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[v4,0/4] x86/cpu: Add Bus Lock Detect support for AMD

Message ID 20240808062937.1149-1-ravi.bangoria@amd.com (mailing list archive)
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Series x86/cpu: Add Bus Lock Detect support for AMD | expand

Message

Ravi Bangoria Aug. 8, 2024, 6:29 a.m. UTC 
Add Bus Lock Detect (called Bus Lock Trap in AMD docs) support for AMD
platforms. Bus Lock Detect is enumerated with CPUID Fn0000_0007_ECX_x0
bit [24 / BUSLOCKTRAP]. It can be enabled through MSR_IA32_DEBUGCTLMSR.
When enabled, hardware clears DR6[11] and raises a #DB exception on
occurrence of Bus Lock if CPL > 0. More detail about the feature can be
found in AMD APM:

  AMD64 Architecture Programmer's Manual Pub. 40332, Rev. 4.07 - June
  2023, Vol 2, 13.1.3.6 Bus Lock Trap
  https://bugzilla.kernel.org/attachment.cgi?id=304653

Patches are prepared on tip/master (532361ba3a0e).

v3: https://lore.kernel.org/r/20240806125442.1603-1-ravi.bangoria@amd.com
v3->v4:
 - Introduce CONFIG_X86_BUS_LOCK_DETECT, make it dependent on
   (CONFIG_CPU_SUP_INTEL || CONFIG_CPU_SUP_AMD). And make Bus Lock Detect
   feature dependent on CONFIG_X86_BUS_LOCK_DETECT.
 - Update documentation about Bus Lock Detect support on AMD.

Note:
A Qemu fix is also require to handle a corner case where a hardware
instruction or data breakpoint is created by Qemu remote debugger (gdb)
on the same instruction which also causes a Bus Lock. Qemu patch to
handle it can be found at:
https://lore.kernel.org/r/20240712095208.1553-1-ravi.bangoria@amd.com

Ravi Bangoria (4):
  x86/split_lock: Move Split and Bus lock code to a dedicated file
  x86/bus_lock: Add support for AMD
  KVM: SVM: Don't advertise Bus Lock Detect to guest if SVM support is
    missing
  KVM: SVM: Add Bus Lock Detect support

 Documentation/arch/x86/buslock.rst |   3 +-
 arch/x86/Kconfig                   |   8 +
 arch/x86/include/asm/cpu.h         |  11 +-
 arch/x86/kernel/cpu/Makefile       |   2 +
 arch/x86/kernel/cpu/bus_lock.c     | 406 ++++++++++++++++++++++++++++
 arch/x86/kernel/cpu/common.c       |   2 +
 arch/x86/kernel/cpu/intel.c        | 407 -----------------------------
 arch/x86/kvm/svm/nested.c          |   3 +-
 arch/x86/kvm/svm/svm.c             |  16 +-
 include/linux/sched.h              |   2 +-
 kernel/fork.c                      |   2 +-
 11 files changed, 448 insertions(+), 414 deletions(-)
 create mode 100644 arch/x86/kernel/cpu/bus_lock.c

Comments

Sean Christopherson Aug. 23, 2024, 11:47 p.m. UTC | #1 
On Thu, 08 Aug 2024 06:29:33 +0000, Ravi Bangoria wrote:
> Add Bus Lock Detect (called Bus Lock Trap in AMD docs) support for AMD
> platforms. Bus Lock Detect is enumerated with CPUID Fn0000_0007_ECX_x0
> bit [24 / BUSLOCKTRAP]. It can be enabled through MSR_IA32_DEBUGCTLMSR.
> When enabled, hardware clears DR6[11] and raises a #DB exception on
> occurrence of Bus Lock if CPL > 0. More detail about the feature can be
> found in AMD APM:
> 
> [...]

Applied patch 3 to kvm-x86 fixes, thanks!

[3/4] KVM: SVM: Don't advertise Bus Lock Detect to guest if SVM support is missing
      https://github.com/kvm-x86/linux/commit/54950bfe2b69

--
https://github.com/kvm-x86/linux/tree/next