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Subject: Re: [PATCH] KVM: VMX: Cache IA32_DEBUGCTL in memory
To: Andi Kleen <ak@linux.intel.com>, Wanpeng Li <kernellwp@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Wanpeng Li <wanpeng.li@hotmail.com>, Jim Mattson <jmattson@google.com>
References: <1511935673-7371-1-git-send-email-wanpeng.li@hotmail.com>
 <87fu8xj69o.fsf@linux.intel.com>
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <5045320c-3036-4e08-140e-4bb5cf78be24@redhat.com>
Date: Wed, 29 Nov 2017 23:26:30 +0100
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On 29/11/2017 19:20, Andi Kleen wrote:
> But I haven't looked too closely, but I suspect you'll clobber global
> kernel debugger state this way.

I checked all callers of update_debugctlmsr, and couldn't find any that
could run asynchronously while KVM is caching the value.  For example
__switch_to_xtra would always run before the sched_in notifier.

Thanks,

Paolo