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From 2f0454ccd0dd12429e8c204933cafe71a248d4eb Mon Sep 17 00:00:00 2001
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From: Thomas Huth <thuth@redhat.com>
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Date: Mon, 14 Oct 2019 10:06:30 +0100
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Subject: [PATCH 05/21] pc-bios/s390-ccw/net: Use diag308 to reset machine
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 before jumping to the OS
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RH-Author: Thomas Huth <thuth@redhat.com>
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Message-id: <20191014100645.22862-3-thuth@redhat.com>
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Patchwork-id: 91777
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O-Subject: [RHEL-8.2.0 qemu-kvm PATCH v2 02/17] pc-bios/s390-ccw/net: Use diag308 to reset machine before jumping to the OS
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Bugzilla: 1664376
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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RH-Acked-by: David Hildenbrand <david@redhat.com>
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RH-Acked-by: Jens Freimann <jfreimann@redhat.com>
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The netboot firmware so far simply jumped directly into the OS kernel
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after the download has been completed. This, however, bears the risk
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that the virtio-net device still might be active in the background and
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incoming packets are still placed into the buffers - which could destroy
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memory of the now-running Linux kernel in case it did not take over the
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device fast enough. Also the SCLP console is not put into a well-defined
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state here. We should hand over the system in a clean state when jumping
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into the kernel, so let's use the same mechanism as it's done in the
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main s390-ccw firmware and reset the machine with diag308 into a clean
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state before jumping into the OS kernel code. To be able to share the
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code with the main s390-ccw firmware, the related functions are now
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extracted from bootmap.c into a new file called jump2ipl.c.
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Since we now also set the boot device schid at address 184 for the network
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boot device, this patch also slightly changes the way how we detect the
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entry points for non-ELF binary images: The code now looks for the "S390EP"
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magic first and then jumps to 0x10000 in case it has been found. This is
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necessary for booting from network devices, since the normal kernel code
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(where the PSW at ddress 0 points to) tries to do a block load from the
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boot device. This of course fails for a virtio-net device and causes the
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kernel to abort with a panic-PSW silently.
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Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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(cherry picked from commit 9a848adf45d6732e62551decb3c0255173090767)
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 pc-bios/s390-ccw/Makefile    |  4 +-
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 pc-bios/s390-ccw/bootmap.c   | 63 +-----------------------------
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 pc-bios/s390-ccw/bootmap.h   |  4 --
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 pc-bios/s390-ccw/jump2ipl.c  | 91 ++++++++++++++++++++++++++++++++++++++++++++
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 pc-bios/s390-ccw/netboot.mak |  3 +-
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 pc-bios/s390-ccw/netmain.c   | 11 +++++-
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 pc-bios/s390-ccw/s390-ccw.h  |  4 ++
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 7 files changed, 111 insertions(+), 69 deletions(-)
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 create mode 100644 pc-bios/s390-ccw/jump2ipl.c
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diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
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index 1712c2d..439e3cc 100644
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--- a/pc-bios/s390-ccw/Makefile
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+++ b/pc-bios/s390-ccw/Makefile
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@@ -9,7 +9,9 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
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 .PHONY : all clean build-all
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-OBJECTS = start.o main.o bootmap.o sclp.o virtio.o virtio-scsi.o virtio-blkdev.o libc.o menu.o
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+OBJECTS = start.o main.o bootmap.o jump2ipl.o sclp.o menu.o \
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+	  virtio.o virtio-scsi.o virtio-blkdev.o libc.o
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+
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 QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS))
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 QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -msoft-float
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 QEMU_CFLAGS += -march=z900 -fPIE -fno-strict-aliasing
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diff --git a/pc-bios/s390-ccw/bootmap.c b/pc-bios/s390-ccw/bootmap.c
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index ffbf671..d13b7cb 100644
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--- a/pc-bios/s390-ccw/bootmap.c
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+++ b/pc-bios/s390-ccw/bootmap.c
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@@ -29,14 +29,6 @@
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 /* Scratch space */
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 static uint8_t sec[MAX_SECTOR_SIZE*4] __attribute__((__aligned__(PAGE_SIZE)));
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-typedef struct ResetInfo {
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-    uint32_t ipl_mask;
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-    uint32_t ipl_addr;
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-    uint32_t ipl_continue;
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-} ResetInfo;
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-
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-static ResetInfo save;
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-
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 const uint8_t el_torito_magic[] = "EL TORITO SPECIFICATION"
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                                   "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
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@@ -57,53 +49,6 @@ static inline bool is_iso_vd_valid(IsoVolDesc *vd)
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            vd->type <= VOL_DESC_TYPE_PARTITION;
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 }
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-static void jump_to_IPL_2(void)
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-{
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-    ResetInfo *current = 0;
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-
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-    void (*ipl)(void) = (void *) (uint64_t) current->ipl_continue;
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-    *current = save;
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-    ipl(); /* should not return */
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-}
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-
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-static void jump_to_IPL_code(uint64_t address)
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-{
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-    /* store the subsystem information _after_ the bootmap was loaded */
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-    write_subsystem_identification();
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-
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-    /* prevent unknown IPL types in the guest */
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-    if (iplb.pbt == S390_IPL_TYPE_QEMU_SCSI) {
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-        iplb.pbt = S390_IPL_TYPE_CCW;
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-        set_iplb(&iplb);
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-    }
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-
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-    /*
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-     * The IPL PSW is at address 0. We also must not overwrite the
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-     * content of non-BIOS memory after we loaded the guest, so we
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-     * save the original content and restore it in jump_to_IPL_2.
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-     */
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-    ResetInfo *current = 0;
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-
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-    save = *current;
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-    current->ipl_addr = (uint32_t) (uint64_t) &jump_to_IPL_2;
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-    current->ipl_continue = address & 0x7fffffff;
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-
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-    debug_print_int("set IPL addr to", current->ipl_continue);
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-
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-    /* Ensure the guest output starts fresh */
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-    sclp_print("\n");
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-
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-    /*
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-     * HACK ALERT.
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-     * We use the load normal reset to keep r15 unchanged. jump_to_IPL_2
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-     * can then use r15 as its stack pointer.
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-     */
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-    asm volatile("lghi 1,1\n\t"
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-                 "diag 1,1,0x308\n\t"
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-                 : : : "1", "memory");
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-    panic("\n! IPL returns !\n");
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-}
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-
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 /***********************************************************************
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  * IPL an ECKD DASD (CDL or LDL/CMS format)
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  */
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@@ -744,13 +689,7 @@ static void load_iso_bc_entry(IsoBcSection *load)
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                         (void *)((uint64_t)bswap16(s.load_segment)),
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                         blks_to_load);
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-    /* Trying to get PSW at zero address */
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-    if (*((uint64_t *)0) & IPL_PSW_MASK) {
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-        jump_to_IPL_code((*((uint64_t *)0)) & 0x7fffffff);
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-    }
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-
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-    /* Try default linux start address */
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-    jump_to_IPL_code(KERN_IMAGE_START);
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+    jump_to_low_kernel();
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 }
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 static uint32_t find_iso_bc(void)
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diff --git a/pc-bios/s390-ccw/bootmap.h b/pc-bios/s390-ccw/bootmap.h
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index f1ce423..94f53a5 100644
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--- a/pc-bios/s390-ccw/bootmap.h
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+++ b/pc-bios/s390-ccw/bootmap.h
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@@ -355,10 +355,6 @@ static inline uint32_t iso_733_to_u32(uint64_t x)
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 #define ISO_SECTOR_SIZE 2048
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 /* El Torito specifies boot image size in 512 byte blocks */
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 #define ET_SECTOR_SHIFT 2
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-#define KERN_IMAGE_START 0x010000UL
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-#define PSW_MASK_64 0x0000000100000000ULL
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-#define PSW_MASK_32 0x0000000080000000ULL
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-#define IPL_PSW_MASK (PSW_MASK_32 | PSW_MASK_64)
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 #define ISO_PRIMARY_VD_SECTOR 16
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diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c
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new file mode 100644
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index 0000000..266f150
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--- /dev/null
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+++ b/pc-bios/s390-ccw/jump2ipl.c
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@@ -0,0 +1,91 @@
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+/*
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+ * QEMU s390-ccw firmware - jump to IPL code
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+ *
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+ * This work is licensed under the terms of the GNU GPL, version 2 or (at
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+ * your option) any later version. See the COPYING file in the top-level
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+ * directory.
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+ */
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+
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+#include "libc.h"
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+#include "s390-ccw.h"
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+
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+#define KERN_IMAGE_START 0x010000UL
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+#define PSW_MASK_64 0x0000000100000000ULL
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+#define PSW_MASK_32 0x0000000080000000ULL
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+#define IPL_PSW_MASK (PSW_MASK_32 | PSW_MASK_64)
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+
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+typedef struct ResetInfo {
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+    uint32_t ipl_mask;
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+    uint32_t ipl_addr;
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+    uint32_t ipl_continue;
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+} ResetInfo;
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+
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+static ResetInfo save;
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+
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+static void jump_to_IPL_2(void)
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+{
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+    ResetInfo *current = 0;
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+
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+    void (*ipl)(void) = (void *) (uint64_t) current->ipl_continue;
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+    *current = save;
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+    ipl(); /* should not return */
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+}
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+
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+void jump_to_IPL_code(uint64_t address)
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+{
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+    /* store the subsystem information _after_ the bootmap was loaded */
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+    write_subsystem_identification();
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+
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+    /* prevent unknown IPL types in the guest */
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+    if (iplb.pbt == S390_IPL_TYPE_QEMU_SCSI) {
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+        iplb.pbt = S390_IPL_TYPE_CCW;
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+        set_iplb(&iplb);
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+    }
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+
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+    /*
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+     * The IPL PSW is at address 0. We also must not overwrite the
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+     * content of non-BIOS memory after we loaded the guest, so we
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+     * save the original content and restore it in jump_to_IPL_2.
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+     */
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+    ResetInfo *current = 0;
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+
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+    save = *current;
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+    current->ipl_addr = (uint32_t) (uint64_t) &jump_to_IPL_2;
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+    current->ipl_continue = address & 0x7fffffff;
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+
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+    debug_print_int("set IPL addr to", current->ipl_continue);
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+
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+    /* Ensure the guest output starts fresh */
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+    sclp_print("\n");
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+
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+    /*
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+     * HACK ALERT.
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+     * We use the load normal reset to keep r15 unchanged. jump_to_IPL_2
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+     * can then use r15 as its stack pointer.
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+     */
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+    asm volatile("lghi 1,1\n\t"
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+                 "diag 1,1,0x308\n\t"
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+                 : : : "1", "memory");
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+    panic("\n! IPL returns !\n");
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+}
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+
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+void jump_to_low_kernel(void)
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+{
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+    /*
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+     * If it looks like a Linux binary, i.e. there is the "S390EP" magic from
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+     * arch/s390/kernel/head.S here, then let's jump to the well-known Linux
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+     * kernel start address (when jumping to the PSW-at-zero address instead,
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+     * the kernel startup code fails when we booted from a network device).
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+     */
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+    if (!memcmp((char *)0x10008, "S390EP", 6)) {
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+        jump_to_IPL_code(KERN_IMAGE_START);
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+    }
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+
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+    /* Trying to get PSW at zero address */
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+    if (*((uint64_t *)0) & IPL_PSW_MASK) {
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+        jump_to_IPL_code((*((uint64_t *)0)) & 0x7fffffff);
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+    }
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+
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+    /* No other option left, so use the Linux kernel start address */
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+    jump_to_IPL_code(KERN_IMAGE_START);
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+}
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diff --git a/pc-bios/s390-ccw/netboot.mak b/pc-bios/s390-ccw/netboot.mak
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index a25d238..4f64128 100644
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--- a/pc-bios/s390-ccw/netboot.mak
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+++ b/pc-bios/s390-ccw/netboot.mak
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@@ -1,7 +1,8 @@
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 SLOF_DIR := $(SRC_PATH)/roms/SLOF
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-NETOBJS := start.o sclp.o virtio.o virtio-net.o netmain.o libnet.a libc.a
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+NETOBJS := start.o sclp.o virtio.o virtio-net.o jump2ipl.o netmain.o \
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+	   libnet.a libc.a
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 LIBC_INC := -nostdinc -I$(SLOF_DIR)/lib/libc/include
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 LIBNET_INC := -I$(SLOF_DIR)/lib/libnet
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diff --git a/pc-bios/s390-ccw/netmain.c b/pc-bios/s390-ccw/netmain.c
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index d86d46b..d60e84f 100644
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--- a/pc-bios/s390-ccw/netmain.c
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+++ b/pc-bios/s390-ccw/netmain.c
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@@ -281,6 +281,15 @@ void panic(const char *string)
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     }
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 }
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+void write_subsystem_identification(void)
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+{
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+    SubChannelId *schid = (SubChannelId *) 184;
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+    uint32_t *zeroes = (uint32_t *) 188;
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+
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+    *schid = net_schid;
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+    *zeroes = 0;
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+}
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+
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 static bool find_net_dev(Schib *schib, int dev_no)
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 {
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     int i, r;
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@@ -354,7 +363,7 @@ void main(void)
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     rc = net_load(NULL, (long)_start);
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     if (rc > 0) {
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         sclp_print("Network loading done, starting kernel...\n");
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-        asm volatile (" lpsw 0(%0) " : : "r"(0) : "memory");
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+        jump_to_low_kernel();
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     }
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     panic("Failed to load OS from network\n");
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diff --git a/pc-bios/s390-ccw/s390-ccw.h b/pc-bios/s390-ccw/s390-ccw.h
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index a1bdb4c..9828aa2 100644
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--- a/pc-bios/s390-ccw/s390-ccw.h
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+++ b/pc-bios/s390-ccw/s390-ccw.h
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@@ -87,6 +87,10 @@ ulong get_second(void);
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 /* bootmap.c */
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 void zipl_load(void);
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+/* jump2ipl.c */
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+void jump_to_IPL_code(uint64_t address);
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+void jump_to_low_kernel(void);
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+
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 /* menu.c */
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 void menu_set_parms(uint8_t boot_menu_flag, uint32_t boot_menu_timeout);
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 int menu_get_zipl_boot_index(const char *menu_data);
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-- 
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1.8.3.1
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