Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 23 Jun 2020 18:13:45 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Andrew Cooper <andrew.cooper3@citrix.com>,
        Joerg Roedel <jroedel@suse.de>,
        Andy Lutomirski <luto@kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        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)
Message-ID: <20200623161345.GQ4817@hirez.programming.kicks-ass.net>
References: <20200623120433.GB14101@suse.de>
 <20200623125201.GG4817@hirez.programming.kicks-ass.net>
 <20200623134003.GD14101@suse.de>
 <20200623135916.GI4817@hirez.programming.kicks-ass.net>
 <20200623145344.GA117543@hirez.programming.kicks-ass.net>
 <20200623145914.GF14101@suse.de>
 <20200623152326.GL4817@hirez.programming.kicks-ass.net>
 <56af2f70-a1c6-aa64-006e-23f2f3880887@citrix.com>
 <20200623155204.GO4817@hirez.programming.kicks-ass.net>
 <dae40b7b-e584-1ab4-2ebe-13526cdec946@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <dae40b7b-e584-1ab4-2ebe-13526cdec946@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Jun 23, 2020 at 09:03:56AM -0700, Dave Hansen wrote:
> On 6/23/20 8:52 AM, Peter Zijlstra wrote:
> > Isn't current #MC unconditionally fatal from kernel? But yes, I was
> > sorta aware people want that changed.
> 
> Not unconditionally.  copy_to_iter_mcsafe() is a good example of one
> thing we _can_ handle.

Urgh, I thought that stuff was still pending.

Anyway, the important thing is that it is fatal if we hit early NMI.
Which I think still holds.