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Thu, 23 May 2024 10:53:38 -0700 (PDT) Received: from [10.125.231.30] ([217.156.233.157]) by smtp.gmail.com with ESMTPSA id af79cd13be357-792bf2a11e8sm1497940085a.58.2024.05.23.10.53.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 May 2024 10:53:37 -0700 (PDT) Message-ID: <0fcbfcba-9fe2-414c-8424-347364fcbf35@citrix.com> Date: Thu, 23 May 2024 18:53:34 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/bhi: BHI mitigation can trigger warning in #DB handler To: Alexandre Chartre , Dave Hansen , 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> <1c69f62e-0dee-4caa-9cbe-f43d8efd597b@oracle.com> <93510641-9032-4612-9424-c048145e883e@intel.com> <5ed7d3c8-63c3-48f3-aaeb-a19514f4ef5e@oracle.com> Content-Language: en-GB From: Andrew Cooper Autocrypt: addr=andrew.cooper3@citrix.com; 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charset=UTF-8 Content-Transfer-Encoding: 8bit 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