I talked with the firmware guys about this.
The answer is that the AP 3 instructions (NQAP, DQAP, PQAP) are always available.
Tony is right with the facility bits.
facility bit 15 tells if the T bit is supported with the PQAP(TAPQ) subcommand,
facility bit 12 tells if the PQAP(QCI) subcommand is available.
As far as I could discover the AP instructions where optional on some older machines.
This may be the reason why zVM throws an exception if there is no AP device assigned.
However, for all machines still in service the AP instructions are available at al time.
Mit freundlichen Grüßen / Kind regards
Harald Freudenberger
IBM Systems &Technology Group, zLinux Development
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Tony Krowiak ---02.11.2017 16:36:38---On 11/02/2017 08:08 AM, Christian Borntraeger wrote: >
From: Tony Krowiak <address@hidden>
To: address@hidden, address@hidden, Harald Freudenberger/Germany/address@hidden
Cc: address@hidden, address@hidden, address@hidden, address@hidden, address@hidden, address@hidden, address@hidden, address@hidden, address@hidden, address@hidden, address@hidden, address@hidden, address@hidden, address@hidden, address@hidden, address@hidden
Date: 02.11.2017 16:36
Subject: Re: [RFC 19/19] s390/facilities: enable AP facilities needed by guest
On 11/02/2017 08:08 AM, Christian Borntraeger wrote:
On 10/16/2017 11:25 AM, Martin Schwidefsky wrote:
- On Fri, 13 Oct 2017 13:39:04 -0400
Tony Krowiak <address@hidden> wrote:
- Sets up the following facilities bits to enable the specified AP
facilities for the guest VM:
* STFLE.12: Enables the AP Query Configuration Information
facility. The AP bus running in the guest uses
the information returned from this instruction
to configure AP adapters and domains for the
guest machine.
* STFLE.15: Indicates the AP facilities test is available.
The AP bus running in the guest uses the
information.
Signed-off-by: Tony Krowiak <address@hidden>
---
arch/s390/tools/gen_facilities.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/arch/s390/tools/gen_facilities.c b/arch/s390/tools/gen_facilities.c
index 70dd8f1..eeaa7db 100644
--- a/arch/s390/tools/gen_facilities.c
+++ b/arch/s390/tools/gen_facilities.c
@@ -74,8 +74,10 @@ struct facility_def {
8, /* enhanced-DAT 1 */
9, /* sense-running-status */
10, /* conditional sske */
+ 12, /* AP query configuration */
13, /* ipte-range */
14, /* nonquiescing key-setting */
+ 15, /* AP special-command facility */
73, /* transactional execution */
75, /* access-exception-fetch/store indication */
76, /* msa extension 3 */
With this all KVM guests will always have the AP instructions available, no?
In principles I like this approach, but it differs from the way z/VM does things,
there the guest will get an exception if it tries to execute an AP instruction
if there are no AP devices assigned to the guest. I wonder if there is a reason
why z/VM does it the way it does.
A good question. For LPAR it seems that you have AP instructions even if you have
no crypto cards.
to the guest. Bit 12 controls whether the PQAP(QCI) - query AP configuration information - instruction
is available. This is necessary because if the PQAP(QCI) instruction is not available to the guest,
then the AP bus scan code running on the guest will not create any AP devices regardless of whether
AP devices are assigned to the guest or not. Facility bit 15 indicates whether the APFT facility is
installed. If the APFT facility is not installed, then it looks like the probe function for CEX4 and
CEX5 cards will fail because the information provided by the facility will not be returned from the
PQAP(TAPQ) function.
The way the AP bus determines whether or not AP instructions are installed is by executing an AP
instruction. If the instruction throws an exception, then it is assumed the AP instructions are not
available. This is done in the AP module init which returns -ENODEV if the AP instructions are not
installed. Since the AP bus is not initialized, no AP instructions will ever get executed. I surmise
this is the difference between z/VM and linux.
Harald, can you verify my statements above?