[PATCH 0/5] x86: uaccess CMPXCHG + KVM bug fixes

[Sean Christopherson <seanjc@google.com>]

Add uaccess macros for doing CMPXCHG on userspace addresses and use the
macros to fix KVM bugs by replacing flawed code that maps memory into the
kernel address space without proper mmu_notifier protection (or with
broken pfn calculations in one case).

Add yet another Kconfig for guarding asm_volatile_goto() to workaround a
clang-13 bug.  I've verified the test passes on gcc versions of arm64,
PPC, RISC-V, and s390x that also pass the CC_HAS_ASM_GOTO_OUTPUT test.

Patches 1-4 are tagged for stable@ as patches 3 and 4 (mostly 3) need a
backportable fix, and doing CMPXCHG on the userspace address is the
simplest fix from a KVM perspective.

Peter Zijlstra (1):
  x86/uaccess: Implement macros for CMPXCHG on user addresses

Sean Christopherson (4):
  Kconfig: Add option for asm goto w/ tied outputs to workaround
    clang-13 bug
  KVM: x86: Use __try_cmpxchg_user() to update guest PTE A/D bits
  KVM: x86: Use __try_cmpxchg_user() to emulate atomic accesses
  KVM: x86: Bail to userspace if emulation of atomic user access faults

 arch/x86/include/asm/uaccess.h | 131 +++++++++++++++++++++++++++++++++
 arch/x86/kvm/mmu/paging_tmpl.h |  45 +----------
 arch/x86/kvm/x86.c             |  35 ++++-----
 init/Kconfig                   |   4 +
 4 files changed, 150 insertions(+), 65 deletions(-)


base-commit: 26291c54e111ff6ba87a164d85d4a4e134b7315c
-- 
2.35.0.rc2.247.g8bbb082509-goog