From: Sean Christopherson <seanjc@google.com>
To: Like Xu <like.xu.linux@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Mark Rutland <mark.rutland@arm.com>, Jiri Olsa <jolsa@redhat.com>,
Namhyung Kim <namhyung@kernel.org>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, Artem Kashkanov <artem.kashkanov@intel.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 2/3] KVM: x86: Register Processor Trace interrupt hook iff PT enabled in guest
Date: Wed, 25 Aug 2021 20:09:34 +0000 [thread overview]
Message-ID: <YSajfuw7P2wacTGY@google.com> (raw)
In-Reply-To: <YSZa7dkw6t7yN6vL@google.com>
On Wed, Aug 25, 2021, Sean Christopherson wrote:
> On Wed, Aug 25, 2021, Like Xu wrote:
> > On 24/8/2021 3:37 am, Sean Christopherson wrote:
> > > @@ -11061,6 +11061,8 @@ int kvm_arch_hardware_setup(void *opaque)
> > > memcpy(&kvm_x86_ops, ops->runtime_ops, sizeof(kvm_x86_ops));
> > > kvm_ops_static_call_update();
> > > + if (ops->intel_pt_intr_in_guest && ops->intel_pt_intr_in_guest())
> > > + kvm_guest_cbs.handle_intel_pt_intr = kvm_handle_intel_pt_intr;
> >
> > Emm, it's still buggy.
> >
> > The guest "unknown NMI" from the host Intel PT can still be reproduced
> > after the following operation:
> >
> > rmmod kvm_intel
> > modprobe kvm-intel pt_mode=1 ept=1
> > rmmod kvm_intel
> > modprobe kvm-intel pt_mode=1 ept=0
> >
> > Since the handle_intel_pt_intr is not reset to NULL in kvm_arch_hardware_unsetup(),
> > and the previous function pointer still exists in the generic KVM data structure.
>
> Ooof, good catch. Any preference between nullifying handle_intel_pt_intr in
> setup() vs. unsetup()? I think I like the idea of "unwinding" during unsetup(),
> even though it splits the logic a bit.
Never mind, I figured out a way to clean all this up and land the PT interrupt
handler in vmx.c where it belongs. Getting there is a bit of a journey, but it's
very doable. That means unwinding in unsetup() is the preferred approach,
otherwise there would be potential for leaving a dangling pointer if a different
vendor module was succesfully loaded.
next prev parent reply other threads:[~2021-08-25 20:09 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-23 19:37 [PATCH 0/3] perf/x86/intel: KVM: PT intr handler fix and cleanup Sean Christopherson
2021-08-23 19:37 ` [PATCH 1/3] KVM: x86: Register perf callbacks after calling vendor's hardware_setup() Sean Christopherson
2021-08-23 19:37 ` [PATCH 2/3] KVM: x86: Register Processor Trace interrupt hook iff PT enabled in guest Sean Christopherson
2021-08-24 7:28 ` Alexander Shishkin
2021-08-24 14:11 ` Sean Christopherson
2021-08-25 7:24 ` Like Xu
2021-08-25 14:59 ` Sean Christopherson
2021-08-25 20:09 ` Sean Christopherson [this message]
2021-08-23 19:37 ` [PATCH 3/3] perf/x86/intel: Fold current_vcpu check into KVM's PT intr handler Sean Christopherson
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