linux-kernel - Re: [PATCH] KVM: VMX: Cache IA32

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Message-ID: <5045320c-3036-4e08-140e-4bb5cf78be24@redhat.com>
Date:   Wed, 29 Nov 2017 23:26:30 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Andi Kleen <ak@...ux.intel.com>, Wanpeng Li <kernellwp@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH] KVM: VMX: Cache IA32_DEBUGCTL in memory

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