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Bug #7706

closed

cpuid_pass2 can clobber leaf 7

Added by Robert Mustacchi almost 7 years ago. Updated almost 7 years ago.

Status:
Closed
Priority:
Normal
Assignee:
Robert Mustacchi
Category:
kernel
Start date:
2016-12-29
Due date:
% Done:

100%

Estimated time:
Difficulty:
Medium
Tags:
Gerrit CR:
External Bug:

Description

When we started adding support for CPUID features in leaf 7, we neglected to notice a part of what happens in cpuid_pass2. Importantly, it will re-enumerate all of the standard leaves. Leaf 7 is different from other cpuid leaves, in that it uses %eax to index into it, but then also uses %ecx to suggest a sub leaf to look at.

However, with certain newer systems, we actually have a value in %ecx being enumerated. This means that when we come back around to re-enumerate it in cpuid_pass2, we end up referring to an invalid leaf, which causes us to end up zeroing the entire set. This causes us to end up removing all the features on this leaf.

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 #1

Updated by Electric Monk almost 7 years ago

  • Status changed from New to Closed

git commit b8692e0c2f0c23ce751c0af9c1efb4391bfd00f2

commit  b8692e0c2f0c23ce751c0af9c1efb4391bfd00f2
Author: Robert Mustacchi <rm@joyent.com>
Date:   2017-01-04T01:28:10.000Z

    7706 cpuid_pass2 can clobber leaf 7
    Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
    Reviewed by: Toomas Soome <tsoome@me.com>
    Approved by: Richard Lowe <richlowe@richlowe.net>

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