From ddfee9d393af322938e4df466cd01b8f9570a1c9 Mon Sep 17 00:00:00 2001
From: Thomas Huth <thuth@redhat.com>
Date: Tue, 5 Apr 2022 10:20:59 +0200
Subject: [PATCH 1/6] s390x/ipl: support extended kernel command line size

RH-Author: Thomas Huth <thuth@redhat.com>
RH-MergeRequest: 144: s390x/ipl: support extended kernel command line size
RH-Commit: [1/1] be227e50af5dbe7802605f873db29ac5358aa196
RH-Bugzilla: 2043830
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>

Bugzilla: http://bugzilla.redhat.com/2043830

commit b2173046a64beed76715f310f98538f159276af1
Author: Marc Hartmayer <mhartmay@linux.ibm.com>
Date:   Mon Nov 22 12:29:09 2021 +0100

    s390x/ipl: support extended kernel command line size

    In the past s390 used a fixed command line length of 896 bytes. This has changed
    with the Linux commit 5ecb2da660ab ("s390: support command lines longer than 896
    bytes"). There is now a parm area indicating the maximum command line size. This
    parm area has always been initialized to zero, so with older kernels this field
    would read zero and we must then assume that only 896 bytes are available.

    Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
    Reviewed-by: David Hildenbrand <david@redhat.com>
    Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
    Acked-by: Viktor Mihajlovski <mihajlov@de.ibm.com>
    Message-Id: <20211122112909.18138-1-mhartmay@linux.ibm.com>
    [thuth: Cosmetic fixes, and use PRIu64 instead of %lu]
    Signed-off-by: Thomas Huth <thuth@redhat.com>

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 hw/s390x/ipl.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
index 7ddca0127f..eb7fc4c4ae 100644
--- a/hw/s390x/ipl.c
+++ b/hw/s390x/ipl.c
@@ -37,8 +37,9 @@
 
 #define KERN_IMAGE_START                0x010000UL
 #define LINUX_MAGIC_ADDR                0x010008UL
+#define KERN_PARM_AREA_SIZE_ADDR        0x010430UL
 #define KERN_PARM_AREA                  0x010480UL
-#define KERN_PARM_AREA_SIZE             0x000380UL
+#define LEGACY_KERN_PARM_AREA_SIZE      0x000380UL
 #define INITRD_START                    0x800000UL
 #define INITRD_PARM_START               0x010408UL
 #define PARMFILE_START                  0x001000UL
@@ -110,6 +111,21 @@ static uint64_t bios_translate_addr(void *opaque, uint64_t srcaddr)
     return srcaddr + dstaddr;
 }
 
+static uint64_t get_max_kernel_cmdline_size(void)
+{
+    uint64_t *size_ptr = rom_ptr(KERN_PARM_AREA_SIZE_ADDR, sizeof(*size_ptr));
+
+    if (size_ptr) {
+        uint64_t size;
+
+        size = be64_to_cpu(*size_ptr);
+        if (size) {
+            return size;
+        }
+    }
+    return LEGACY_KERN_PARM_AREA_SIZE;
+}
+
 static void s390_ipl_realize(DeviceState *dev, Error **errp)
 {
     MachineState *ms = MACHINE(qdev_get_machine());
@@ -197,10 +213,13 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
             ipl->start_addr = KERN_IMAGE_START;
             /* Overwrite parameters in the kernel image, which are "rom" */
             if (parm_area) {
-                if (cmdline_size > KERN_PARM_AREA_SIZE) {
+                uint64_t max_cmdline_size = get_max_kernel_cmdline_size();
+
+                if (cmdline_size > max_cmdline_size) {
                     error_setg(errp,
-                               "kernel command line exceeds maximum size: %zu > %lu",
-                               cmdline_size, KERN_PARM_AREA_SIZE);
+                               "kernel command line exceeds maximum size:"
+                               " %zu > %" PRIu64,
+                               cmdline_size, max_cmdline_size);
                     return;
                 }
 
-- 
2.27.0