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Date:   Tue, 23 Jun 2020 18:10:10 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Andrew Cooper <andrew.cooper3@citrix.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Joerg Roedel <jroedel@suse.de>,
        Andy Lutomirski <luto@kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Tom Lendacky <Thomas.Lendacky@amd.com>,
        Mike Stunes <mstunes@vmware.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Juergen Gross <JGross@suse.com>,
        Jiri Slaby <jslaby@suse.cz>, Kees Cook <keescook@chromium.org>,
        kvm list <kvm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Thomas Hellstrom <thellstrom@vmware.com>,
        Linux Virtualization <virtualization@lists.linux-foundation.org>,
        X86 ML <x86@kernel.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: Should SEV-ES #VC use IST? (Re: [PATCH] Allow RDTSC and RDTSCP
 from userspace)
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On Tue, Jun 23, 2020 at 04:32:22PM +0100, Andrew Cooper wrote:
> MSR_MCG_STATUS.MCIP, and yes - any #MC before that point will
> immediately Shutdown.  Any #MC between that point and IRET will clobber
> its IST stack and end up sad.

Well, at some point we should simply accept that we're living a little
on the edge. That is, until we get IRET with a mask of to-reenable
vectors which has #MC, NMI and whatever else vectors. It would be even
better if that mask were configurable.

-- 
Regards/Gruss,
    Boris.

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