linux-kernel - Re: [PATCH v5 2/2] kvm: nVMX: Introduce KVM_CAP_NESTED

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Date:   Wed, 18 Jul 2018 19:33:01 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     KarimAllah Ahmed <karahmed@...zon.de>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Jim Mattson <jmattson@...gle.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [PATCH v5 2/2] kvm: nVMX: Introduce KVM_CAP_NESTED_STATE

On 10/07/2018 11:27, KarimAllah Ahmed wrote:
> @@ -11772,7 +11772,6 @@ static int enter_vmx_non_root_mode(struct kvm_vcpu *vcpu)
>  	if (prepare_vmcs02(vcpu, vmcs12, &exit_qual))
>  		goto fail;
>  
> -	nested_get_vmcs12_pages(vcpu, vmcs12);
>  
>  	r = EXIT_REASON_MSR_LOAD_FAIL;
>  	msr_entry_idx = nested_vmx_load_msr(vcpu,

I think this is not enough, the MSR load should not be redone on
KVM_SET_NESTED_STATE.  This issue is preexisting and happens for SMM
exit as well.  SMM exit in fact also needs to defer
nested_get_vmcs12_pages, or the pages could be read from SMRAM.

I'll send a v6 patch and a testcase, and in the meanwhile I have applied
patch 1.

Paolo