[PATCH v8 0/4] Prevent attempting updates known to fail

[Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>]

Now that XENLOG_INFO is the default logging level...

v8:
  * Fixed last bits mentioned by Jan in v7/patch1 (v8/patch2)
  * Rolled back to having new printk as INFO
  * Added v8/patch1 to ensure the existing early exit from
    early_cpu_init() has INFO severity as well.

Original cover letter:

Under certain conditions a CPU may not be able to perform microcode updates
even if hardware exists to that effect. In particular:

 * If Xen runs under certain hypervisors they won't allow microcode
   updates, and will signal this fact by reporting a microcode revision of
   -1.
 * If the DIS_MCU_LOAD bit is set, which is expected in some baremetal
   clouds where the owner may not trust the tenant, then the CPU is not
   capable of loading new microcode.

This series adds logic so that in both of these cases we don't needlessly
attempt updates that are not going to succeed. Patch summary:

Patch 1 Modifies the severity of the printk statement in
        early_microcode_init() to be INFO

Patch 2 Ignores microcode facilities when the current microcode revision is -1
        (was v7/patch1)

Patch 3 Moves the MSR_ARCH_CAPS read in tsx_init() to early_cpu_init() and
        early_microcode_init()
        (was v7/patch2)

Patch 4 Adds the logic to detect microcode updates being disabled on Intel.
        (was v7/patch3)

Alejandro Vallejo (4):
  x86/microcode: WARN->INFO for the "no ucode loading" log message
  x86/microcode: Ignore microcode loading interface for revision = -1
  x86: Read MSR_ARCH_CAPS immediately after early_microcode_init()
  x86/microcode: Disable microcode update handler if DIS_MCU_UPDATE is
    set

 xen/arch/x86/cpu/common.c             | 20 ++++++++++----
 xen/arch/x86/cpu/microcode/core.c     | 40 +++++++++++++++++++++++----
 xen/arch/x86/cpu/microcode/intel.c    | 13 +++++++++
 xen/arch/x86/cpu/microcode/private.h  |  7 +++++
 xen/arch/x86/include/asm/cpufeature.h |  1 +
 xen/arch/x86/include/asm/msr-index.h  |  5 ++++
 xen/arch/x86/include/asm/setup.h      |  2 +-
 xen/arch/x86/setup.c                  |  2 +-
 xen/arch/x86/tsx.c                    | 16 +++--------
 9 files changed, 82 insertions(+), 24 deletions(-)

-- 
2.34.1