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pc-bios: s390x: Add a comment to the io and external new PSW setup

Message ID 20200715140820.3401-1-frankja@linux.ibm.com
State New
Headers show
Series pc-bios: s390x: Add a comment to the io and external new PSW setup | expand

Commit Message

Janosch Frank July 15, 2020, 2:08 p.m. UTC 
Normally they don't need to be set up before waiting for an interrupt
but are set up on boot. The BIOS however might overwrite the lowcore
(and hence the PSWs) when loading a blob into memory and therefore
needs to set up those PSWs more often.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
---
 pc-bios/s390-ccw/start.S | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)
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Patch

diff --git a/pc-bios/s390-ccw/start.S b/pc-bios/s390-ccw/start.S
index 01c4c21b26..b0fcb918cc 100644
--- a/pc-bios/s390-ccw/start.S
+++ b/pc-bios/s390-ccw/start.S
@@ -64,7 +64,10 @@  consume_sclp_int:
         stctg   %c0,%c0,0(%r15)
         oi      6(%r15),0x2
         lctlg   %c0,%c0,0(%r15)
-        /* prepare external call handler */
+        /*
+         * Prepare external new PSW as it might have been overwritten
+         * by a loaded blob
+         */
         larl %r1, external_new_code
         stg %r1, 0x1b8
         larl %r1, external_new_mask
@@ -84,7 +87,10 @@  consume_io_int:
         stctg %c6,%c6,0(%r15)
         oi    4(%r15), 0xff
         lctlg %c6,%c6,0(%r15)
-        /* prepare i/o call handler */
+        /*
+         * Prepare i/o new PSW as it might have been overwritten
+         * by a loaded blob
+         */
         larl  %r1, io_new_code
         stg   %r1, 0x1f8
         larl  %r1, io_new_mask