linux-kernel - Re: [RFC PATCH v5 102/104] KVM: TDX: Add methods to ignore accesses to CPU state

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Message-ID: <ec60ba8e-3ed9-1d06-d8c2-4db9529daf93@intel.com>
Date:   Tue, 12 Apr 2022 14:49:20 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 102/104] KVM: TDX: Add methods to ignore accesses
 to CPU state

On 3/5/2022 3:49 AM, isaku.yamahata@...el.com wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
> 
> TDX protects TDX guest state from VMM.  Implements to access methods for
> TDX guest state to ignore them or return zero.
> 

...

> +void tdx_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
> +{
> +	kvm_register_mark_available(vcpu, reg);
> +	switch (reg) {
> +	case VCPU_REGS_RSP:
> +	case VCPU_REGS_RIP:
> +	case VCPU_EXREG_PDPTR:
> +	case VCPU_EXREG_CR0:
> +	case VCPU_EXREG_CR3:
> +	case VCPU_EXREG_CR4:
> +		break;
> +	default:
> +		KVM_BUG_ON(1, vcpu->kvm);
> +		break;
> +	}
> +}

Isaku,

We missed one case that some GPRs are accessible by KVM/userspace for 
TDVMCALL exit.