Wenlong Hou from Ant group reported two problems during the FRED
initialization:
https://lore.kernel.org/lkml/cover.1718972598.git.houwenlong.hwl@antgroup.com/

The first problem is that spurious_interrupt() gets called on the
HYPERVISOR_CALLBACK_VECTOR vector.  Because kvm_guest_init(), being
executed way before trap_init() in which it is decided that whether
FRED will be enabled or not, calls sysvec_install() to install
HYPERVISOR_CALLBACK_VECTOR's interrupt handler into FRED system
vector dispatch table or IDT depending on whether FRED is enabled.

The other problem is that the #PF handler gets a wrong faulting
address from the stack instead of CR2 before FRED is enabled.
Because the #PF handler fetches its faulting addresss from the
stack or CR2 based on whether FRED is available rather than active.

This patchset fixes the 2 problems with suggestions from tglx:

  1) Parse cmdline param "fred=" in cpu_parse_early_param() to
     minimize the gap mentioned above, before kvm_guest_init().

  2) Enable FRED right after init_mem_mapping() to switch to FRED
     from early IDT ASAP, avoid intermediately using the IDT #PF
     handler.


Xin Li (Intel) (4):
  x86/fred: Parse cmdline param "fred=" in cpu_parse_early_param()
  x86/fred: Write to FRED MSRs with wrmsrns()
  x86/fred: Split FRED RSP initialization into a separate function
  x86/fred: Enable FRED right after init_mem_mapping()

 arch/x86/include/asm/fred.h  |  2 ++
 arch/x86/kernel/cpu/common.c |  9 ++++---
 arch/x86/kernel/fred.c       | 50 +++++++++++++++++++++---------------
 arch/x86/kernel/setup.c      |  7 ++++-
 arch/x86/kernel/smpboot.c    |  6 +++++
 arch/x86/kernel/traps.c      | 30 +++-------------------
 6 files changed, 54 insertions(+), 50 deletions(-)


base-commit: e70c87e103e2e3842bf4c55a66c83560a1387925
-- 
2.45.2