[PULL 20/37] hw/s390x/ipl: Rework s390_ipl_map_iplb_chain for certificate storage

[Eric Farman <farman@linux.ibm.com>]

From: Zhuoying Cai <zycai@linux.ibm.com>

Rework s390_ipl_map_iplb_chain to always allocate maximum memory for
the IPLB chain, regardless of the number of boot devices. This space
is also used to store certificates during secure boot, providing a
safe location for certificates until the kernel reads them during boot.

Rename next_iplb to ipl_data to better reflect its multiple purposes:
storing both IPLB chains and certificate data.

Signed-off-by: Zhuoying Cai <zycai@linux.ibm.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Link: https://lore.kernel.org/qemu-devel/20260730214624.2328883-19-zycai@linux.ibm.com
Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
 hw/s390x/ipl.c              | 18 ++++++++++++++----
 hw/s390x/ipl.h              |  2 --
 include/hw/s390x/ipl/qipl.h |  5 ++++-
 pc-bios/s390-ccw/iplb.h     |  4 ++--
 4 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
index 627544b361..85fe2d3cb4 100644
--- a/hw/s390x/ipl.c
+++ b/hw/s390x/ipl.c
@@ -426,10 +426,9 @@ static S390PCIBusDevice *s390_get_pci_device(DeviceState *dev_st, int *devtype)
     return pbdev;
 }
 
-static uint64_t s390_ipl_map_iplb_chain(IplParameterBlock *iplb_chain)
+static uint64_t s390_ipl_map_iplb_chain(IplParameterBlock *iplb_chain, uint16_t count)
 {
     S390IPLState *ipl = get_ipl_device();
-    uint16_t count = be16_to_cpu(ipl->qipl.chain_len);
     uint64_t len = sizeof(IplParameterBlock) * count;
     uint64_t chain_addr = find_iplb_chain_addr(ipl->bios_start_addr, count);
 
@@ -593,7 +592,7 @@ void s390_rebuild_iplb(uint16_t dev_index, IplParameterBlock *iplb)
 static bool s390_init_all_iplbs(S390IPLState *ipl)
 {
     int iplb_num = 0;
-    IplParameterBlock iplb_chain[7];
+    IplParameterBlock iplb_chain[MAX_BOOT_DEVS - 1] = { 0 };
     DeviceState *dev_st = get_boot_device(0);
     Object *machine = qdev_get_machine();
 
@@ -639,13 +638,24 @@ static bool s390_init_all_iplbs(S390IPLState *ipl)
             dev_st = get_boot_device(i);
             s390_build_iplb(dev_st, &iplb_chain[i - 1]);
         }
+    }
 
-        ipl->qipl.next_iplb = cpu_to_be64(s390_ipl_map_iplb_chain(iplb_chain));
+    /*
+     * Allocate maximum space for IPLB chain and/or certificate storage.
+     * Once a valid boot device is found, this space will be used to store
+     * certificates if secure boot is enabled.
+     */
+    if (iplb_num > 1 || s390_has_certificate()) {
+        ipl->qipl.ipl_data = cpu_to_be64(s390_ipl_map_iplb_chain(iplb_chain,
+                                                                 MAX_BOOT_DEVS - 1));
     }
 
     return iplb_num;
 }
 
+QEMU_BUILD_BUG_MSG(sizeof(IplParameterBlock) * (MAX_BOOT_DEVS - 1) != CERT_BUF_SIZE,
+                   "certificate buffer size is wrong");
+
 static void update_machine_ipl_properties(IplParameterBlock *iplb)
 {
     Object *machine = qdev_get_machine();
diff --git a/hw/s390x/ipl.h b/hw/s390x/ipl.h
index 5d54827b52..772566bb11 100644
--- a/hw/s390x/ipl.h
+++ b/hw/s390x/ipl.h
@@ -23,8 +23,6 @@
 #include "qom/object.h"
 #include "target/s390x/kvm/pv.h"
 
-#define MAX_BOOT_DEVS 8 /* Max number of devices that may have a bootindex */
-
 void s390_ipl_convert_loadparm(char *ascii_lp, uint8_t *ebcdic_lp);
 void s390_ipl_fmt_loadparm(uint8_t *loadparm, char *str, Error **errp);
 void s390_rebuild_iplb(uint16_t index, IplParameterBlock *iplb);
diff --git a/include/hw/s390x/ipl/qipl.h b/include/hw/s390x/ipl/qipl.h
index 6dccc74a9e..5d560a433a 100644
--- a/include/hw/s390x/ipl/qipl.h
+++ b/include/hw/s390x/ipl/qipl.h
@@ -43,7 +43,10 @@ typedef enum S390IplType S390IplType;
 #define S390_IPLB_MIN_QEMU_SCSI_LEN 200
 #define S390_IPLB_MAX_LEN 4096
 
+#define MAX_BOOT_DEVS 8 /* Max number of devices that may have a bootindex */
+
 #define MAX_CERTIFICATES  64
+#define CERT_BUF_SIZE     ((MAX_BOOT_DEVS - 1) * 4096)
 /* largest supported block size - same as VIRTIO_DASD_DEFAULT_BLOCK_SIZE */
 #define VIRTIO_MAX_BLOCK_SIZE   4096
 #define MAX_COMP_ENTRIES        ((VIRTIO_MAX_BLOCK_SIZE - 32) / 32)
@@ -63,7 +66,7 @@ struct QemuIplParameters {
     uint32_t boot_menu_timeout;
     uint8_t  reserved3[2];
     uint16_t chain_len;
-    uint64_t next_iplb;
+    uint64_t ipl_data;
 } QEMU_PACKED;
 typedef struct QemuIplParameters QemuIplParameters;
 
diff --git a/pc-bios/s390-ccw/iplb.h b/pc-bios/s390-ccw/iplb.h
index c92a3d0f0c..c807e7f49b 100644
--- a/pc-bios/s390-ccw/iplb.h
+++ b/pc-bios/s390-ccw/iplb.h
@@ -61,11 +61,11 @@ static inline bool load_next_iplb(void)
     }
 
     qipl.index++;
-    next_iplb = (IplParameterBlock *) qipl.next_iplb;
+    next_iplb = (IplParameterBlock *) qipl.ipl_data;
     memcpy(iplb, next_iplb, sizeof(IplParameterBlock));
 
     qipl.chain_len--;
-    qipl.next_iplb = qipl.next_iplb + sizeof(IplParameterBlock);
+    qipl.ipl_data = qipl.ipl_data + sizeof(IplParameterBlock);
 
     return true;
 }
-- 
2.55.0