Re: [PATCH 2/3] x86/bus_lock: Add support for AMD

Ravi Bangoria
2024-05-07T03:58:14Z

On 06-May-24 9:54 PM, Jim Mattson wrote:
> On Sun, Apr 28, 2024 at 11:08 PM Ravi Bangoria <ravi.bangoria@amd.com> wrote:
>>
>> Upcoming AMD uarch will support Bus Lock Detect (called Bus Lock Trap
>> in AMD docs). Add support for the same in Linux. Bus Lock Detect is
>> enumerated with cpuid 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[1].
>>
>> [1]: 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
>
> Is there any chance of getting something similar to Intel's "VMM
> bus-lock detection," which causes a trap-style VM-exit on a bus lock
> event?

You are probably asking about "Bus Lock Threshold". Please see
"15.14.5 Bus Lock Threshold" in the same doc. fwiw, Bus Lock Threshold
is of fault style.

Thanks,
Ravi