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Re: [PATCH v14 03/11] target/s390x/cpu topology: handle STSI(15) and bui


From: Pierre Morel
Subject: Re: [PATCH v14 03/11] target/s390x/cpu topology: handle STSI(15) and build the SYSIB
Date: Thu, 19 Jan 2023 14:12:34 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0



On 1/18/23 12:54, Nina Schoetterl-Glausch wrote:
On Wed, 2023-01-18 at 11:26 +0100, Thomas Huth wrote:
On 17/01/2023 17.56, Pierre Morel wrote:


On 1/10/23 15:29, Thomas Huth wrote:
On 05/01/2023 15.53, Pierre Morel wrote:
On interception of STSI(15.1.x) the System Information Block
(SYSIB) is built from the list of pre-ordered topology entries.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
---
...
+typedef struct SysIBTl_container {
+        uint8_t nl;
+        uint8_t reserved[6];
+        uint8_t id;
+} QEMU_PACKED QEMU_ALIGNED(8) SysIBTl_container;
+QEMU_BUILD_BUG_ON(sizeof(SysIBTl_container) != 8);
+
+/* CPU type Topology List Entry */
+typedef struct SysIBTl_cpu {
+        uint8_t nl;
+        uint8_t reserved0[3];
+        uint8_t reserved1:5;
+        uint8_t dedicated:1;
+        uint8_t polarity:2;

Hmmm, yet another bitfield...

Yes, this is the firmware interface.
If it makes problem I can use masks and logic arithmetic

It depends ... if we are sure that this will ever only be used with KVM on
real s390x hardware, then bitfields are OK. If we think that this is
something that could be implemented in TCG, too, I'd scratch the bitfields
and use logic arithmetic instead...

Is there something like linux' bitfield.h in qemu?
In this case it's only two fields, and not too complicated, but I imagine it 
could
get quite ugly to do it manually in other cases.

I'm not too experienced with this CPU topology stuff, but it sounds like it
could be implemented in TCG without too much efforts one day, too, so I'd
rather go with the logic arithmetic immediately instead if it is not too
annoying for you right now.

No problem, I changed all fields to uint8_t and it fits in a uint64_t so I have only a single bit and a single mask to define.


diff --git a/target/s390x/kvm/cpu_topology.c
b/target/s390x/kvm/cpu_topology.c
new file mode 100644
index 0000000000..3831a3264c
--- /dev/null
+++ b/target/s390x/kvm/cpu_topology.c
@@ -0,0 +1,136 @@
+/*
+ * QEMU S390x CPU Topology
+ *
+ * Copyright IBM Corp. 2022

Happy new year?

So after Nina's comment what do I do?
let it be 22 because I started last year or update because what is important
is when it comes into mainline?

Honestly, I don't have a really good clue either... But keeping 2022 is
certainly fine for me, too.

OK then I keep 2022

Regards,

Pierre


--
Pierre Morel
IBM Lab Boeblingen



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