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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.

  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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