s390-ccw: move auxiliary IPL data to separate location

The s390-ccw firmware needs some information in support of the
boot process which is not available on the native machine.
Examples are the netboot firmware load address and now the
boot menu parameters.

While storing that data in unused fields of the IPL parameter block
works, that approach could create problems if the parameter block
definition should change in the future. Because then a guest could
overwrite these fields using the set IPLB diagnose.

In fact the data in question is of more global nature and not really
tied to an IPL device, so separating it is rather logical.

This commit introduces a new structure to hold firmware relevant
IPL parameters set by QEMU. The data is stored at location 204 (dec)
and can contain up to 7 32-bit words. This area is available to
programming in the z/Architecture Principles of Operation and
can thus safely be used by the firmware until the IPL has completed.

Signed-off-by: Viktor Mihajlovski <mihajlov@linux.vnet.ibm.com>
Signed-off-by: Collin L. Walling <walling@linux.vnet.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
[thuth: fixed "4 + 8 * n" comment]
Signed-off-by: Thomas Huth <thuth@redhat.com>

2 files changed, 40 insertions, 3 deletions

diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
index 0d06fc1..79f5a58 100644
--- a/hw/s390x/ipl.c
+++ b/hw/s390x/ipl.c
@@ -399,6 +399,21 @@ void s390_reipl_request(void)
     qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
 }
 
+static void s390_ipl_prepare_qipl(S390CPU *cpu)
+{
+    S390IPLState *ipl = get_ipl_device();
+    uint8_t *addr;
+    uint64_t len = 4096;
+
+    addr = cpu_physical_memory_map(cpu->env.psa, &len, 1);
+    if (!addr || len < QIPL_ADDRESS + sizeof(QemuIplParameters)) {
+        error_report("Cannot set QEMU IPL parameters");
+        return;
+    }
+    memcpy(addr + QIPL_ADDRESS, &ipl->qipl, sizeof(QemuIplParameters));
+    cpu_physical_memory_unmap(addr, len, 1, len);
+}
+
 void s390_ipl_prepare_cpu(S390CPU *cpu)
 {
     S390IPLState *ipl = get_ipl_device();
@@ -418,8 +433,9 @@ void s390_ipl_prepare_cpu(S390CPU *cpu)
             error_report_err(err);
             vm_stop(RUN_STATE_INTERNAL_ERROR);
         }
-        ipl->iplb.ccw.netboot_start_addr = cpu_to_be64(ipl->start_addr);
+        ipl->qipl.netboot_start_addr = cpu_to_be64(ipl->start_addr);
     }
+    s390_ipl_prepare_qipl(cpu);
 }
 
 static void s390_ipl_reset(DeviceState *dev)
diff --git a/hw/s390x/ipl.h b/hw/s390x/ipl.h
index 8a705e0..5cc3b77 100644
--- a/hw/s390x/ipl.h
+++ b/hw/s390x/ipl.h
@@ -16,8 +16,7 @@
 #include "cpu.h"
 
 struct IplBlockCcw {
-    uint64_t netboot_start_addr;
-    uint8_t  reserved0[77];
+    uint8_t  reserved0[85];
     uint8_t  ssid;
     uint16_t devno;
     uint8_t  vm_flags;
@@ -90,6 +89,27 @@ void s390_ipl_prepare_cpu(S390CPU *cpu);
 IplParameterBlock *s390_ipl_get_iplb(void);
 void s390_reipl_request(void);
 
+#define QIPL_ADDRESS  0xcc
+
+/*
+ * The QEMU IPL Parameters will be stored at absolute address
+ * 204 (0xcc) which means it is 32-bit word aligned but not
+ * double-word aligned.
+ * Placement of data fields in this area must account for
+ * their alignment needs. E.g., netboot_start_address must
+ * have an offset of 4 + n * 8 bytes within the struct in order
+ * to keep it double-word aligned.
+ * The total size of the struct must never exceed 28 bytes.
+ * This definition must be kept in sync with the defininition
+ * in pc-bios/s390-ccw/iplb.h.
+ */
+struct QemuIplParameters {
+    uint8_t  reserved1[4];
+    uint64_t netboot_start_addr;
+    uint8_t  reserved2[16];
+} QEMU_PACKED;
+typedef struct QemuIplParameters QemuIplParameters;
+
 #define TYPE_S390_IPL "s390-ipl"
 #define S390_IPL(obj) OBJECT_CHECK(S390IPLState, (obj), TYPE_S390_IPL)
 
@@ -105,6 +125,7 @@ struct S390IPLState {
     bool iplb_valid;
     bool reipl_requested;
     bool netboot;
+    QemuIplParameters qipl;
 
     /*< public >*/
     char *kernel;