From: sashiko-bot@kernel.org
To: "Adrian Hunter" <adrian.hunter@intel.com>
Cc: linux-perf-users@vger.kernel.org
Subject: Re: [PATCH 2/6] perf/x86/intel/pt: Stop tracing if VMXON has not yet happened
Date: Mon, 02 Nov 2026 07:59:03 +0000 [thread overview]
Message-ID: <sashiko-outbox-193065@kernel.org> (raw)
In-Reply-To: <20261102074039.26983-3-adrian.hunter@intel.com>
> On Broadwell, which does not support Intel PT in VMX operation
> (IA32_VMX_MISC[14] = 0), VMXON clears IA32_RTIT_CTL.TraceEn and any
> subsequent write to IA32_RTIT_CTL causes #GP.
>
> To avoid that, intel_pt_handle_vmx() sets pt->vmx_on so that
> pt_config_start() and pt_config_stop() skip writes to
> IA32_RTIT_CTL while VMX is active.
>
> However, pt->vmx_on is set before VMXON executes. An NMI in the window
> between setting pt->vmx_on and executing VMXON can then observe
> vmx_on == true while tracing is still enabled.
>
> In that case pt_config_stop() skips the write that would clear TraceEn,
> leaving tracing active. This can subsequently cause:
>
> [ ... ]
> kthread+0x2cb/0x3a0
> ret_from_fork+0x5ff/0x7f0
>
> Fixes: 1c5ac21a0e9b ("perf/x86/intel/pt: Don't die on VMXON")
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261102074039.26983-1-adrian.hunter@intel.com?part=2
next prev parent reply other threads:[~2026-11-02 7:59 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-02 7:40 [PATCH 0/6] perf/x86/intel/pt: Fix tracing across kexec, kdump and suspend Adrian Hunter
2026-11-02 7:40 ` [PATCH 1/6] irq_work: Re-raise pending irq_work after system resume Adrian Hunter
2026-11-02 7:51 ` sashiko-bot
2026-11-02 9:06 ` Peter Zijlstra
2026-11-02 10:54 ` Adrian Hunter
2026-11-02 7:40 ` [PATCH 2/6] perf/x86/intel/pt: Stop tracing if VMXON has not yet happened Adrian Hunter
2026-11-02 7:59 ` sashiko-bot [this message]
2026-11-02 9:57 ` Peter Zijlstra
2026-11-02 11:04 ` Adrian Hunter
2026-11-02 11:07 ` Peter Zijlstra
2026-11-02 7:40 ` [PATCH 3/6] perf/x86/intel/pt: Stop tracing at syscore shutdown Adrian Hunter
2026-11-02 8:05 ` sashiko-bot
2026-11-02 10:04 ` Peter Zijlstra
2026-11-02 10:23 ` Adrian Hunter
2026-11-02 11:01 ` Peter Zijlstra
2026-11-02 7:40 ` [PATCH 4/6] perf/x86/intel/pt: Clear TraceEn in hardware in cpu_emergency_stop_pt() Adrian Hunter
2026-11-02 8:21 ` sashiko-bot
2026-11-02 10:07 ` Peter Zijlstra
2026-11-02 7:40 ` [PATCH 5/6] perf/x86/intel/pt: Reset stale MSR state on CPU start and resume Adrian Hunter
2026-11-02 8:31 ` sashiko-bot
2026-11-02 7:40 ` [PATCH 6/6] perf/x86/intel/pt: Stop tracing across system suspend Adrian Hunter
2026-11-02 8:59 ` sashiko-bot
2026-11-02 10:10 ` [PATCH 0/6] perf/x86/intel/pt: Fix tracing across kexec, kdump and suspend Peter Zijlstra
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