pc-bios/s390-ccw: do a subsystem reset before running the guest
The loader BIOS has already activated several devices. Let's do a subsystem reset before jumping into the guest. As there is no direct way of doing so, we use diagnose 308 to bring the system in a defined state. This is similar to what kdump on s390 uses. We have to define a small trampoline function that restores the low bytes to whatever the bootmap has written there. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com> Reviewed-by: Alexander Graf <agraf@suse.de> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
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@ -58,6 +58,52 @@ struct mbr {
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/* Scratch space */
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static uint8_t sec[SECTOR_SIZE] __attribute__((__aligned__(SECTOR_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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ResetInfo save;
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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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void (*ipl)(void) = (void *) (uint64_t) current->ipl_continue;
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debug_print_addr("set IPL addr to", ipl);
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/* Ensure the guest output starts fresh */
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sclp_print("\n");
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*current = save;
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ipl(); /* should not return */
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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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/*
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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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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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* 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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virtio_panic("\n! IPL returns !\n");
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}
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/* Check for ZIPL magic. Returns 0 if not matched. */
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static int zipl_magic(uint8_t *ptr)
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{
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@ -123,7 +169,6 @@ static int zipl_run(struct scsi_blockptr *pte)
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{
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struct component_header *header;
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struct component_entry *entry;
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void (*ipl)(void);
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uint8_t tmp_sec[SECTOR_SIZE];
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virtio_read(pte->blockno, tmp_sec);
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@ -157,14 +202,8 @@ static int zipl_run(struct scsi_blockptr *pte)
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goto fail;
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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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/* And run the OS! */
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ipl = (void*)(entry->load_address & 0x7fffffff);
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debug_print_addr("set IPL addr to", ipl);
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/* should not return */
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ipl();
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jump_to_IPL_code(entry->load_address);
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return 0;
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