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@xxxxxxx 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@xxxxxxx 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 -- 2.34.1
