linux-kernel - Re: [PATCH v3 3/3] KVM: x86: SGX must obey the KVM_INTERNAL_ERROR

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Date:   Fri, 30 Jul 2021 22:17:02 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     David Edmondson <david.edmondson@...cle.com>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>,
        Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org,
        Borislav Petkov <bp@...en8.de>,
        David Matlack <dmatlack@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH v3 3/3] KVM: x86: SGX must obey the
 KVM_INTERNAL_ERROR_EMULATION protocol

On Thu, Jul 29, 2021, David Edmondson wrote:
> When passing the failing address and size out to user space, SGX must
> ensure not to trample on the earlier fields of the emulation_failure
> sub-union of struct kvm_run.
> 
> Signed-off-by: David Edmondson <david.edmondson@...cle.com>
> ---
>  arch/x86/kvm/vmx/sgx.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/sgx.c b/arch/x86/kvm/vmx/sgx.c
> index 6693ebdc0770..63fb93163383 100644
> --- a/arch/x86/kvm/vmx/sgx.c
> +++ b/arch/x86/kvm/vmx/sgx.c
> @@ -53,11 +53,9 @@ static int sgx_get_encls_gva(struct kvm_vcpu *vcpu, unsigned long offset,
>  static void sgx_handle_emulation_failure(struct kvm_vcpu *vcpu, u64 addr,
>  					 unsigned int size)
>  {
> -	vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
> -	vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
> -	vcpu->run->internal.ndata = 2;
> -	vcpu->run->internal.data[0] = addr;
> -	vcpu->run->internal.data[1] = size;
> +	uint64_t data[2] = { addr, size };
> +
> +	kvm_prepare_emulation_failure_exit(vcpu, false, data, sizeof(data));

Assuming we go with my suggestion to have kvm_prepare_emulation_failure_exit()
capture the exit reason/info, it's probably worth converting all the
KVM_EXIT_INTERNAL_ERROR paths in sgx.c, even though the others don't clobber flags.