[PATCH 5.15.y v2 00/11] Delay VERW + RFDS 5.15.y backport

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v2:
- This includes the backport of recently upstreamed mitigation of a CPU
  vulnerability Register File Data Sampling (RFDS) (CVE-2023-28746).
  This is because RFDS has a dependency on "Delay VERW" series, and it
  is convenient to merge them together.
- rebased to v5.15.151

v1: https://lore.kernel.org/r/20240304-delay-verw-backport-5-15-y-v1-0-fd02afc00fec@xxxxxxxxxxxxxxx

This is the backport of recently upstreamed series that moves VERW
execution to a later point in exit-to-user path. This is needed because
in some cases it may be possible for data accessed after VERW executions
may end into MDS affected CPU buffers. Moving VERW closer to ring
transition reduces the attack surface.

- The series includes a dependency commit f87bc8dc7a7c ("x86/asm: Add
  _ASM_RIP() macro for x86-64 (%rip) suffix").

- Patch 2 includes a change that adds runtime patching for jmp (instead
  of verw in original series) due to lack of rip-relative relocation
  support in kernels <v6.5.

- Fixed warning:
  arch/x86/entry/entry.o: warning: objtool: mds_verw_sel+0x0: unreachable instruction.

- Resolved merge conflicts in:
	swapgs_restore_regs_and_return_to_usermode in entry_64.S.
	__vmx_vcpu_run in vmenter.S.
	vmx_update_fb_clear_dis in vmx.c.

- Boot tested with KASLR and KPTI enabled.

- Verified VERW being executed with mitigation ON, and not being
  executed with mitigation turned OFF.

To: stable@xxxxxxxxxxxxxxx

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
---

---
H. Peter Anvin (Intel) (1):
      x86/asm: Add _ASM_RIP() macro for x86-64 (%rip) suffix

Pawan Gupta (9):
      x86/bugs: Add asm helpers for executing VERW
      x86/entry_64: Add VERW just before userspace transition
      x86/entry_32: Add VERW just before userspace transition
      x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key
      KVM/VMX: Move VERW closer to VMentry for MDS mitigation
      x86/mmio: Disable KVM mitigation when X86_FEATURE_CLEAR_CPU_BUF is set
      Documentation/hw-vuln: Add documentation for RFDS
      x86/rfds: Mitigate Register File Data Sampling (RFDS)
      KVM/x86: Export RFDS_NO and RFDS_CLEAR to guests

Sean Christopherson (1):
      KVM/VMX: Use BT+JNC, i.e. EFLAGS.CF to select VMRESUME vs. VMLAUNCH

 Documentation/ABI/testing/sysfs-devices-system-cpu |   1 +
 Documentation/admin-guide/hw-vuln/index.rst        |   1 +
 .../admin-guide/hw-vuln/reg-file-data-sampling.rst | 104 ++++++++++++++++++++
 Documentation/admin-guide/kernel-parameters.txt    |  21 ++++
 Documentation/x86/mds.rst                          |  38 +++++---
 arch/x86/Kconfig                                   |  11 +++
 arch/x86/entry/entry.S                             |  23 +++++
 arch/x86/entry/entry_32.S                          |   3 +
 arch/x86/entry/entry_64.S                          |  11 +++
 arch/x86/entry/entry_64_compat.S                   |   1 +
 arch/x86/include/asm/asm.h                         |   5 +
 arch/x86/include/asm/cpufeatures.h                 |   3 +-
 arch/x86/include/asm/entry-common.h                |   1 -
 arch/x86/include/asm/msr-index.h                   |   8 ++
 arch/x86/include/asm/nospec-branch.h               |  27 +++---
 arch/x86/kernel/cpu/bugs.c                         | 107 ++++++++++++++++++---
 arch/x86/kernel/cpu/common.c                       |  38 +++++++-
 arch/x86/kernel/nmi.c                              |   3 -
 arch/x86/kvm/vmx/run_flags.h                       |   7 +-
 arch/x86/kvm/vmx/vmenter.S                         |   9 +-
 arch/x86/kvm/vmx/vmx.c                             |  12 ++-
 arch/x86/kvm/x86.c                                 |   5 +-
 drivers/base/cpu.c                                 |   8 ++
 include/linux/cpu.h                                |   2 +
 24 files changed, 394 insertions(+), 55 deletions(-)
---
base-commit: 57436264850706f50887bbb2148ee2cc797c9485
change-id: 20240304-delay-verw-backport-5-15-y-e16f07fbb71e

Best regards,
-- 
Thanks,
Pawan






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