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Re: [patch] x86/smpboot: Disable parallel bootup if cc_vendor != NONE
- To: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
- From: Sean Christopherson <seanjc@xxxxxxxxxx>
- Date: Tue, 30 May 2023 09:56:34 -0700
- Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>, Tom Lendacky <thomas.lendacky@xxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, x86@xxxxxxxxxx, David Woodhouse <dwmw2@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Brian Gerst <brgerst@xxxxxxxxx>, Arjan van de Veen <arjan@xxxxxxxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Paul McKenney <paulmck@xxxxxxxxxx>, Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>, Paul Menzel <pmenzel@xxxxxxxxxxxxx>, "Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxx>, Piotr Gorski <lucjan.lucjanov@xxxxxxxxx>, Usama Arif <usama.arif@xxxxxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Russell King <linux@xxxxxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, Catalin Marinas <catalin.marinas@xxxxxxx>, Will Deacon <will@xxxxxxxxxx>, Guo Ren <guoren@xxxxxxxxxx>, linux-csky@xxxxxxxxxxxxxxx, Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>, linux-mips@xxxxxxxxxxxxxxx, "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>, Helge Deller <deller@xxxxxx>, linux-parisc@xxxxxxxxxxxxxxx, Paul Walmsley <paul.walmsley@xxxxxxxxxx>, Palmer Dabbelt <palmer@xxxxxxxxxxx>, linux-riscv@xxxxxxxxxxxxxxxxxxx, Mark Rutland <mark.rutland@xxxxxxx>, Sabin Rapan <sabrapan@xxxxxxxxxx>, "Michael Kelley (LINUX)" <mikelley@xxxxxxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
- Delivery-date: Tue, 30 May 2023 16:57:03 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Tue, May 30, 2023, Thomas Gleixner wrote:
> On Tue, May 30 2023 at 15:29, Kirill A. Shutemov wrote:
> > On Tue, May 30, 2023 at 02:09:17PM +0200, Thomas Gleixner wrote:
> >> The decision to allow parallel bringup of secondary CPUs checks
> >> CC_ATTR_GUEST_STATE_ENCRYPT to detect encrypted guests. Those cannot use
> >> parallel bootup because accessing the local APIC is intercepted and raises
> >> a #VC or #VE, which cannot be handled at that point.
> >>
> >> The check works correctly, but only for AMD encrypted guests. TDX does not
> >> set that flag.
> >>
> >> Check for cc_vendor != CC_VENDOR_NONE instead. That might be overbroad, but
> >> definitely works for both AMD and Intel.
> >
> > It boots fine with TDX, but I think it is wrong. cc_get_vendor() will
> > report CC_VENDOR_AMD even on bare metal if SME is enabled. I don't think
> > we want it.
>
> Right. Did not think about that.
>
> But the same way is CC_ATTR_GUEST_MEM_ENCRYPT overbroad for AMD. Only
> SEV-ES traps RDMSR if I'm understandig that maze correctly.
Ya, regular SEV doesn't encrypt register state.
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