Re: [PATCH rdma-core] verbs: Do not copy uninitialized data in ibv_cmd_modify_qp

[Bart Van Assche <Bart.VanAssche-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org>]

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On Mon, 2017-01-02 at 14:14 -0700, Jason Gunthorpe wrote:
> I felt that passing uninitialized memory into the kernel was just
> in general a bad idea, and adding the branchs to copy zero instead of
> un-init is probably performance neutral.
> 
> Even so, I don't think we can fix valgrind, ioctl is a different case
> as ioctls are much more well defined, this is write() and valgrind
> would have to first know we are writing to a uverbs FD which seems
> challenging to determine, can valgrind already do this?

Hello Jason,

As far as I know there is not yet any code in Valgrind to interpret the
data sent from user space to kernel through the write() system call. Since
I do not know any application for which ibv_modify_qp() is in the hot path
I think modifying the ibv_modify_qp() implementation is fine.

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