[PATCH 7/8] pvpanic : update pvpanic document

[Mihai Carabas]

From: Peng Hao <peng.hao2@zte.com.cn>

Add mmio support info in docs/specs/pvpanic.txt.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
---
 docs/specs/pvpanic.txt | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/docs/specs/pvpanic.txt b/docs/specs/pvpanic.txt
index a90fbca..b50140b 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 +9,9 @@ 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 SYSBUS device (using MMIO).
+
 ISA Interface
 -------------
 
@@ -24,6 +27,13 @@ bit 1: a guest panic has happened and will be handled by the 
guest;
        the host should record it or report it, but should not affect
        the execution of the guest.
 
+SYSBUS Interface
+----------------
+
+The SYSBUS interface is similar to the ISA interface except that it uses
+MMIO. For example, the arm virt machine could put the pvpanic device at
+[0x90b0000, 0x90b0001], where currently only the first byte is used.
+
 ACPI Interface
 --------------
 
-- 
1.8.3.1