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Date: Wed, 16 Jun 2021 21:01:30 +0200
From: Joerg Roedel <joro@8bytes.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, Joerg Roedel <jroedel@suse.de>, hpa@zytor.com,
	Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
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	Dan Williams <dan.j.williams@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Juergen Gross <jgross@suse.com>, Kees Cook <keescook@chromium.org>,
	David Rientjes <rientjes@google.com>, Cfir Cohen <cfir@google.com>,
	Erdem Aktas <erdemaktas@google.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mike Stunes <mstunes@vmware.com>,
	Sean Christopherson <seanjc@google.com>,
	Martin Radev <martin.b.radev@gmail.com>,
	Arvind Sankar <nivedita@alum.mit.edu>, linux-coco@lists.linux.dev,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v5 3/6] x86/sev-es: Split up runtime #VC handler for
 correct state tracking
Message-ID: <YMpKim/3Dc41xvF7@8bytes.org>
References: <20210614135327.9921-1-joro@8bytes.org>
 <20210614135327.9921-4-joro@8bytes.org>
 <YMohCkW/mChNpkqi@hirez.programming.kicks-ass.net>
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In-Reply-To: <YMohCkW/mChNpkqi@hirez.programming.kicks-ass.net>

Hi Peter,

sorry, missed this email before sending out v6.

On Wed, Jun 16, 2021 at 06:04:26PM +0200, Peter Zijlstra wrote:
> On Mon, Jun 14, 2021 at 03:53:24PM +0200, Joerg Roedel wrote:
> >  _ASM_NOKPROBE(\asmsym)
> >  SYM_CODE_END(\asmsym)
> 
> Consistency with idtentry_mce_db would seem to suggest using \cfunc and
> noist_\cfunc.
> 
> amluto, tglx: do we have strong feelings on consistency?

Yeah, but this distinction does not make sense here, as none of the #VC
handlers C functions run on the actual #VC IST stack. The from-kernel
function might run on the fall-back stack (not really possible today
unless the hypervisor does something nasty). And the difference between
the fall-back stack and the actual IST stack is, that on the fall-back
stack nesting #VC exceptions is still supported.

> > +	vc_handle_trap_db(regs);
> 
> It's a bit sad this does user_mode(regs) again.

Okay, I will change this according your comments.

Thanks,

	Joerg