We cannot specify a pin-GSI connection for the SCI directly in the _PRT
because that implies ActiveLow polarity, clashing with both qemu and the
MADT we prepare.
With this patch the RHEL-6 guest logs the following:
ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT]
ACPI: PCI Interrupt Link [LNKS] (IRQs *9)
ACPI: PCI Interrupt Link [LNKA] (IRQs 5 10 *11)
ACPI: PCI Interrupt Link [LNKB] (IRQs 5 10 *11)
ACPI: PCI Interrupt Link [LNKC] (IRQs 5 *10 11)
ACPI: PCI Interrupt Link [LNKD] (IRQs 5 *10 11)
The patch amends svn rev 13625. Testing it in a RHEL-6 guest, the problems
described in
<http://sourceforge.net/mailarchive/message.php?msg_id=29660862> do not
reappear.
The code is derived from Paolo Bonzini's patch (originally appearing as
SeaBIOS commit f64a472a, "acpi: reintroduce LNKS"). Said original patch is
copyrighted by Red Hat (our common employer), and it has been relicensed
<http://sourceforge.net/mailarchive/message.php?msg_id=30393854> to form
the basis of this derived patch for edk2. The latter is therefore
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <ler...@redhat.com>
---
OvmfPkg/AcpiTables/Dsdt.asl | 47 +++++++++++++++++++++++++++++++++++++++++-
1 files changed, 45 insertions(+), 2 deletions(-)
diff --git a/OvmfPkg/AcpiTables/Dsdt.asl b/OvmfPkg/AcpiTables/Dsdt.asl
index 12a4f14..6258dd9 100644
--- a/OvmfPkg/AcpiTables/Dsdt.asl
+++ b/OvmfPkg/AcpiTables/Dsdt.asl
@@ -203,10 +203,28 @@ DefinitionBlock ("Dsdt.aml", "DSDT", 1, "INTEL ", "OVMF
", 4) {
Package () {0x0000FFFF, 0x02, \_SB.PCI0.LPC.LNKB, 0x00},
Package () {0x0000FFFF, 0x03, \_SB.PCI0.LPC.LNKC, 0x00},
- Package () {0x0001FFFF, 0x00, 0x00, 0x09},
//
- // list of IRQs occupied thus far: 9
+ // Bus 0, Device 1, Pin 0 (INTA) is special; it corresponds to the
+ // internally generated SCI (System Control Interrupt), which is
+ // always routed to GSI 9. By setting the third (= Source) field to
+ // zero, we could use the fourth (= Source Index) field to hardwire
+ // the pin to GSI 9 directly.
+ //
+ // That way however, in accordance with the ACPI spec's description
+ // of SCI, the interrupt would be treated as "active low,
+ // shareable, level", and that doesn't match qemu.
//
+ // In QemuInstallAcpiMadtTable() [OvmfPkg/AcpiPlatformDxe/Qemu.c]
+ // we install an Interrupt Override Structure for the identity
+ // mapped IRQ#9 / GSI 9 (the corresponding bit being set in
+ // Pcd8259LegacyModeEdgeLevel), which describes the correct
+ // polarity (active high). As a consequence, some OS'en (eg. Linux)
+ // override the default (active low) polarity originating from the
+ // _PRT; others (eg. FreeBSD) don't. Therefore we need a separate
+ // link device just to specify a polarity that matches the MADT.
+ //
+ Package () {0x0001FFFF, 0x00, \_SB.PCI0.LPC.LNKS, 0x00},
+
Package () {0x0001FFFF, 0x01, \_SB.PCI0.LPC.LNKB, 0x00},
Package () {0x0001FFFF, 0x02, \_SB.PCI0.LPC.LNKC, 0x00},
Package () {0x0001FFFF, 0x03, \_SB.PCI0.LPC.LNKD, 0x00},
@@ -292,6 +310,31 @@ DefinitionBlock ("Dsdt.aml", "DSDT", 1, "INTEL ", "OVMF
", 4) {
Name (_ADR, 0x00010000)
//
+ // The SCI cannot be rerouted or disabled with PIRQRC[A:D]; we only
+ // need this link device in order to specify the polarity.
+ //
+ Device (LNKS) {
+ Name (_HID, EISAID("PNP0C0F"))
+ Name (_UID, 0)
+
+ Method (_STA, 0, NotSerialized) {
+ Return (0xB) // 0x1: device present
+ // 0x2: enabled and decoding resources
+ // 0x8: functioning properly
+ }
+ Method (_SRS, 1, NotSerialized) { /* no-op */ }
+ Method (_DIS, 0, NotSerialized) { /* no-op */ }
+
+ Name (_PRS, ResourceTemplate () {
+ Interrupt (ResourceConsumer, Level, ActiveHigh, Shared) { 9 }
+ //
+ // list of IRQs occupied thus far: 9
+ //
+ })
+ Method (_CRS, 0, NotSerialized) { Return (_PRS) }
+ }
+
+ //
// PCI Interrupt Routing Configuration Registers, PIRQRC[A:D]
//
OperationRegion (PRR0, PCI_Config, 0x60, 0x04)
--
1.7.1
------------------------------------------------------------------------------
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