[PATCH 0/4] x86: cpuid: improve support for broken CPUID configurations

[Maxim Levitsky]

This patch series aims to harden the cpuid code against the case when
the hypervisor exposes a broken CPUID configuration to the guest,
in the form of having a feature disabled but not features that depend on it.

This is the more generic way to fix kernel panic in aes-ni kernel driver,
which was triggered by CPUID configuration in which AVX is disabled but
not AVX2.

https://lore.kernel.org/all/20211103145231.GA4485@xxxxxxxxxxxxxxxxxxx/T/

This was tested by booting a guest with AVX disabled and not AVX2,
and observing that both a warning is now printed in dmesg, and
that avx2 is gone from /proc/cpuinfo.

Best regards,
	Maxim Levitsky

Maxim Levitsky (4):
  perf/x86/intel/lbr: use setup_clear_cpu_cap instead of clear_cpu_cap
  x86/cpuid: refactor setup_clear_cpu_cap/clear_feature
  x86/cpuid: move filter_cpuid_features to cpuid-deps.c
  x86/cpuid: check for dependencies violations in CPUID and attempt to
    fix them

 arch/x86/events/intel/lbr.c       |  2 +-
 arch/x86/include/asm/cpufeature.h |  1 +
 arch/x86/kernel/cpu/common.c      | 50 +-----------------
 arch/x86/kernel/cpu/cpuid-deps.c  | 84 +++++++++++++++++++++++++++----
 4 files changed, 78 insertions(+), 59 deletions(-)

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2.26.3