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Message-ID: <diqz5ydmov3m.fsf@google.com>
Date:   Wed, 04 Jan 2023 13:20:13 -0800
From:   Ackerley Tng <ackerleytng@...gle.com>
To:     isaku.yamahata@...el.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        pbonzini@...hat.com, erdemaktas@...gle.com, seanjc@...gle.com,
        sagis@...gle.com, dmatlack@...gle.com
Subject: Re: [PATCH v10 098/108] KVM: TDX: Implement callbacks for MSR
 operations for TDX


I believe we should also have a handler for .msr_filter_changed.

Without an .msr_filter_changed handler, a host crash can occur if we
first set up a vcpu for the TD, and then set an MSR filter.

If we first set up a vcpu for the TD, and then set an MSR filter, upon
vcpu_enter_guest, the .msr_filter_changed handler (currently
vmx_msr_filter_changed()) will be invoked. to_vmx(vcpu) interprets the
containing struct of struct kvm_vcpu to be a struct vcpu_vmx instead of
a struct vcpu_tdx.

In my case, I was working on a selftest and the missing handler caused a
NULL dereference in vmx_disable_intercept_for_msr() because
vmx->vmcs01.msr_bitmap is NULL.

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