[PATCH v1 0/4] Enable FRED earlier

Xin Li (Intel)
2024-07-03T08:55:10Z

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