[Qemu-arm] [PATCH] pvpanic : update pvpanic document

[Peng Hao]

Add mmio mode as a pci device support info in docs/specs/pvpanic.txt.

Signed-off-by: Peng Hao <address@hidden>
---
 docs/specs/pvpanic.txt | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/docs/specs/pvpanic.txt b/docs/specs/pvpanic.txt
index c7bbacc..6d62d72 100644
--- a/docs/specs/pvpanic.txt
+++ b/docs/specs/pvpanic.txt
@@ -1,7 +1,7 @@
 PVPANIC DEVICE
 ==============
 
-pvpanic device is a simulated ISA device, through which a guest panic
+pvpanic device is a simulated device, through which a guest panic
 event is sent to qemu, and a QMP event is generated. This allows
 management apps (e.g. libvirt) to be notified and respond to the event.
 
@@ -9,6 +9,10 @@ The management app has the option of waiting for 
GUEST_PANICKED events,
 and/or polling for guest-panicked RunState, to learn when the pvpanic
 device has fired a panic event.
 
+The pvpanic device can be implemented as an ISA device (using IOPORT),
+or, since qemu 4.0, as a PCI device (using MMIO address space of pci
+device).
+
 ISA Interface
 -------------
 
@@ -19,6 +23,13 @@ Software should set only bits both itself and the device 
recognize.
 Currently, only bit 0 is recognized, setting it indicates a guest panic
 has happened.
 
+PCI Interface
+-------------
+
+The PCI interface is similar to the ISA interface except that it uses
+MMIO. For example, the arm virt machine could enable pvpanic-pci device 
+according to adding "-device pvpanic-pci" in qemu command.
+
 ACPI Interface
 --------------
 
-- 
1.8.3.1