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From: Andy Lutomirski <luto@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Xiaoyao Li <xiaoyao.li@intel.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	X86 ML <x86@kernel.org>, kvm list <kvm@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	David Laight <David.Laight@aculab.com>
Subject: Re: [PATCH v2 5/6] kvm: x86: Emulate MSR IA32_CORE_CAPABILITIES
Date: Mon, 10 Feb 2020 19:52:13 -0800	[thread overview]
Message-ID: <CALCETrUAsUzqLhhNkLSC2612odskjqPQvj4uXgBOaoBGoCQD0A@mail.gmail.com> (raw)
In-Reply-To: <20200204093725.GC14879@hirez.programming.kicks-ass.net>

On Tue, Feb 4, 2020 at 1:37 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Tue, Feb 04, 2020 at 05:19:26PM +0800, Xiaoyao Li wrote:
>
> > > > + case MSR_IA32_CORE_CAPS:
> > > > +         if (!msr_info->host_initiated)
> > >
> > > Shouldn't @data be checked against kvm_get_core_capabilities()?
> >
> > Maybe it's for the case that userspace might have the ability to emulate SLD
> > feature? And we usually let userspace set whatever it wants, e.g.,
> > ARCH_CAPABILITIES.
>
> If the 'sq_misc.split_lock' event is sufficiently accurate, I suppose
> the host could use that to emulate the feature at the cost of one
> counter used.

I would be impressed if the event were to fire before executing the
offending split lock.  Wouldn't the best possible result be for it to
fire with RIP pointing to the *next* instruction?  This seems like it
could be quite confusing to a guest.

  reply	other threads:[~2020-02-11  3:52 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-03 15:16 [PATCH v2 0/6] kvm/split_lock: Add feature split lock detection support in kvm Xiaoyao Li
2020-02-03 15:16 ` [PATCH v2 1/6] x86/split_lock: Add and export get_split_lock_detect_state() Xiaoyao Li
2020-02-03 21:45   ` Sean Christopherson
2020-02-03 15:16 ` [PATCH v2 2/6] x86/split_lock: Add and export split_lock_detect_set() Xiaoyao Li
2020-02-03 15:16 ` [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write Xiaoyao Li
2020-02-03 20:54   ` Sean Christopherson
2020-02-04  2:55     ` Xiaoyao Li
2020-02-11 12:20   ` Paolo Bonzini
2020-02-11 13:22     ` Thomas Gleixner
2020-02-11 13:34       ` Paolo Bonzini
2020-02-11 14:02         ` Xiaoyao Li
2020-02-11 14:34           ` David Laight
2020-02-27  0:11         ` Sean Christopherson
2020-03-12 11:42           ` Xiaoyao Li
2020-03-12 15:00             ` Paolo Bonzini
2020-02-03 15:16 ` [PATCH v2 4/6] kvm: vmx: Extend VMX's #AC handding for split lock in guest Xiaoyao Li
2020-02-03 21:14   ` Sean Christopherson
2020-02-04  6:46     ` Xiaoyao Li
2020-02-10 21:30       ` Sean Christopherson
2020-02-03 15:16 ` [PATCH v2 5/6] kvm: x86: Emulate MSR IA32_CORE_CAPABILITIES Xiaoyao Li
2020-02-03 21:43   ` Sean Christopherson
2020-02-04  9:19     ` Xiaoyao Li
2020-02-04  9:37       ` Peter Zijlstra
2020-02-11  3:52         ` Andy Lutomirski [this message]
2020-02-11 12:38           ` Peter Zijlstra
2020-02-03 15:16 ` [PATCH v2 6/6] x86: vmx: virtualize split lock detection Xiaoyao Li
2020-02-03 15:58   ` Xiaoyao Li
2020-02-03 18:52   ` Andy Lutomirski
2020-02-03 21:42   ` Sean Christopherson
2020-02-04  2:52     ` Xiaoyao Li
2020-02-04  5:35       ` Sean Christopherson

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