linux-kernel - Re: [PATCH v10 098/108] KVM: TDX: Implement callbacks for MSR operations for TDX

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Date:   Thu, 12 Jan 2023 02:06:33 -0800
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     Ackerley Tng <ackerleytng@...gle.com>
Cc:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, 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

On Wed, Jan 04, 2023 at 01:20:13PM -0800,
Ackerley Tng <ackerleytng@...gle.com> wrote:

> 
> 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.

Nice catch. I'll fix it.
-- 
Isaku Yamahata <isaku.yamahata@...il.com>