On Mon, Jul 01, 2019 at 12:16:44PM +0200, Philippe Mathieu-Daudé wrote: > On 7/1/19 10:37 AM, Stefan Hajnoczi wrote: > > On Fri, Jun 28, 2019 at 02:45:29PM +0200, Damien Hedde wrote: > >> This series adds a python framework aiming to provide some ways to do fault > >> injection in a running vm. In its current state, it allows to easily > >> interact > >> with memory, change gpios and qom properties. > >> > >> The framework consists in a python script based on the qmp existing module > >> which allows to interact with the vm. > > > > How does this compare to qtest? There seems to be a lot of overlap > > between them. > > > > Why is it called "fault injection"? The commands seem to be > > general-purpose device testing functions (like qtest and libqos), not > > functions for testing error code paths as would be expected from a fault > > injection framework. > > I understand qtest is to test QEMU, while this framework/command is to > test how the guest react to an hardware faults.
The commands seems to be equivalent to qtest commands, just implemented as QMP commands. Damien: Can you explain the use case more and show some example test cases? > To use the qtest_mem commands you need to run QEMU with the qtest > chardev backend, while this series expose a QMP interface. > > To avoid the overlap, a cleaner follow up might be to have qtest wrap > these QMP commands (mostly like HMP commands do). > > Another note while looking at a glance, qtest uses the 1st cpu address > space view, this series allow to select a specific cpu. > > It makes sense to me to be able to select address spaces by name (more > generic, not restricted to a cpu view, since one might want to inject > fault in a device ram not always mapped to a cpu: dma, emac desc). The naming issue still stands: none of the commands actually perform fault injection. They can be used for other types of testing or even non-testing purposes. Fault injection commands would be "make the next watchdog expiry fail", "return error code X on the next DMA request", "report an AHCI link failure", etc. These commands are lower-level. Therefore, I think "fault injection framework" is a misnomer and will age poorly if this API is extended in the future. Stefan
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