linux-kernel - Re: [PATCH v2 4/6] KVM: SVM: Handle MMIO during vectroing error

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Message-ID: <Z1nW4xTUjWry2qF4@google.com>
Date: Wed, 11 Dec 2024 10:16:03 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Ivan Orlov <iorlov@...zon.com>
Cc: bp@...en8.de, dave.hansen@...ux.intel.com, mingo@...hat.com, 
	pbonzini@...hat.com, shuah@...nel.org, tglx@...utronix.de, hpa@...or.com, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, x86@...nel.org, pdurrant@...zon.co.uk, 
	dwmw@...zon.co.uk
Subject: Re: [PATCH v2 4/6] KVM: SVM: Handle MMIO during vectroing error

On Mon, Nov 11, 2024, Ivan Orlov wrote:
> Handle MMIO during vectoring error in check_emulate_instruction to
> prevent infinite loop on SVM and eliminate the difference in how the
> situation when the guest accesses MMIO during vectoring is handled on
> SVM and VMX.
> 
> Signed-off-by: Ivan Orlov <iorlov@...zon.com>
> ---
> V1 -> V2:
> - Detect the unhandleable vectoring error in svm_check_emulate_instruction
> instead of handling it in the common MMU code (which is specific for
> cached MMIO)
> 
>  arch/x86/kvm/svm/svm.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index c1e29307826b..b69f0f98c576 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4797,9 +4797,16 @@ static void svm_enable_smi_window(struct kvm_vcpu *vcpu)
>  static int svm_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
>  					 void *insn, int insn_len)
>  {
> -	bool smep, smap, is_user;
> +	bool smep, smap, is_user, is_vect;
>  	u64 error_code;
>  
> +	is_vect = to_svm(vcpu)->vmcb->control.exit_int_info &
> +		  SVM_EXITINTINFO_TYPE_MASK;
> +
> +	/* Emulation is not possible when MMIO happens during event vectoring. */
> +	if (kvm_is_emul_type_mmio(emul_type) && is_vect)

Same nit here, omit the local variable.

> +		return X86EMUL_UNHANDLEABLE_VECTORING_IO;
> +
>  	/* Emulation is always possible when KVM has access to all guest state. */
>  	if (!sev_guest(vcpu->kvm))
>  		return X86EMUL_CONTINUE;
> -- 
> 2.43.0
>