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Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Paul Menzel <pmenzel@xxxxxxxxxxxxx>
- From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
- Date: Thu, 20 Apr 2023 13:17:40 +0200
- Cc: linux-kernel@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, David Woodhouse <dwmw2@xxxxxxxxxxxxx>, Brian Gerst <brgerst@xxxxxxxxx>, Arjan van de Veen <arjan@xxxxxxxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Paul McKenney <paulmck@xxxxxxxxxx>, Tom Lendacky <thomas.lendacky@xxxxxxx>, Sean Christopherson <seanjc@xxxxxxxxxx>, Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>, "Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxx>, Piotr Gorski <lucjan.lucjanov@xxxxxxxxx>, David Woodhouse <dwmw@xxxxxxxxxxxx>, Usama Arif <usama.arif@xxxxxxxxxxxxx>, Jürgen 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>
- Delivery-date: Thu, 20 Apr 2023 11:18:03 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Thu, Apr 20 2023 at 10:23, Andrew Cooper wrote:
> On 20/04/2023 9:32 am, Thomas Gleixner wrote:
>> I'm pondering to simply deny parallel mode if x2APIC is not there.
>
> I'm not sure if that will help much.
Spoilsport.
> Just because x2APIC is there doesn't mean it's in use. There are
> several generations of Intel system which have x2APIC but also use the
> opt-out bit in ACPI tables. There are some machines which have
> mismatched APIC-ness settings in the BIOS->OS handover.
>
> There's very little you can do on the BSP alone to know for certain that
> the APs come out of wait-for-SIPI already in x2APIC mode.
Yeah. Reading the APIC that early is going to be entertaining too :)
> One way is the ÆPIC Leak "locked into x2APIC mode" giant security
> bodge.
Bah.
> If the system really does have a CPU with an APIC ID above 0xfe, then
> chances are good that the APs come out consistently...
Anything else would be really magic :)
- References:
- [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
- Re: [patch 00/37] cpu/hotplug, x86: Reworked parallel CPU bringup
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