I think you might be misunderstanding what the phrase "side channel attack" means. It's very difficult to protect against side-channel attacks, because of their very nature. There are a lot of ways someone can try to exploit a system and of course not all of them can be accounted for in advance. But not all side-channel attacks are practical, some are done for academic reasons and can only be done in controlled environments with contrived setup.

like check this out: https://www.tau.ac.il/~tromer/acoustic/

> Here, we describe a new acoustic cryptanalysis key extraction attack, applicable to GnuPG's current implementation of RSA. The attack can extract full 4096-bit RSA decryption keys from laptop computers (of various models), within an hour, using the sound generated by the computer during the decryption of some chosen ciphertexts.

So the seriousness of a side-channel attack is determined as a function of the impact of the exploit as well as how easy it is to carry out the exploit.

Meltdown in particular is nasty because it is relatively easy exploit and is undetectable and affects a ridiculously large range of hardware. So it is actually a pretty big deal. Yes there are side-channel attacks against Intel CPU's, but this isn't just any old side-channel attack.

I'm not misunderstanding anything. I'm simply of the opinion that secure multiuser systems aren't something we can do right now.

Here's just one of the more practical attacks http://palms.ee.princeton.edu/system/files/SP_vfinal.pdf

>but this isn't just any old side-channel attack.

It isn't, but you were already screwed. Now you're just slightly more screwed.

There’s a $250 billion cloud computing market that makes that assumption.

What about it? There's a huge market for cigarettes too.

And this is terrifying for me. I am giving away money so that people smarter than myself figure out how to secure my systems.