diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/specs/pci-testdev.txt | 15 |
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. |