apm_pm.asm

Timestamp:

Jul 10, 2023 1:46:21 PM (22 months ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

158203

Message:

BIOS: Added a way for the APM BIOS to halt the virtual CPU through port I/O instead of HLT to solve problems with obstinate guests (see bugref:6549).

File:

trunk/src/VBox/Devices/PC/BIOS/apm_pm.asm

-              r98103
+              r100456
 public          apm_pm16_entry
+;
+; This module is for protected mode only and therefore
+; 286+ only
+;
 SET_DEFAULT_CPU_286
 …
 apmf_idle:                              ; function 05h
+if 1
+                ; Port I/O based HLT equivalent using a custom BIOS I/O port.
+                ; Works in situations where HLT can't be used, such as Windows 3.1
+                ; in Standard mode or DR-DOS 5.0/6.0 EMM386.SYS.
+                push    si
+                push    cx
+                push    dx
+                mov     dx, 40Fh
+                mov     si, offset hlt_string
+                mov     cx,8
+                rep outsb
+                pop     dx
+                pop     cx
+                pop     si
+                jmp     apmw_success
+hlt_string      db      'Prochalt'
+else
+                ;
                 ; Windows 3.1 POWER.DRV in Standard mode calls into APM
 …
                 hlt
                 jmp     apmw_success
+endif
 apmf_busy:                              ; function 06h

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