Let's add a way to return the value (successfully) set via
s390_set_max_pagesize() previously. This will be helpful to reject
hotplugged memory devices that would exceed this initially set page size.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 target/s390x/cpu-sysemu.c | 16 ++++++++++++++++
 target/s390x/cpu.h        |  1 +
 2 files changed, 17 insertions(+)

diff --git a/target/s390x/cpu-sysemu.c b/target/s390x/cpu-sysemu.c
index 1915567b3a..bee5d6c2ee 100644
--- a/target/s390x/cpu-sysemu.c
+++ b/target/s390x/cpu-sysemu.c
@@ -278,11 +278,27 @@ uint64_t s390_get_memory_limit(void)
     return memory_limit;
 }
 
+static uint64_t max_pagesize;
+
 void s390_set_max_pagesize(uint64_t pagesize, Error **errp)
 {
+    ERRP_GUARD();
+
+    if (max_pagesize) {
+        error_setg(errp, "Maximum page size can only be set once");
+        return;
+    }
     if (kvm_enabled()) {
         kvm_s390_set_max_pagesize(pagesize, errp);
     }
+    if (!*errp) {
+        max_pagesize = pagesize;
+    }
+}
+
+uint64_t s390_get_max_pagesize(void)
+{
+    return max_pagesize;
 }
 
 void s390_cmma_reset(void)
diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
index 7a51b606ed..37845e0d9d 100644
--- a/target/s390x/cpu.h
+++ b/target/s390x/cpu.h
@@ -897,6 +897,7 @@ void s390_crypto_reset(void);
 int s390_set_memory_limit(uint64_t new_limit, uint64_t *hw_limit);
 uint64_t s390_get_memory_limit(void);
 void s390_set_max_pagesize(uint64_t pagesize, Error **errp);
+uint64_t s390_get_max_pagesize(void);
 void s390_cmma_reset(void);
 void s390_enable_css_support(S390CPU *cpu);
 void s390_do_cpu_set_diag318(CPUState *cs, run_on_cpu_data arg);
-- 
2.46.0

On 10.09.24 19:58, David Hildenbrand wrote:
> Let's add a way to return the value (successfully) set via
> s390_set_max_pagesize() previously. This will be helpful to reject
> hotplugged memory devices that would exceed this initially set page size.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---

I'll send a v2 shortly, this patch will become:

 From 687f72e488ebed59e57793699d26feb4eebdc9e3 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <david@redhat.com>
Date: Sun, 8 Sep 2024 23:25:27 +0200
Subject: [PATCH] s390x: remember the maximum page size

Let's remember the value (successfully) set via s390_set_max_pagesize().
This will be helpful to reject hotplugged memory devices that would exceed
this initially set page size.

Handle it just like how we handle s390_get_memory_limit(), storing it in
the machine, and moving the handling to machine code.

Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
  hw/s390x/s390-virtio-ccw.c         | 12 +++++++++++-
  include/hw/s390x/s390-virtio-ccw.h |  1 +
  target/s390x/cpu-sysemu.c          |  7 -------
  target/s390x/cpu.h                 |  1 -
  4 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 2031c4cf29..65f266a78f 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -150,6 +150,16 @@ uint64_t s390_get_memory_limit(S390CcwMachineState *s390ms)
      return s390ms->memory_limit;
  }
  
+static void s390_set_max_pagesize(S390CcwMachineState *s390ms,
+                                  uint64_t pagesize)
+{
+    assert(!s390ms->max_pagesize && pagesize);
+    if (kvm_enabled()) {
+        kvm_s390_set_max_pagesize(pagesize, &error_fatal);
+    }
+    s390ms->max_pagesize = pagesize;
+}
+
  static void s390_memory_init(MachineState *machine)
  {
      S390CcwMachineState *s390ms = S390_CCW_MACHINE(machine);
@@ -198,7 +208,7 @@ static void s390_memory_init(MachineState *machine)
       * Configure the maximum page size. As no memory devices were created
       * yet, this is the page size of initial memory only.
       */
-    s390_set_max_pagesize(qemu_maxrampagesize(), &error_fatal);
+    s390_set_max_pagesize(s390ms, qemu_maxrampagesize());
      /* Initialize storage key device */
      s390_skeys_init();
      /* Initialize storage attributes device */
diff --git a/include/hw/s390x/s390-virtio-ccw.h b/include/hw/s390x/s390-virtio-ccw.h
index eb04542979..5a730f5d07 100644
--- a/include/hw/s390x/s390-virtio-ccw.h
+++ b/include/hw/s390x/s390-virtio-ccw.h
@@ -30,6 +30,7 @@ struct S390CcwMachineState {
      bool pv;
      uint8_t loadparm[8];
      uint64_t memory_limit;
+    uint64_t max_pagesize;
  
      SCLPDevice *sclp;
  };
diff --git a/target/s390x/cpu-sysemu.c b/target/s390x/cpu-sysemu.c
index 3118a25fee..706a5c53e2 100644
--- a/target/s390x/cpu-sysemu.c
+++ b/target/s390x/cpu-sysemu.c
@@ -255,13 +255,6 @@ unsigned int s390_cpu_set_state(uint8_t cpu_state, S390CPU *cpu)
      return s390_count_running_cpus();
  }
  
-void s390_set_max_pagesize(uint64_t pagesize, Error **errp)
-{
-    if (kvm_enabled()) {
-        kvm_s390_set_max_pagesize(pagesize, errp);
-    }
-}
-
  void s390_cmma_reset(void)
  {
      if (kvm_enabled()) {
diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
index b4506539f0..5b7992deda 100644
--- a/target/s390x/cpu.h
+++ b/target/s390x/cpu.h
@@ -881,7 +881,6 @@ static inline void s390_do_cpu_load_normal(CPUState *cs, run_on_cpu_data arg)
  
  /* cpu.c */
  void s390_crypto_reset(void);
-void s390_set_max_pagesize(uint64_t pagesize, Error **errp);
  void s390_cmma_reset(void);
  void s390_enable_css_support(S390CPU *cpu);
  void s390_do_cpu_set_diag318(CPUState *cs, run_on_cpu_data arg);
-- 
2.46.1



-- 
Cheers,

David / dhildenb