[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <d9f5a2d4-9c73-45c5-9de9-12a4d1d9ee99@oracle.com>
Date: Thu, 23 May 2024 20:27:34 +0200
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: Andrew Cooper <andrew.cooper3@...rix.com>,
Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
kvm@...r.kernel.org
Cc: alexandre.chartre@...cle.com, linux-kernel@...r.kernel.org,
daniel.sneddon@...ux.intel.com, pawan.kumar.gupta@...ux.intel.com,
tglx@...utronix.de, konrad.wilk@...cle.com, peterz@...radead.org,
gregkh@...uxfoundation.org, seanjc@...gle.com,
dave.hansen@...ux.intel.com, nik.borisov@...e.com, kpsingh@...nel.org,
longman@...hat.com, bp@...en8.de, pbonzini@...hat.com
Subject: Re: [PATCH] x86/bhi: BHI mitigation can trigger warning in #DB
handler
On 5/23/24 19:53, Andrew Cooper wrote:
> On 23/05/2024 6:03 pm, Alexandre Chartre wrote:
>>
>> On 5/23/24 17:36, Dave Hansen wrote:
>>> On 5/23/24 07:52, Alexandre Chartre wrote:
>>>>> Should we wrap up this gem and put it with the other entry selftests?
>>>>
>>>> It looks like tools/testing/selftests/x86/single_step_syscall.c tests
>>>> sysenter with TF set but it doesn't check if the kernel issues any
>>>> warning.
>>>
>>> Does it actually trip the warning though? I'm a bit surprised that
>>> nobody reported it if so.
>>
>> single_step_syscall does trigger the warning:
>>
>> $ ./single_step_syscall
>> [RUN] Set TF and check nop
>> [OK] Survived with TF set and 26 traps
>> [RUN] Set TF and check syscall-less opportunistic sysret
>> [OK] Survived with TF set and 30 traps
>> [RUN] Set TF and check a fast syscall
>> [OK] Survived with TF set and 40 traps
>> [RUN] Fast syscall with TF cleared
>> [OK] Nothing unexpected happened
>> [RUN] Set TF and check SYSENTER
>> Got SIGSEGV with RIP=ed7fe579, TF=256
>> [RUN] Fast syscall with TF cleared
>> [OK] Nothing unexpected happened
>
> :-/
>
> What about the exit code?
>
> I find the absence of a [FAIL] concerning...
>
$ ./single_step_syscall
[RUN] Set TF and check nop
[OK] Survived with TF set and 26 traps
[RUN] Set TF and check syscall-less opportunistic sysret
[OK] Survived with TF set and 30 traps
[RUN] Set TF and check a fast syscall
[OK] Survived with TF set and 40 traps
[RUN] Fast syscall with TF cleared
[OK] Nothing unexpected happened
[RUN] Set TF and check SYSENTER
Got SIGSEGV with RIP=bb44b579, TF=256
[RUN] Fast syscall with TF cleared
[OK] Nothing unexpected happened
$ echo $?
0
The program runs as expected (but it doesn't expect much than a SIGSEGV).
It triggers a warning from the kernel but it doesn't check if a warning
was produced.
alex.
Powered by blists - more mailing lists