linux-kernel - Re: [PATCH] KVM: nVMX: Reset vmxon

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Date:   Thu, 9 Sep 2021 16:20:35 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Yu Zhang <yu.c.zhang@...ux.intel.com>
Cc:     pbonzini@...hat.com, vkuznets@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org
Subject: Re: [PATCH] KVM: nVMX: Reset vmxon_ptr upon VMXOFF emulation.

On Thu, Sep 09, 2021, Yu Zhang wrote:
> From: Vitaly Kuznetsov <vkuznets@...hat.com>
> 
> Currently, 'vmx->nested.vmxon_ptr' is not reset upon VMXOFF
> emulation. This is not a problem per se as we never access
> it when !vmx->nested.vmxon. But this should be done to avoid
> any issue in the future.
> 
> Also, initialize the vmxon_ptr when vcpu is created.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> Signed-off-by: Yu Zhang <yu.c.zhang@...ux.intel.com>
> ---
>  arch/x86/kvm/vmx/nested.c | 1 +
>  arch/x86/kvm/vmx/vmx.c    | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 90f34f12f883..e4260f67caac 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -289,6 +289,7 @@ static void free_nested(struct kvm_vcpu *vcpu)
>  	kvm_clear_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu);
>  
>  	vmx->nested.vmxon = false;
> +	vmx->nested.vmxon_ptr = -1ull;

Looks like the "-1ull" comes from current_vmptr and friends, but using INVALID_GPA
is more appropriate.  It's the same value, but less arbitrary.  The other usage of
-1ull for guest physical addresses should really be cleaned up, too.