[Qemu-devel] BIOS, ACPI, CMOS and Windows EvenID: 4

[Gleb Natapov]

Hello,

 AML, that is shipped with BIOS, reads data from CMOS by directly
accessing ports 0x70-0x71. This makes windows guest unhappy. It logs
error EventID 4 into event log:

     ACPI BIOS is attempting to read from an illegal IO port address (0x71),
     which lies in the 0x70 - 0x71 protected address range. This could
     lead to system instability. Please contact your system vendor for
     technical assistance.

We ignored this error for a long time since there was no any stability
issues caused by it, but recently we encountered Windows 2008 reboot
problem (one of 10 reboots hangs with ACPI error) that, according to
Microsoft, is caused by CMOS access from AML code. Eliminating the
access indeed fixed reboot problem. ACPI spec defines a way to read
CMOS without accessing IO ports directly, but unfortunately neither
Windows XP nor Linux implements this part of the spec (it works in
Windows 2008 though). As far as I can see AML accesses CMOS in order
to see how much memory is present and configure PCI hole to be maximum
size. Is this really needed or we can just hard code a reasonably large
PCI hole like in patch below and eliminate CMOS access? Any other ideas
how to solve the problem?


Index: bios/acpi-dsdt.dsl
===================================================================
RCS file: /cvsroot/bochs/bochs/bios/acpi-dsdt.dsl,v
retrieving revision 1.3
diff -u -r1.3 acpi-dsdt.dsl
--- bios/acpi-dsdt.dsl  26 Jan 2008 09:15:27 -0000      1.3
+++ bios/acpi-dsdt.dsl  20 Aug 2008 12:54:04 -0000
@@ -27,20 +27,6 @@
 {
     Scope (\)
     {
-        /* CMOS memory access */
-        OperationRegion (CMS, SystemIO, 0x70, 0x02)
-        Field (CMS, ByteAcc, NoLock, Preserve)
-        {
-            CMSI,   8,
-            CMSD,   8
-        }
-        Method (CMRD, 1, NotSerialized)
-        {
-            Store (Arg0, CMSI)
-            Store (CMSD, Local0)
-            Return (Local0)
-        }
-
         /* Debug Output */
         OperationRegion (DBG, SystemIO, 0xb044, 0x04)
         Field (DBG, DWordAcc, NoLock, Preserve)
@@ -99,9 +85,7 @@
                 Package() {0x0005ffff, 3, LNKD, 0},
             })
 
-            Method (_CRS, 0, NotSerialized)
-            {
-            Name (MEMP, ResourceTemplate ()
+            Name (_CRS, ResourceTemplate ()
             {
                 WordBusNumber (ResourceProducer, MinFixed, MaxFixed, PosDecode,
                     0x0000,             // Address Space Granularity
@@ -139,25 +123,12 @@
                     ,, , AddressRangeMemory, TypeStatic)
                 DWordMemory (ResourceProducer, PosDecode, MinNotFixed, 
MaxFixed, NonCacheable, ReadWrite,
                     0x00000000,         // Address Space Granularity
-                    0x00000000,         // Address Range Minimum
+                    0xE0000000,         // Address Range Minimum
                     0xFEBFFFFF,         // Address Range Maximum
                     0x00000000,         // Address Translation Offset
-                    0x00000000,         // Address Length
-                    ,, MEMF, AddressRangeMemory, TypeStatic)
+                    0x1EC00000,         // Address Length
+                    ,, , AddressRangeMemory, TypeStatic)
             })
-                CreateDWordField (MEMP, \_SB.PCI0._CRS.MEMF._MIN, PMIN)
-                CreateDWordField (MEMP, \_SB.PCI0._CRS.MEMF._MAX, PMAX)
-                CreateDWordField (MEMP, \_SB.PCI0._CRS.MEMF._LEN, PLEN)
-                /* compute available RAM */
-                Add(CMRD(0x34), ShiftLeft(CMRD(0x35), 8), Local0)
-                ShiftLeft(Local0, 16, Local0)
-                Add(Local0, 0x1000000, Local0)
-                /* update field of last region */
-                Store(Local0, PMIN)
-                Subtract (PMAX, PMIN, PLEN)
-                Increment (PLEN)
-                Return (MEMP)
-            }
         }
     }
 
--
                        Gleb.