queue-5.10/x86-cpufeatures-add-cpuid_lnx_5-to-track-recently-added-linux-defined-word.patch

   1 From 8cb4a9a82b21623dbb4b3051dd30d98356cf95bc Mon Sep 17 00:00:00 2001
   2 From: Sean Christopherson <seanjc@google.com>
   3 Date: Thu, 4 Apr 2024 17:16:14 -0700
   4 Subject: x86/cpufeatures: Add CPUID_LNX_5 to track recently added Linux-defined word
   5
   6 From: Sean Christopherson <seanjc@google.com>
   7
   8 commit 8cb4a9a82b21623dbb4b3051dd30d98356cf95bc upstream.
   9
  10 Add CPUID_LNX_5 to track cpufeatures' word 21, and add the appropriate
  11 compile-time assert in KVM to prevent direct lookups on the features in
  12 CPUID_LNX_5.  KVM uses X86_FEATURE_* flags to manage guest CPUID, and so
  13 must translate features that are scattered by Linux from the Linux-defined
  14 bit to the hardware-defined bit, i.e. should never try to directly access
  15 scattered features in guest CPUID.
  16
  17 Opportunistically add NR_CPUID_WORDS to enum cpuid_leafs, along with a
  18 compile-time assert in KVM's CPUID infrastructure to ensure that future
  19 additions update cpuid_leafs along with NCAPINTS.
  20
  21 No functional change intended.
  22
  23 Fixes: 7f274e609f3d ("x86/cpufeatures: Add new word for scattered features")
  24 Cc: Sandipan Das <sandipan.das@amd.com>
  25 Signed-off-by: Sean Christopherson <seanjc@google.com>
  26 Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
  27 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  28 Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
  29 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  30 ---
  31  arch/x86/include/asm/cpufeature.h |    2 ++
  32  arch/x86/kvm/cpuid.h              |    2 ++
  33  2 files changed, 4 insertions(+)
  34
  35 --- a/arch/x86/include/asm/cpufeature.h
  36 +++ b/arch/x86/include/asm/cpufeature.h
  37 @@ -33,6 +33,8 @@ enum cpuid_leafs
  38         CPUID_7_EDX,
  39         CPUID_8000_001F_EAX,
  40         CPUID_8000_0021_EAX,
  41 +       CPUID_LNX_5,
  42 +       NR_CPUID_WORDS,
  43  };
  44
  45  #ifdef CONFIG_X86_FEATURE_NAMES
  46 --- a/arch/x86/kvm/cpuid.h
  47 +++ b/arch/x86/kvm/cpuid.h
  48 @@ -76,10 +76,12 @@ static const struct cpuid_reg reverse_cp
  49   */
  50  static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
  51  {
  52 +       BUILD_BUG_ON(NR_CPUID_WORDS != NCAPINTS);
  53         BUILD_BUG_ON(x86_leaf == CPUID_LNX_1);
  54         BUILD_BUG_ON(x86_leaf == CPUID_LNX_2);
  55         BUILD_BUG_ON(x86_leaf == CPUID_LNX_3);
  56         BUILD_BUG_ON(x86_leaf == CPUID_LNX_4);
  57 +       BUILD_BUG_ON(x86_leaf == CPUID_LNX_5);
  58         BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
  59         BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);
  60  }