From: Peter Zijlstra <peterz@infradead.org>
To: Like Xu <like.xu.linux@gmail.com>
Cc: Sean Christopherson <seanjc@google.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
"H. Peter Anvin" <hpa@zytor.com>,
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Stefano Stabellini <sstabellini@kernel.org>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
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xen-devel@lists.xenproject.org,
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Vincent Chen <deanbo422@gmail.com>,
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Borislav Petkov <bp@alien8.de>,
x86@kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
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Juergen Gross <jgross@suse.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Jason Baron <jbaron@akamai.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH 00/15] perf: KVM: Fix, optimize, and clean up callbacks
Date: Fri, 27 Aug 2021 09:44:52 +0200 [thread overview]
Message-ID: <YSiX9OPcrDsr3P4C@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <fd3dcd6c-b3d5-4453-93fb-b46d0595534e@gmail.com>
On Fri, Aug 27, 2021 at 02:52:25PM +0800, Like Xu wrote:
> + STATIC BRANCH/CALL friends.
>
> On 27/8/2021 8:57 am, Sean Christopherson wrote:
> > This started out as a small series[1] to fix a KVM bug related to Intel PT
> > interrupt handling and snowballed horribly.
> >
> > The main problem being addressed is that the perf_guest_cbs are shared by
> > all CPUs, can be nullified by KVM during module unload, and are not
> > protected against concurrent access from NMI context.
>
> Shouldn't this be a generic issue of the static_call() usage ?
>
> At the beginning, we set up the static entry assuming perf_guest_cbs != NULL:
>
> if (perf_guest_cbs && perf_guest_cbs->handle_intel_pt_intr) {
> static_call_update(x86_guest_handle_intel_pt_intr,
> perf_guest_cbs->handle_intel_pt_intr);
> }
>
> and then we unset the perf_guest_cbs and do the static function call like this:
>
> DECLARE_STATIC_CALL(x86_guest_handle_intel_pt_intr,
> *(perf_guest_cbs->handle_intel_pt_intr));
> static int handle_pmi_common(struct pt_regs *regs, u64 status)
> {
> ...
> if (!static_call(x86_guest_handle_intel_pt_intr)())
> intel_pt_interrupt();
> ...
> }
You just have to make sure all static_call() invocations that started
before unreg are finished before continuing with the unload.
synchronize_rcu() can help with that.
This is module unload 101. Nothing specific to static_call().
next prev parent reply other threads:[~2021-08-27 7:49 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-27 0:57 [PATCH 00/15] perf: KVM: Fix, optimize, and clean up callbacks Sean Christopherson
2021-08-27 0:57 ` [PATCH 01/15] KVM: x86: Register perf callbacks after calling vendor's hardware_setup() Sean Christopherson
2021-08-27 0:57 ` [PATCH 02/15] KVM: x86: Register Processor Trace interrupt hook iff PT enabled in guest Sean Christopherson
2021-08-27 0:57 ` [PATCH 03/15] perf: Stop pretending that perf can handle multiple guest callbacks Sean Christopherson
2021-08-27 0:57 ` [PATCH 04/15] perf: Force architectures to opt-in to " Sean Christopherson
2021-08-27 0:57 ` [PATCH 05/15] perf: Track guest callbacks on a per-CPU basis Sean Christopherson
2021-08-27 7:15 ` Peter Zijlstra
2021-08-27 14:49 ` Sean Christopherson
2021-08-27 14:56 ` Peter Zijlstra
2021-08-27 15:22 ` Sean Christopherson
2021-08-27 0:57 ` [PATCH 06/15] KVM: x86: Register perf callbacks only when actively handling interrupt Sean Christopherson
2021-08-27 7:21 ` Peter Zijlstra
2021-08-27 0:57 ` [PATCH 07/15] KVM: Use dedicated flag to track if KVM is handling an NMI from guest Sean Christopherson
2021-08-27 7:30 ` Peter Zijlstra
2021-08-27 14:58 ` Sean Christopherson
2021-08-27 0:57 ` [PATCH 08/15] KVM: x86: Drop current_vcpu in favor of kvm_running_vcpu Sean Christopherson
2021-08-27 0:57 ` [PATCH 09/15] KVM: arm64: Register/unregister perf callbacks at vcpu load/put Sean Christopherson
2021-08-27 0:57 ` [PATCH 10/15] KVM: Move x86's perf guest info callbacks to generic KVM Sean Christopherson
2021-08-27 0:57 ` [PATCH 11/15] KVM: x86: Move Intel Processor Trace interrupt handler to vmx.c Sean Christopherson
2021-08-27 7:34 ` Peter Zijlstra
2021-08-27 0:57 ` [PATCH 12/15] KVM: arm64: Convert to the generic perf callbacks Sean Christopherson
2021-08-27 0:57 ` [PATCH 13/15] KVM: arm64: Drop perf.c and fold its tiny bit of code into pmu.c Sean Christopherson
2021-08-27 0:57 ` [PATCH 14/15] perf: Disallow bulk unregistering of guest callbacks and do cleanup Sean Christopherson
2021-08-27 0:57 ` [PATCH 15/15] perf: KVM: Indicate "in guest" via NULL ->is_in_guest callback Sean Christopherson
2021-08-27 6:52 ` [PATCH 00/15] perf: KVM: Fix, optimize, and clean up callbacks Like Xu
2021-08-27 7:44 ` Peter Zijlstra [this message]
2021-08-27 8:01 ` Like Xu
2021-08-27 10:47 ` Peter Zijlstra
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