pci-testdev: add optional memory bar

Add memory bar to pci-testdev.  Size is configurable using the membar
property.  Setting the size to zero (default) turns it off.  Can be used
to check whether guests handle large pci bars correctly.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/docs/specs/pci-testdev.txt b/docs/specs/pci-testdev.txt
index 128ae222ef..4280a1e73c 100644
--- a/docs/specs/pci-testdev.txt
+++ b/docs/specs/pci-testdev.txt
@@ -1,11 +1,11 @@
 pci-test is a device used for testing low level IO
 
-device implements up to two BARs: BAR0 and BAR1.
-Each BAR can be memory or IO. Guests must detect
-BAR type and act accordingly.
+device implements up to three BARs: BAR0, BAR1 and BAR2.
+Each of BAR 0+1 can be memory or IO. Guests must detect
+BAR types and act accordingly.
 
-Each BAR size is up to 4K bytes.
-Each BAR starts with the following header:
+BAR 0+1 size is up to 4K bytes each.
+BAR 0+1 starts with the following header:
 
 typedef struct PCITestDevHdr {
     uint8_t test;  <- write-only, starts a given test number
@@ -24,3 +24,8 @@ All registers are little endian.
 device is expected to always implement tests 0 to N on each BAR, and to add new
 tests with higher numbers.  In this way a guest can scan test numbers until it
 detects an access type that it does not support on this BAR, then stop.
+
+BAR2 is a 64bit memory bar, without backing storage.  It is disabled
+by default and can be enabled using the membar=<size> property.  This
+can be used to test whether guests handle pci bars of a specific
+(possibly quite large) size correctly.