_instructions_installed(void)
+ return (ap_instructions_available() == 0);
* ap_init_configuration(): Allocate and query configuration array.