Re: [PATCH] x86/msr: do not warn on writes to OC_MAILBOX

From: Borislav Petkov
Date: Tue Sep 08 2020 - 14:02:42 EST

On Tue, Sep 08, 2020 at 07:42:12PM +0200, Jason A. Donenfeld wrote:
> Are you prepared to track down all the MSRs that might maybe do
> something naughty?

I'm not prepared - that's why this MSR filtering. To block *all* direct
MSR accesses from userspace in the future.

> Does `dd` warn when you run `dd if=/dev/zero of=/dev/sda`?

Yah, because that's the same as bricking your hardware. Geez.

> Probably not possible. Optimal values are related to the "silicon
> lottery" that occurs when you buy a new CPU. Different optimal values
> for different individual chips.

Let's wait for what Srinivas finds out. I'd let Intel decide what they
wanna do.