linux-kernel - Re: [RFC PATCH 23/35] KVM: SVM: Add support for CR4 write traps for an SEV-ES guest

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Message-ID: <20200914221651.GK7192@sjchrist-ice>
Date:   Mon, 14 Sep 2020 15:16:51 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [RFC PATCH 23/35] KVM: SVM: Add support for CR4 write traps for
 an SEV-ES guest

On Mon, Sep 14, 2020 at 03:15:37PM -0500, Tom Lendacky wrote:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 6f5988c305e1..5e5f1e8fed3a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1033,6 +1033,26 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
>  }
>  EXPORT_SYMBOL_GPL(kvm_set_cr4);
>  
> +int kvm_track_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
> +{
> +	unsigned long old_cr4 = kvm_read_cr4(vcpu);
> +	unsigned long pdptr_bits = X86_CR4_PGE | X86_CR4_PSE | X86_CR4_PAE |
> +				   X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_PKE;
> +
> +	if (kvm_x86_ops.set_cr4(vcpu, cr4))
> +		return 1;

Pretty much all the same comments as EFER and CR0, e.g. call svm_set_cr4()
directly instead of bouncing through kvm_x86_ops.  And with that, this can
be called __kvm_set_cr4() to be consistent with __kvm_set_cr0().

> +
> +	if (((cr4 ^ old_cr4) & pdptr_bits) ||
> +	    (!(cr4 & X86_CR4_PCIDE) && (old_cr4 & X86_CR4_PCIDE)))
> +		kvm_mmu_reset_context(vcpu);
> +
> +	if ((cr4 ^ old_cr4) & (X86_CR4_OSXSAVE | X86_CR4_PKE))
> +		kvm_update_cpuid_runtime(vcpu);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(kvm_track_cr4);
> +
>  int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
>  {
>  	bool skip_tlb_flush = false;
> -- 
> 2.28.0
>