Re: [Qemu-block] [PATCH v2 7/7] iotests: new file to suppress Valgrind errors

[Kevin Wolf]

Am 11.06.2019 um 20:02 hat Andrey Shinkevich geschrieben:
> The Valgrind tool reports about an uninitialised memory usage when the
> initialization is actually not needed. For example, the buffer 'buf'
> instantiated on a stack of the function guess_disk_lchs().

I would be careful with calling initialisation "not needed". It means
that the test case may not behave entirely determinstic because the
uninitialised memory can vary between runs.

In this specific case, I assume that guess_disk_lchs() is called for a
null block node, for which .bdrv_co_preadv by default returns without
actually writing to the buffer. Instead of ignoring the valgrind error,
we could instead pass read-zeroes=on to the null block driver to make
the test deterministic.

(Unfortunately, while adding the read-zeroes option, we didn't add it to
the QAPI schema, so it's not available yet in -blockdev. I'm going to
send a fix for that, but most of the problematic test cases probably
don't even use -blockdev.)

Kevin