linux-kernel - Re: [PATCH v6 69/76] x86/realmode: Setup AP jump table

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Date:   Tue, 1 Sep 2020 15:55:45 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>, hpa@...or.com,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Martin Radev <martin.b.radev@...il.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v6 69/76] x86/realmode: Setup AP jump table

On Mon, Aug 31, 2020 at 07:09:37PM +0200, Borislav Petkov wrote:
> On Mon, Aug 24, 2020 at 10:55:04AM +0200, Joerg Roedel wrote:
> > +	/* Check if AP Jump Table is non-zero and page-aligned */
> > +	if (!jump_table_addr || jump_table_addr & ~PAGE_MASK)
> > +		return 0;
> 
> I think you need to return !0 here so that the panic() below fires with
> a modified message:
> 
> 	panic("Failed to get/update SEV-ES AP Jump Table");
> 
> or are we gonna boot an UP guest still?

Right, this needs a !0 return value. This code runs once on the boot CPU
before the kernel starts the secondary CPUs, so a panic() is the right
thing to do if this fails.

Regards,

	Joerg