[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <YSiX9OPcrDsr3P4C@hirez.programming.kicks-ass.net>
Date: Fri, 27 Aug 2021 09:44:52 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Like Xu <like.xu.linux@...il.com>
Cc: Sean Christopherson <seanjc@...gle.com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
James Morse <james.morse@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
"H. Peter Anvin" <hpa@...or.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
Stefano Stabellini <sstabellini@...nel.org>,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
linux-csky@...r.kernel.org, linux-riscv@...ts.infradead.org,
kvm@...r.kernel.org, xen-devel@...ts.xenproject.org,
Artem Kashkanov <artem.kashkanov@...el.com>,
Zhu Lingshan <lingshan.zhu@...el.com>,
Will Deacon <will@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Marc Zyngier <maz@...nel.org>, Guo Ren <guoren@...nel.org>,
Nick Hu <nickhu@...estech.com>,
Greentime Hu <green.hu@...il.com>,
Vincent Chen <deanbo422@...il.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>, x86@...nel.org,
Paolo Bonzini <pbonzini@...hat.com>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Juergen Gross <jgross@...e.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Jason Baron <jbaron@...mai.com>,
Steven Rostedt <rostedt@...dmis.org>,
Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH 00/15] perf: KVM: Fix, optimize, and clean up callbacks
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().
Powered by blists - more mailing lists