Re: [PATCH 5/7] util: Add read_remainder() and read_all_buf()

On Tue, Jan 28, 2025 at 07:48:49AM +0100, Stefano Brivio wrote:

On Tue, 28 Jan 2025 11:59:28 +1100 David Gibson wrote:

...

On Tue, Jan 28, 2025 at 12:15:30AM +0100, Stefano Brivio wrote:

...

These are symmetric to write_remainder() and write_all_buf() and almost a copy and paste of them, with the most notable differences being reversed reads/writes and a couple of better-safe-than-sorry asserts to keep Coverity happy.

So, there's one thing that needs to be not quite symmetric for the read() version: we need to handle EOF. At present, I believe these will enter an infinite loop on EOF, which is not a graceful failure mode.

It doesn't happen in our current usage where we close the socket once we're done,

I don't see how what we do with the socket is relevant. Couldn't we hit this case if qemu unexpectedly closed the socket or died?

but sure, if we use it for something else, boom. Let me add a rc == 0 case (which gets EIO or EINVAL, I'm not sure yet).

Or feel free to re-post this if you have clearer ideas how to fix this up (but only if tested).

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson