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    • Tom Lendacky's avatar
      x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h · c49a0a80
      Tom Lendacky authored
      There have been reports of RDRAND issues after resuming from suspend on
      some AMD family 15h and family 16h systems. This issue stems from a BIOS
      not performing the proper steps during resume to ensure RDRAND continues
      to function properly.
      RDRAND support is indicated by CPUID Fn00000001_ECX[30]. This bit can be
      reset by clearing MSR C001_1004[62]. Any software that checks for RDRAND
      support using CPUID, including the kernel, will believe that RDRAND is
      not supported.
      Update the CPU initialization to clear the RDRAND CPUID bit for any family
      15h and 16h processor that supports RDRAND. If it is known that the family
      15h or family 16h system does not have an RDRAND resume issue or that the
      system will not be placed in suspend, the "rdrand=force" kernel parameter
      can be used to stop the clearing of the RDRAND CPUID bit.
      Additionally, update the suspend and resume path to save and restore the
      MSR C001_1004 value to ensure that the RDRAND CPUID setting remains in
      place after resuming from suspend.
      Note, that clearing the RDRAND CPUID bit does not prevent a processor
      that normally supports the RDRAND instruction from executing it. So any
      code that determined the support based on family and model won't #UD.
      Signed-off-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
      Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
      Cc: Andrew Cooper <andrew.cooper3@citrix.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Chen Yu <yu.c.chen@intel.com>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Jonathan Corbet <corbet@lwn.net>
      Cc: Josh Poimboeuf <jpoimboe@redhat.com>
      Cc: Juergen Gross <jgross@suse.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>
      Cc: "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>
      Cc: Nathan Chancellor <natechancellor@gmail.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Pavel Machek <pavel@ucw.cz>
      Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
      Cc: <stable@vger.kernel.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: "x86@kernel.org" <x86@kernel.org>
      Link: https://lkml.kernel.org/r/7543af91666f491547bd86cebb1e17c66824ab9f.1566229943.git.thomas.lendacky@amd.com
  14. 15 Aug, 2019 3 commits
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  16. 09 Aug, 2019 5 commits