linux-kernel - Re: [PATCH 5/9] KVM: x86: Pass emulation type to can_emulate

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Message-ID: <4922135a-cbdf-f27c-5408-ccbecc623130@oracle.com>
Date:   Thu, 20 Jan 2022 14:38:05 +0000
From:   Liam Merwick <liam.merwick@...cle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Brijesh Singh <brijesh.singh@....com>,
        Liam Merwick <liam.merwick@...cle.com>
Subject: Re: [PATCH 5/9] KVM: x86: Pass emulation type to
 can_emulate_instruction()

On 20/01/2022 01:07, Sean Christopherson wrote:
> Pass the emulation type to kvm_x86_ops.can_emulate_insutrction() so that

typo in function name - should be can_emulate_instruction()

> a future commit can harden KVM's SEV support to WARN on emulation
> scenarios that should never happen.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>


Reviewed-by: Liam Merwick <liam.merwick@...cle.com>


> ---
>   arch/x86/include/asm/kvm_host.h |  3 ++-
>   arch/x86/kvm/svm/svm.c          |  3 ++-
>   arch/x86/kvm/vmx/vmx.c          |  7 ++++---
>   arch/x86/kvm/x86.c              | 11 +++++++++--
>   4 files changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 682ad02a4e58..c890931c9c65 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1482,7 +1482,8 @@ struct kvm_x86_ops {
>   
>   	int (*get_msr_feature)(struct kvm_msr_entry *entry);
>   
> -	bool (*can_emulate_instruction)(struct kvm_vcpu *vcpu, void *insn, int insn_len);
> +	bool (*can_emulate_instruction)(struct kvm_vcpu *vcpu, int emul_type,
> +					void *insn, int insn_len);
>   
>   	bool (*apic_init_signal_blocked)(struct kvm_vcpu *vcpu);
>   	int (*enable_direct_tlbflush)(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index edea52be6c01..994224ae2731 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4257,7 +4257,8 @@ static void svm_enable_smi_window(struct kvm_vcpu *vcpu)
>   	}
>   }
>   
> -static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, void *insn, int insn_len)
> +static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
> +					void *insn, int insn_len)
>   {
>   	bool smep, smap, is_user;
>   	unsigned long cr4;
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index a02a28ce7cc3..4b4c1dfa6842 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1487,11 +1487,12 @@ static int vmx_rtit_ctl_check(struct kvm_vcpu *vcpu, u64 data)
>   	return 0;
>   }
>   
> -static bool vmx_can_emulate_instruction(struct kvm_vcpu *vcpu, void *insn, int insn_len)
> +static bool vmx_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
> +					void *insn, int insn_len)
>   {
>   	/*
>   	 * Emulation of instructions in SGX enclaves is impossible as RIP does
> -	 * not point  tthe failing instruction, and even if it did, the code
> +	 * not point at the failing instruction, and even if it did, the code
>   	 * stream is inaccessible.  Inject #UD instead of exiting to userspace
>   	 * so that guest userspace can't DoS the guest simply by triggering
>   	 * emulation (enclaves are CPL3 only).
> @@ -5397,7 +5398,7 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu)
>   {
>   	gpa_t gpa;
>   
> -	if (!vmx_can_emulate_instruction(vcpu, NULL, 0))
> +	if (!vmx_can_emulate_instruction(vcpu, EMULTYPE_PF, NULL, 0))
>   		return 1;
>   
>   	/*
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 55518b7d3b96..2fa4687de8e4 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6810,6 +6810,13 @@ int kvm_write_guest_virt_system(struct kvm_vcpu *vcpu, gva_t addr, void *val,
>   }
>   EXPORT_SYMBOL_GPL(kvm_write_guest_virt_system);
>   
> +static int kvm_can_emulate_insn(struct kvm_vcpu *vcpu, int emul_type,
> +				void *insn, int insn_len)
> +{
> +	return static_call(kvm_x86_can_emulate_instruction)(vcpu, emul_type,
> +							    insn, insn_len);
> +}
> +
>   int handle_ud(struct kvm_vcpu *vcpu)
>   {
>   	static const char kvm_emulate_prefix[] = { __KVM_EMULATE_PREFIX };
> @@ -6817,7 +6824,7 @@ int handle_ud(struct kvm_vcpu *vcpu)
>   	char sig[5]; /* ud2; .ascii "kvm" */
>   	struct x86_exception e;
>   
> -	if (unlikely(!static_call(kvm_x86_can_emulate_instruction)(vcpu, NULL, 0)))
> +	if (unlikely(!kvm_can_emulate_insn(vcpu, emul_type, NULL, 0)))
>   		return 1;
>   
>   	if (force_emulation_prefix &&
> @@ -8193,7 +8200,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>   	bool writeback = true;
>   	bool write_fault_to_spt;
>   
> -	if (unlikely(!static_call(kvm_x86_can_emulate_instruction)(vcpu, insn, insn_len)))
> +	if (unlikely(!kvm_can_emulate_insn(vcpu, emulation_type, insn, insn_len)))
>   		return 1;
>   
>   	vcpu->arch.l1tf_flush_l1d = true;