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pc: acpi: fix pvpanic for buggy guests 

In the old times, we always had pvpanic in ACPI and a _STA method told
the guest not to use it.  Automatic generation dropped the _STA method
as the specification says that missing _STA means enabled and working.
Some guests (Linux) had buggy drivers and this change made them unable
to utilize pvpanic.

A Linux patch is posted as well, but I think it's worth to make pvpanic
useable on old guests at the price of three lines and few bytes of SSDT.

The old _STA method was
  Method (_STA, 0, NotSerialized) {
      Store (PEST, Local0)
      If (LEqual (Local0, Zero)) {
          Return (Zero) }
      Else {
          Return (0x0F) }}

Igor pointed out that we don't need to use a method to return a constant
and that 0xB (don't show in UI) is the common definition now.

Also, the device used to be PEVT.  (PEVT as in "panic event"?)

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Radim Krčmář 2015-05-29 21:57:32 +02:00 committed by Michael S. Tsirkin
parent 99fbeafee8
commit 2332333c97
1 changed files with 4 additions and 1 deletions
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5
hw/i386/acpi-build.c
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@ -733,7 +733,7 @@ build_ssdt(GArray *table_data, GArray *linker,
if (misc->pvpanic_port) {
scope = aml_scope("\\_SB.PCI0.ISA");
dev = aml_device("PEVR");
dev = aml_device("PEVT");
aml_append(dev, aml_name_decl("_HID", aml_string("QEMU0001")));
crs = aml_resource_template();
@ -748,6 +748,9 @@ build_ssdt(GArray *table_data, GArray *linker,
aml_append(field, aml_named_field("PEPT", 8));
aml_append(dev, field);
/* device present, functioning, decoding, not shown in UI */
aml_append(dev, aml_name_decl("_STA", aml_int(0xB)));
method = aml_method("RDPT", 0);
aml_append(method, aml_store(aml_name("PEPT"), aml_local(0)));
aml_append(method, aml_return(aml_local(0)));