From: Peter Zijlstra <peterz@infradead.org>
To: Sean Christopherson <seanjc@google.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>,
Jinchao Wang <wangjinchao600@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H . Peter Anvin" <hpa@zytor.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Ian Rogers <irogers@google.com>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, linux-perf-users@vger.kernel.org,
x86@kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org
Subject: Re: [PATCH v17 02/13] perf/x86, KVM: Prevent host debug register leak into guest OS on NMI
Date: Thu, 24 Sep 2026 11:23:05 +0200 [thread overview]
Message-ID: <20260924092305.GL2009045@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <arPw-N3HF3ehNGTQ@google.com>
On Wed, Sep 23, 2026 at 08:32:08AM -0700, Sean Christopherson wrote:
> > > + return -EBUSY;
> > > +
> > > for (i = 0; i < HBP_NUM; i++) {
> > > struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
> > >
> >
> > Note how the other -EBUSY return is a WARN. Why is silently not doing
> > anything not a WARN in this case?
>
> Probably because the WARN would trigger anytime KGDB's NMI craziness happens to
> hit a vCPU, i.e. isn't a kernel bug.
Yeah, but using KGDB to install a watchpoint would then have
perf/ptrace/whatnot trip the "Can't find any breakpoint slot" case and
WARN, even though it isn't actually their fault either.
next prev parent reply other threads:[~2026-09-24 9:23 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-22 4:24 [PATCH v17 00/13] tracing: wprobe: x86: Add wprobe for watchpoint Masami Hiramatsu (Google)
2026-09-22 4:24 ` [PATCH v17 01/13] x86/mce: Fix hardware debug register corruption on task migration Masami Hiramatsu (Google)
2026-09-22 4:40 ` sashiko-bot
2026-09-23 0:27 ` Borislav Petkov
2026-09-23 8:46 ` Peter Zijlstra
2026-09-23 8:56 ` Masami Hiramatsu
2026-09-22 4:25 ` [PATCH v17 02/13] perf/x86, KVM: Prevent host debug register leak into guest OS on NMI Masami Hiramatsu (Google)
2026-09-22 4:40 ` sashiko-bot
2026-09-23 8:51 ` Peter Zijlstra
2026-09-23 14:33 ` Sean Christopherson
2026-09-24 1:31 ` Masami Hiramatsu
2026-09-24 9:18 ` Peter Zijlstra
2026-09-23 9:15 ` Peter Zijlstra
2026-09-23 15:32 ` Sean Christopherson
2026-09-24 0:56 ` Masami Hiramatsu
2026-09-24 9:23 ` Peter Zijlstra [this message]
2026-09-22 4:25 ` [PATCH v17 03/13] x86/hw_breakpoints: Make DR7 updates NMI safe Masami Hiramatsu (Google)
2026-09-22 4:40 ` sashiko-bot
2026-09-23 9:13 ` Peter Zijlstra
2026-09-24 12:56 ` Masami Hiramatsu
2026-09-22 4:25 ` [PATCH v17 04/13] x86/hw_breakpoints: Add arch_modify_local_hw_breakpoint_addr() API Masami Hiramatsu (Google)
2026-09-22 4:39 ` sashiko-bot
2026-09-22 4:25 ` [PATCH v17 05/13] HWBP: Add modify_local_hw_breakpoint_addr() API Masami Hiramatsu (Google)
2026-09-22 4:35 ` sashiko-bot
2026-09-22 4:25 ` [PATCH v17 06/13] tracing/wprobe: Add wprobe (watchpoint probe) trace event support Masami Hiramatsu (Google)
2026-09-22 4:41 ` sashiko-bot
2026-09-22 4:26 ` [PATCH v17 07/13] x86: hw_breakpoint: Add a kconfig to clarify when a breakpoint fires Masami Hiramatsu (Google)
2026-09-22 4:32 ` sashiko-bot
2026-09-22 4:26 ` [PATCH v17 08/13] selftests: tracing: Add a basic testcase for wprobe Masami Hiramatsu (Google)
2026-09-22 4:32 ` sashiko-bot
2026-09-22 4:26 ` [PATCH v17 09/13] selftests: tracing: Add syntax " Masami Hiramatsu (Google)
2026-09-22 4:34 ` sashiko-bot
2026-09-22 4:26 ` [PATCH v17 10/13] tracing/wprobe: Add set_wprobe and clear_wprobe event triggers Masami Hiramatsu (Google)
2026-09-22 4:43 ` sashiko-bot
2026-09-25 2:26 ` Masami Hiramatsu
2026-09-22 4:26 ` [PATCH v17 11/13] selftests: tracing: Add wprobe trigger testcases Masami Hiramatsu (Google)
2026-09-22 4:41 ` sashiko-bot
2026-09-25 3:28 ` Masami Hiramatsu
2026-09-22 4:27 ` [PATCH v17 12/13] tracing/wprobe: Support BTF typecast in fetchargs Masami Hiramatsu (Google)
2026-09-22 4:42 ` sashiko-bot
2026-09-22 4:27 ` [PATCH v17 13/13] tracing/wprobe: Support BTF struct offset resolution in set_wprobe trigger Masami Hiramatsu (Google)
2026-09-22 4:43 ` sashiko-bot
2026-09-25 3:00 ` Masami Hiramatsu
2026-09-25 3:42 ` Masami Hiramatsu
2026-09-28 10:07 ` [PATCH v17 00/13] tracing: wprobe: x86: Add wprobe for watchpoint Li Pengfei
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