s390-bios: Support booting from real dasd device

Allows guest to boot from a vfio configured real dasd device.

Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <1554388475-18329-16-git-send-email-jjherne@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

pc-bios/s390-ccw/Makefile

@@ -10,7 +10,7 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
 .PHONY : all clean build-all
 
 OBJECTS = start.o main.o bootmap.o jump2ipl.o sclp.o menu.o \
-	  virtio.o virtio-scsi.o virtio-blkdev.o libc.o cio.o
+	  virtio.o virtio-scsi.o virtio-blkdev.o libc.o cio.o dasd-ipl.o
 
 QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS))
 QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -msoft-float

pc-bios/s390-ccw/dasd-ipl.c

@@ -0,0 +1,235 @@
+/*
+ * S390 IPL (boot) from a real DASD device via vfio framework.
+ *
+ * Copyright (c) 2019 Jason J. Herne <jjherne@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or (at
+ * your option) any later version. See the COPYING file in the top-level
+ * directory.
+ */
+
+#include "libc.h"
+#include "s390-ccw.h"
+#include "s390-arch.h"
+#include "dasd-ipl.h"
+#include "helper.h"
+
+static char prefix_page[PAGE_SIZE * 2]
+            __attribute__((__aligned__(PAGE_SIZE * 2)));
+
+static void enable_prefixing(void)
+{
+    memcpy(&prefix_page, lowcore, 4096);
+    set_prefix(ptr2u32(&prefix_page));
+}
+
+static void disable_prefixing(void)
+{
+    set_prefix(0);
+    /* Copy io interrupt info back to low core */
+    memcpy((void *)&lowcore->subchannel_id, prefix_page + 0xB8, 12);
+}
+
+static bool is_read_tic_ccw_chain(Ccw0 *ccw)
+{
+    Ccw0 *next_ccw = ccw + 1;
+
+    return ((ccw->cmd_code == CCW_CMD_DASD_READ ||
+            ccw->cmd_code == CCW_CMD_DASD_READ_MT) &&
+            ccw->chain && next_ccw->cmd_code == CCW_CMD_TIC);
+}
+
+static bool dynamic_cp_fixup(uint32_t ccw_addr, uint32_t  *next_cpa)
+{
+    Ccw0 *cur_ccw = (Ccw0 *)(uint64_t)ccw_addr;
+    Ccw0 *tic_ccw;
+
+    while (true) {
+        /* Skip over inline TIC (it might not have the chain bit on)  */
+        if (cur_ccw->cmd_code == CCW_CMD_TIC &&
+            cur_ccw->cda == ptr2u32(cur_ccw) - 8) {
+            cur_ccw += 1;
+            continue;
+        }
+
+        if (!cur_ccw->chain) {
+            break;
+        }
+        if (is_read_tic_ccw_chain(cur_ccw)) {
+            /*
+             * Breaking a chain of CCWs may alter the semantics or even the
+             * validity of a channel program. The heuristic implemented below
+             * seems to work well in practice for the channel programs
+             * generated by zipl.
+             */
+            tic_ccw = cur_ccw + 1;
+            *next_cpa = tic_ccw->cda;
+            cur_ccw->chain = 0;
+            return true;
+        }
+        cur_ccw += 1;
+    }
+    return false;
+}
+
+static int run_dynamic_ccw_program(SubChannelId schid, uint16_t cutype,
+                                   uint32_t cpa)
+{
+    bool has_next;
+    uint32_t next_cpa = 0;
+    int rc;
+
+    do {
+        has_next = dynamic_cp_fixup(cpa, &next_cpa);
+
+        print_int("executing ccw chain at ", cpa);
+        enable_prefixing();
+        rc = do_cio(schid, cutype, cpa, CCW_FMT0);
+        disable_prefixing();
+
+        if (rc) {
+            break;
+        }
+        cpa = next_cpa;
+    } while (has_next);
+
+    return rc;
+}
+
+static void make_readipl(void)
+{
+    Ccw0 *ccwIplRead = (Ccw0 *)0x00;
+
+    /* Create Read IPL ccw at address 0 */
+    ccwIplRead->cmd_code = CCW_CMD_READ_IPL;
+    ccwIplRead->cda = 0x00; /* Read into address 0x00 in main memory */
+    ccwIplRead->chain = 0; /* Chain flag */
+    ccwIplRead->count = 0x18; /* Read 0x18 bytes of data */
+}
+
+static void run_readipl(SubChannelId schid, uint16_t cutype)
+{
+    if (do_cio(schid, cutype, 0x00, CCW_FMT0)) {
+        panic("dasd-ipl: Failed to run Read IPL channel program\n");
+    }
+}
+
+/*
+ * The architecture states that IPL1 data should consist of a psw followed by
+ * format-0 READ and TIC CCWs. Let's sanity check.
+ */
+static void check_ipl1(void)
+{
+    Ccw0 *ccwread = (Ccw0 *)0x08;
+    Ccw0 *ccwtic = (Ccw0 *)0x10;
+
+    if (ccwread->cmd_code != CCW_CMD_DASD_READ ||
+        ccwtic->cmd_code != CCW_CMD_TIC) {
+        panic("dasd-ipl: IPL1 data invalid. Is this disk really bootable?\n");
+    }
+}
+
+static void check_ipl2(uint32_t ipl2_addr)
+{
+    Ccw0 *ccw = u32toptr(ipl2_addr);
+
+    if (ipl2_addr == 0x00) {
+        panic("IPL2 address invalid. Is this disk really bootable?\n");
+    }
+    if (ccw->cmd_code == 0x00) {
+        panic("IPL2 ccw data invalid. Is this disk really bootable?\n");
+    }
+}
+
+static uint32_t read_ipl2_addr(void)
+{
+    Ccw0 *ccwtic = (Ccw0 *)0x10;
+
+    return ccwtic->cda;
+}
+
+static void ipl1_fixup(void)
+{
+    Ccw0 *ccwSeek = (Ccw0 *) 0x08;
+    Ccw0 *ccwSearchID = (Ccw0 *) 0x10;
+    Ccw0 *ccwSearchTic = (Ccw0 *) 0x18;
+    Ccw0 *ccwRead = (Ccw0 *) 0x20;
+    CcwSeekData *seekData = (CcwSeekData *) 0x30;
+    CcwSearchIdData *searchData = (CcwSearchIdData *) 0x38;
+
+    /* move IPL1 CCWs to make room for CCWs needed to locate record 2 */
+    memcpy(ccwRead, (void *)0x08, 16);
+
+    /* Disable chaining so we don't TIC to IPL2 channel program */
+    ccwRead->chain = 0x00;
+
+    ccwSeek->cmd_code = CCW_CMD_DASD_SEEK;
+    ccwSeek->cda = ptr2u32(seekData);
+    ccwSeek->chain = 1;
+    ccwSeek->count = sizeof(*seekData);
+    seekData->reserved = 0x00;
+    seekData->cyl = 0x00;
+    seekData->head = 0x00;
+
+    ccwSearchID->cmd_code = CCW_CMD_DASD_SEARCH_ID_EQ;
+    ccwSearchID->cda = ptr2u32(searchData);
+    ccwSearchID->chain = 1;
+    ccwSearchID->count = sizeof(*searchData);
+    searchData->cyl = 0;
+    searchData->head = 0;
+    searchData->record = 2;
+
+    /* Go back to Search CCW if correct record not yet found */
+    ccwSearchTic->cmd_code = CCW_CMD_TIC;
+    ccwSearchTic->cda = ptr2u32(ccwSearchID);
+}
+
+static void run_ipl1(SubChannelId schid, uint16_t cutype)
+ {
+    uint32_t startAddr = 0x08;
+
+    if (do_cio(schid, cutype, startAddr, CCW_FMT0)) {
+        panic("dasd-ipl: Failed to run IPL1 channel program\n");
+    }
+}
+
+static void run_ipl2(SubChannelId schid, uint16_t cutype, uint32_t addr)
+{
+    if (run_dynamic_ccw_program(schid, cutype, addr)) {
+        panic("dasd-ipl: Failed to run IPL2 channel program\n");
+    }
+}
+
+/*
+ * Limitations in vfio-ccw support complicate the IPL process. Details can
+ * be found in docs/devel/s390-dasd-ipl.txt
+ */
+void dasd_ipl(SubChannelId schid, uint16_t cutype)
+{
+    PSWLegacy *pswl = (PSWLegacy *) 0x00;
+    uint32_t ipl2_addr;
+
+    /* Construct Read IPL CCW and run it to read IPL1 from boot disk */
+    make_readipl();
+    run_readipl(schid, cutype);
+    ipl2_addr = read_ipl2_addr();
+    check_ipl1();
+
+    /*
+     * Fixup IPL1 channel program to account for vfio-ccw limitations, then run
+     * it to read IPL2 channel program from boot disk.
+     */
+    ipl1_fixup();
+    run_ipl1(schid, cutype);
+    check_ipl2(ipl2_addr);
+
+    /*
+     * Run IPL2 channel program to read operating system code from boot disk
+     */
+    run_ipl2(schid, cutype, ipl2_addr);
+
+    /* Transfer control to the guest operating system */
+    pswl->mask |= PSW_MASK_EAMODE;   /* Force z-mode */
+    pswl->addr |= PSW_MASK_BAMODE;   /* ...          */
+    jump_to_low_kernel();
+}

pc-bios/s390-ccw/dasd-ipl.h

@@ -0,0 +1,16 @@
+/*
+ * S390 IPL (boot) from a real DASD device via vfio framework.
+ *
+ * Copyright (c) 2019 Jason J. Herne <jjherne@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or (at
+ * your option) any later version. See the COPYING file in the top-level
+ * directory.
+ */
+
+#ifndef DASD_IPL_H
+#define DASD_IPL_H
+
+void dasd_ipl(SubChannelId schid, uint16_t cutype);
+
+#endif /* DASD_IPL_H */

pc-bios/s390-ccw/main.c

@@ -13,6 +13,7 @@
 #include "s390-ccw.h"
 #include "cio.h"
 #include "virtio.h"
+#include "dasd-ipl.h"
 
 char stack[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
 static SubChannelId blk_schid = { .one = 1 };
@@ -209,6 +210,10 @@ int main(void)
 
     cutype = cu_type(blk_schid);
     switch (cutype) {
+    case CU_TYPE_DASD_3990:
+    case CU_TYPE_DASD_2107:
+        dasd_ipl(blk_schid, cutype); /* no return */
+        break;
     case CU_TYPE_VIRTIO:
         virtio_setup();
         zipl_load(); /* no return */

pc-bios/s390-ccw/s390-arch.h

@@ -87,4 +87,17 @@ typedef struct LowCore {
 
 extern LowCore const *lowcore;
 
+static inline void set_prefix(uint32_t address)
+{
+    asm volatile("spx %0" : : "m" (address) : "memory");
+}
+
+static inline uint32_t store_prefix(void)
+{
+    uint32_t address;
+
+    asm volatile("stpx %0" : "=m" (address));
+    return address;
+}
+
 #endif