linux-kernel - Re: [PATCH v7 67/72] x86/smpboot: Load TSS and getcpu GDT entry before loading IDT

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Date:   Tue, 8 Sep 2020 20:42:34 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Joerg Roedel <joro@...tes.org>, x86@...nel.org, 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>,
        Tom Lendacky <thomas.lendacky@....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 v7 67/72] x86/smpboot: Load TSS and getcpu GDT entry
 before loading IDT

On Tue, Sep 08, 2020 at 07:20:42PM +0200, Borislav Petkov wrote:
> On Mon, Sep 07, 2020 at 03:16:08PM +0200, Joerg Roedel wrote:
> > +void cpu_init_exception_handling(void)
> > +{
> > +	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
> > +	int cpu = raw_smp_processor_id();
> > +
> > +	/* paranoid_entry() gets the CPU number from the GDT */
> > +	setup_getcpu(cpu);
> > +
> > +	/* IST vectors need TSS to be set up. */
> > +	tss_setup_ist(tss);
> > +	tss_setup_io_bitmap(tss);
> > +	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
> > +
> > +	load_TR_desc();
> 
> Aha, this is what you mean here in your 0th message. I'm guessing it is
> ok to do those things twice in start_secondary...

Yes, I think its best to do it twice, so that cpu_init() stays the CPU
state barrier it should be, independent of what happens before.


	Joerg