[Bug libc/27398] x86: Improve testing false positive for tst-cpu-features-cpuinfo with bad hardware.

["fweimer at redhat dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=27398

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |MOVED
             Status|REOPENED                    |RESOLVED

--- Comment #32 from Florian Weimer <fweimer at redhat dot com> ---
(In reply to Siddhesh Poyarekar from comment #3)
> It only reports failures on cpu0, on every run, none of the other cores:
> 
> $ taskset --cpu-list 0 ./testrun.sh elf/tst-cpu-features-cpuinfo | grep -B 3
> fail
> Checking HAS_CPU_FEATURE (HLE):
>   HAS_CPU_FEATURE (HLE): 1
>   cpuinfo (hle): 0
>  *** failure ***
> --
> Checking HAS_CPU_FEATURE (RTM):
>   HAS_CPU_FEATURE (RTM): 1
>   cpuinfo (rtm): 0
>  *** failure ***

This was fixed as a kernel bug:

commit e2a1256b17b16f9b9adf1b6fea56819e7b68e463
Author: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Date:   Mon Apr 4 17:35:45 2022 -0700

    x86/speculation: Restore speculation related MSRs during S3 resume

    After resuming from suspend-to-RAM, the MSRs that control CPU's
    speculative execution behavior are not being restored on the boot CPU.

    These MSRs are used to mitigate speculative execution vulnerabilities.
    Not restoring them correctly may leave the CPU vulnerable.  Secondary
    CPU's MSRs are correctly being restored at S3 resume by
    identify_secondary_cpu().

    During S3 resume, restore these MSRs for boot CPU when restoring its
    processor state.

    Fixes: 772439717dbf ("x86/bugs/intel: Set proper CPU features and setup
RDS")
    Reported-by: Neelima Krishnan <neelima.krishnan@intel.com>
    Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
    Tested-by: Neelima Krishnan <neelima.krishnan@intel.com>
    Acked-by: Borislav Petkov <bp@suse.de>
    Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Leaving this bug here at security- because it's not a glibc bug (disabling RTM
for glibc's own use does not mitigate the vulnerability).

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