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Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86 hardware_subarch

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On Wed, Feb 24, 2016 at 5:18 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
>
> On Feb 24, 2016 8:40 AM, "Andy Lutomirski" <luto@amacapital.net> wrote:
>>
>> On Feb 24, 2016 12:33 AM, "Ingo Molnar" <mingo@kernel.org> wrote:
>> >
>> > For hard coded platform quirks I'd suggest we add x86_platform.quirks
>> > flags. For
>> > example the F00F hack for Xen could be done via:
>> >
>> >         x86_platform.quirks.idt_remap = 0;
>> >
>>
>> Don't we unconditionally remap the IDT?  I think Kees did it for
>> general purpose hardening due to our complete inability to hide the
>> IDT address. I.e. I think we can remove the f00f condition entirely.
>>
>
> Kees can you confirm ?
>

No need.

        /*
         * Set the IDT descriptor to a fixed read-only location, so that the
         * "sidt" instruction will not leak the location of the kernel, and
         * to defend the IDT against arbitrary memory write vulnerabilities.
         * It will be reloaded in cpu_init() */
        __set_fixmap(FIX_RO_IDT, __pa_symbol(idt_table), PAGE_KERNEL_RO);
        idt_descr.address = fix_to_virt(FIX_RO_IDT);

IIUI this works around f00f as a side effect.  The only other thing
needed is the code that X86_BUG_F00F guards, which is responsible for
fixing up the error generated on attempted F00F exploitation from an
OOPS to a SIGILL.  I see no reason why that code couldn't be allowed
to run on even a PV guest on a F00F-affected CPU -- it would never
trigger anyway.

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[PATCH v3 00/11] x86/init: replace paravirt_enabled() were possible "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-02-23 08:30 +0100
  [PATCH v3 09/11] x86/boot: add BIT() to boot/bitops.h "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-02-23 08:30 +0100
  [PATCH v3 01/11] x86/boot: enumerate documentation for the x86 hardware_subarch "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-02-23 08:30 +0100
    Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86  hardware_subarch Ingo Molnar <mingo@kernel.org> - 2016-02-23 10:00 +0100
      Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86  hardware_subarch "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-02-23 11:40 +0100
        Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86  hardware_subarch "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-02-23 21:50 +0100
          Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86  hardware_subarch Ingo Molnar <mingo@kernel.org> - 2016-02-24 09:40 +0100
            Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86 hardware_subarch Andy Lutomirski <luto@amacapital.net> - 2016-02-24 17:50 +0100
              Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86 hardware_subarch Andy Lutomirski <luto@amacapital.net> - 2016-02-25 02:30 +0100
              Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86  hardware_subarch Ingo Molnar <mingo@kernel.org> - 2016-02-25 09:20 +0100
            Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86  hardware_subarch "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-03-02 01:50 +0100
              Re: [PATCH v3 01/11] x86/boot: enumerate documentation for the x86  hardware_subarch "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-03-02 20:50 +0100

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