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Date: Thu, 23 May 2024 18:53:34 +0100
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Subject: Re: [PATCH] x86/bhi: BHI mitigation can trigger warning in #DB
 handler
To: Alexandre Chartre <alexandre.chartre@oracle.com>,
 Dave Hansen <dave.hansen@intel.com>, x86@kernel.org, kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, daniel.sneddon@linux.intel.com,
 pawan.kumar.gupta@linux.intel.com, tglx@linutronix.de,
 konrad.wilk@oracle.com, peterz@infradead.org, gregkh@linuxfoundation.org,
 seanjc@google.com, dave.hansen@linux.intel.com, nik.borisov@suse.com,
 kpsingh@kernel.org, longman@redhat.com, bp@alien8.de, pbonzini@redhat.com
References: <20240523123322.3326690-1-alexandre.chartre@oracle.com>
 <a04d82be-a0d6-4e53-b47c-dba8402199e7@intel.com>
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From: Andrew Cooper <andrew.cooper3@citrix.com>
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In-Reply-To: <5ed7d3c8-63c3-48f3-aaeb-a19514f4ef5e@oracle.com>
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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...

~Andrew