linux-kernel - Re: [PATCH 3/4] mce/copyin: fix to not SIGBUS when copying from user hits poison

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Message-ID: <20210414131018.GG10709@zn.tnic>
Date:   Wed, 14 Apr 2021 15:10:18 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Jue Wang <juew@...gle.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, luto@...nel.org,
        naoya.horiguchi@....com, tony.luck@...el.com, x86@...nel.org,
        yaoaili@...gsoft.com
Subject: Re: [PATCH 3/4] mce/copyin: fix to not SIGBUS when copying from user
 hits poison

On Tue, Apr 13, 2021 at 10:47:21PM -0700, Jue Wang wrote:
> This path is when EPT #PF finds accesses to a hwpoisoned page and
> sends SIGBUS to user space (KVM exits into user space) with the same
> semantic as if regular #PF found access to a hwpoisoned page.
> 
> The KVM_X86_SET_MCE ioctl actually injects a machine check into the guest.
> 
> We are in process to launch a product with MCE recovery capability in
> a KVM based virtualization product and plan to expand the scope of the
> application of it in the near future.

Any pointers to code or is this all non-public? Any text on what that
product does with the MCEs?

> The in-memory database and analytical domain are definitely using it.
> A couple examples:
> SAP HANA - as we've tested and planned to launch as a strategic
> enterprise use case with MCE recovery capability in our product
> SQL server - https://support.microsoft.com/en-us/help/2967651/inf-sql-server-may-display-memory-corruption-and-recovery-errors

Aha, so they register callbacks for the processes to exec on a memory
error. Good to know, thanks for those.

Thx.

-- 
Regards/Gruss,
    Boris.

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