On 24/06/2020 09.52, Janosch Frank wrote:
jump_to_low_kernel() and the functions that it calls will already or
64 bit addressing into the reset psw mask when executing
jump_to_IPL_2() after the diag308 subcode 1.
Hmm, the jump_to_IPL_code() also sets the 64-bit addressing bits ... but
jump_to_low_kernel() has some logic that tests for the bits before that
function is called:
/* Trying to get PSW at zero address */
if (*((uint64_t *)0) & RESET_PSW_MASK) {
jump_to_IPL_code((*((uint64_t *)0)) & 0x7fffffff);
}
Could it be that the code in dasd-ipl.c has been written with that
if-statement in mind?
Thomas
The kernel proper is then branched to rather than doing a full PSW
change.
Signed-off-by: Janosch Frank <fran...@linux.ibm.com>
---
pc-bios/s390-ccw/dasd-ipl.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/pc-bios/s390-ccw/dasd-ipl.c b/pc-bios/s390-ccw/dasd-ipl.c
index 0fc879bb8e..e8f2846740 100644
--- a/pc-bios/s390-ccw/dasd-ipl.c
+++ b/pc-bios/s390-ccw/dasd-ipl.c
@@ -206,7 +206,6 @@ static void run_ipl2(SubChannelId schid, uint16_t cutype,
uint32_t addr)
*/
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 */
@@ -229,7 +228,5 @@ void dasd_ipl(SubChannelId schid, uint16_t cutype)
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();
}
