linux-kernel - [PATCH 0/4] x86: Restrict KVM-induced symbol exports to KVM

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Message-ID: <20251112173944.1380633-1-seanjc@google.com>
Date: Wed, 12 Nov 2025 09:39:40 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	Xin Li <xin@...or.com>, "H. Peter Anvin" <hpa@...or.com>, Peter Zijlstra <peterz@...radead.org>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Jarkko Sakkinen <jarkko@...nel.org>, 
	"Kirill A. Shutemov" <kas@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org, 
	kvm@...r.kernel.org, linux-sgx@...r.kernel.org, linux-coco@...ts.linux.dev, 
	Kai Huang <kai.huang@...el.com>
Subject: [PATCH 0/4] x86: Restrict KVM-induced symbol exports to KVM

Leverage and extend KVM's macro shenanigans to export symbols for KVM if
and only if kvm{,-amd,intel}.ko is being built as a module, and only for
the KVM modules that are being built.

Note, this approach isn't 100% precise, as exports that are only strictly
necessary for one of KVM's modules will get exported for all KVM modules.
But I don't see any value in being super precise as it's not like kvm.ko is
any more trustworthy tha kvm-{amd,intel}.ko (and it's easy to circumvent
"for module" exports by abusing module names (in out-of-tree code)).  And
maintaining precise exports would likely be a nightmare (as would writing
the macros to get the exports right).

Patches 1-3 drop superfluous exports that I found while digging around for
KVM-only exports.

Sean Christopherson (4):
  x86/bugs: Drop unnecessary export of "x86_spec_ctrl_base"
  x86/mtrr: Drop unnecessary export of "mtrr_state"
  x86/mm: Drop unnecessary export of "ptdump_walk_pgd_level_debugfs"
  x86: Restrict KVM-induced symbol exports to KVM modules where
    obvious/possible

 arch/x86/entry/entry.S             |  7 ++-
 arch/x86/entry/entry_64.S          |  3 +-
 arch/x86/entry/entry_64_fred.S     |  3 +-
 arch/x86/events/amd/core.c         |  5 ++-
 arch/x86/events/core.c             |  7 +--
 arch/x86/events/intel/lbr.c        |  3 +-
 arch/x86/events/intel/pt.c         |  7 +--
 arch/x86/include/asm/kvm_types.h   |  5 +++
 arch/x86/kernel/apic/apic.c        |  3 +-
 arch/x86/kernel/apic/apic_common.c |  3 +-
 arch/x86/kernel/cpu/amd.c          |  4 +-
 arch/x86/kernel/cpu/bugs.c         | 18 ++++----
 arch/x86/kernel/cpu/bus_lock.c     |  3 +-
 arch/x86/kernel/cpu/common.c       |  7 +--
 arch/x86/kernel/cpu/mtrr/generic.c |  1 -
 arch/x86/kernel/cpu/sgx/main.c     |  3 +-
 arch/x86/kernel/cpu/sgx/virt.c     |  5 ++-
 arch/x86/kernel/e820.c             |  3 +-
 arch/x86/kernel/fpu/core.c         | 21 ++++-----
 arch/x86/kernel/fpu/xstate.c       |  7 +--
 arch/x86/kernel/hw_breakpoint.c    |  3 +-
 arch/x86/kernel/irq.c              |  3 +-
 arch/x86/kernel/kvm.c              |  5 ++-
 arch/x86/kernel/nmi.c              |  5 +--
 arch/x86/kernel/process_64.c       |  5 +--
 arch/x86/kernel/reboot.c           |  5 ++-
 arch/x86/kernel/tsc.c              |  1 +
 arch/x86/lib/cache-smp.c           |  9 ++--
 arch/x86/lib/msr.c                 |  5 ++-
 arch/x86/mm/dump_pagetables.c      |  1 -
 arch/x86/mm/pat/memtype.c          |  3 +-
 arch/x86/mm/tlb.c                  |  5 ++-
 arch/x86/virt/vmx/tdx/tdx.c        | 69 +++++++++++++++---------------
 include/linux/kvm_types.h          | 14 ++++++
 34 files changed, 144 insertions(+), 107 deletions(-)


base-commit: 19e2126bba55df9de15d9100b922df1dad6d39a4
-- 
2.51.2.1041.gc1ab5b90ca-goog