linux-kernel - Re: [PATCH v3 03/25] x86/sgx: Wipe out EREMOVE from sgx_free_epc

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Date:   Tue, 23 Mar 2021 17:32:58 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Kai Huang <kai.huang@...el.com>, kvm@...r.kernel.org,
        x86@...nel.org, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org, jarkko@...nel.org, luto@...nel.org,
        dave.hansen@...el.com, rick.p.edgecombe@...el.com,
        haitao.huang@...el.com, pbonzini@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com
Subject: Re: [PATCH v3 03/25] x86/sgx: Wipe out EREMOVE from
 sgx_free_epc_page()

On Tue, Mar 23, 2021 at 04:21:47PM +0000, Sean Christopherson wrote:
> I like the idea of pointing at the documentation.  The documentation should
> probably emphasize that something is very, very wrong.

Yap, because no matter how we formulate the error message, it still ain't enough
and needs a longer explanation.

> E.g. if a kernel bug triggers EREMOVE failure and isn't detected until
> the kernel is widely deployed in a fleet, then the folks deploying the
> kernel probably _should_ be in all out panic. For this variety of bug
> to escape that far, it means there are huge holes in test coverage, in
> both the kernel itself and in the infrasturcture of whoever is rolling
> out their new kernel.

You sound just like someone who works at a company with a big fleet, oh
wait...

:-)

And yap, you big fleeted guys will more likely catch it but we do have
all these other customers who have a handful of servers only so they
probably won't be able to do such a wide coverage.

So I hope they'll appreciate this longer explanation about what to do
when they hit it. And normally I wouldn't even care but we almost never
tell people to reboot their boxes to fix sh*t - that's the other OS.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette