linux-kernel - Re: [PATCH V4 09/11] KVM: x86: Disable Intel Processor Trace when VMXON in L1 guest

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Message-ID: <69b9277e-e547-95e9-f220-958549f45ec1@redhat.com>
Date:   Tue, 9 Jan 2018 22:39:51 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jim Mattson <jmattson@...gle.com>,
        Luwei Kang <luwei.kang@...el.com>
Cc:     kvm list <kvm@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH V4 09/11] KVM: x86: Disable Intel Processor Trace when
 VMXON in L1 guest

On 09/01/2018 21:16, Jim Mattson wrote:
> This doesn't look right to me. pt_disable_intercept_for_msr calls
> either vmx_disable_intercept_for_msr or vmx_enable_intercept_for_msr,
> both of which only change vmx_msr_bitmap_legacy
> and vmx_msr_bitmap_longmode. Neither of these MSR permission bitmaps is
> likely to be the one in use by L1 (which is more likely to be using the
> mode-appropriate x2apic or x2apic_apicv bitmap). Moreover, these changes
> affect all of the VMs that are using those MSR permission bitmaps.

Yeah, I replied this morning with something like this, on the thread
about removing the longmode bitmaps.

Paolo