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Re: [Xen-devel] [PATCH 1/3] x86/boot: Remove cached CPUID data from the trampoline


  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Thu, 21 Nov 2019 15:23:02 +0000
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  • Cc: Juergen Gross <jgross@xxxxxxxx>, Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
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On 19/11/2019 16:44, Jan Beulich wrote:
> On 19.11.2019 16:15, Andrew Cooper wrote:
>> On 13/11/2019 13:29, Jan Beulich wrote:
>>> On 13.11.2019 14:22, Andrew Cooper wrote:
>>>> I am not convinced the behaviour is worth changing, and I don't have
>>>> time for this scope creep.
>>> There's no scope creep here at all.
>> Yes - it really is scope creep.
>>
>> This patch does not change the behaviour of Xen in the case of poor
>> virtualisation of the bit.  Xen will still crash either way.
> So I have to apologize. What I didn't notice is
>
>       if (disable & MSR_IA32_MISC_ENABLE_XD_DISABLE) {
>               write_efer(read_efer() | EFER_NX);
>               printk(KERN_INFO
>                      "re-enabled NX (Execute Disable) protection\n");
>       }
>
> in early_init_intel(). I simply didn't expect we'd already have
> such a blind EFER write. I therefore agree now that this is a
> pre-existing bug that you don't make any worse.
>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Thankyou.  I'll get this series in now, along with some other straggling
4.13 content.

~Andrew

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