linux-kernel - Re: [PATCH v7 050/102] KVM: VMX: Split out guts of EPT violation to common/exposed function

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Date:   Fri, 08 Jul 2022 22:25:05 +1200
From:   Kai Huang <kai.huang@...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>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v7 050/102] KVM: VMX: Split out guts of EPT violation to
 common/exposed function

On Mon, 2022-06-27 at 14:53 -0700, isaku.yamahata@...el.com wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
> 
> The difference of TDX EPT violation is how to retrieve information, GPA,
> and exit qualification.  To share the code to handle EPT violation, split
> out the guts of EPT violation handler so that VMX/TDX exit handler can call
> it after retrieving GPA and exit qualification.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/vmx/common.h | 33 +++++++++++++++++++++++++++++++++
>  arch/x86/kvm/vmx/vmx.c    | 32 ++++++--------------------------
>  2 files changed, 39 insertions(+), 26 deletions(-)
>  create mode 100644 arch/x86/kvm/vmx/common.h
> 
> diff --git a/arch/x86/kvm/vmx/common.h b/arch/x86/kvm/vmx/common.h
> new file mode 100644
> index 000000000000..235908f3e044
> --- /dev/null
> +++ b/arch/x86/kvm/vmx/common.h
> @@ -0,0 +1,33 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef __KVM_X86_VMX_COMMON_H
> +#define __KVM_X86_VMX_COMMON_H
> +
> +#include <linux/kvm_host.h>
> +
> +#include "mmu.h"
> +
> +static inline int __vmx_handle_ept_violation(struct kvm_vcpu *vcpu, gpa_t gpa,
> +					     unsigned long exit_qualification)
> +{
> +	u64 error_code;
> +
> +	/* Is it a read fault? */
> +	error_code = (exit_qualification & EPT_VIOLATION_ACC_READ)
> +		     ? PFERR_USER_MASK : 0;
> +	/* Is it a write fault? */
> +	error_code |= (exit_qualification & EPT_VIOLATION_ACC_WRITE)
> +		      ? PFERR_WRITE_MASK : 0;
> +	/* Is it a fetch fault? */
> +	error_code |= (exit_qualification & EPT_VIOLATION_ACC_INSTR)
> +		      ? PFERR_FETCH_MASK : 0;
> +	/* ept page table entry is present? */
> +	error_code |= (exit_qualification & EPT_VIOLATION_RWX_MASK)
> +		      ? PFERR_PRESENT_MASK : 0;
> +
> +	error_code |= (exit_qualification & EPT_VIOLATION_GVA_TRANSLATED) != 0 ?
> +	       PFERR_GUEST_FINAL_MASK : PFERR_GUEST_PAGE_MASK;
> +
> +	return kvm_mmu_page_fault(vcpu, gpa, error_code, NULL, 0);
> +}
> +
> +#endif /* __KVM_X86_VMX_COMMON_H */
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index e3d304b14df0..2f1dc06aec3c 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -50,6 +50,7 @@
>  #include <asm/vmx.h>
>  
>  #include "capabilities.h"
> +#include "common.h"
>  #include "cpuid.h"
>  #include "evmcs.h"
>  #include "hyperv.h"
> @@ -5578,11 +5579,10 @@ static int handle_task_switch(struct kvm_vcpu *vcpu)
>  
>  static int handle_ept_violation(struct kvm_vcpu *vcpu)
>  {
> -	unsigned long exit_qualification;
> -	gpa_t gpa;
> -	u64 error_code;
> +	unsigned long exit_qualification = vmx_get_exit_qual(vcpu);
> +	gpa_t gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS);
>  
> -	exit_qualification = vmx_get_exit_qual(vcpu);
> +	trace_kvm_page_fault(gpa, exit_qualification);
>  
>  	/*
>  	 * EPT violation happened while executing iret from NMI,
> @@ -5591,29 +5591,9 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
>  	 * AAK134, BY25.
>  	 */
>  	if (!(to_vmx(vcpu)->idt_vectoring_info & VECTORING_INFO_VALID_MASK) &&
> -			enable_vnmi &&
> -			(exit_qualification & INTR_INFO_UNBLOCK_NMI))
> +	    enable_vnmi && (exit_qualification & INTR_INFO_UNBLOCK_NMI))

Why this code change?

With this removed:

Reviewed-by: Kai Huang <kai.huang@...el.com>

>  		vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO, GUEST_INTR_STATE_NMI);
>  
> -	gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS);
> -	trace_kvm_page_fault(gpa, exit_qualification);
> -
> -	/* Is it a read fault? */
> -	error_code = (exit_qualification & EPT_VIOLATION_ACC_READ)
> -		     ? PFERR_USER_MASK : 0;
> -	/* Is it a write fault? */
> -	error_code |= (exit_qualification & EPT_VIOLATION_ACC_WRITE)
> -		      ? PFERR_WRITE_MASK : 0;
> -	/* Is it a fetch fault? */
> -	error_code |= (exit_qualification & EPT_VIOLATION_ACC_INSTR)
> -		      ? PFERR_FETCH_MASK : 0;
> -	/* ept page table entry is present? */
> -	error_code |= (exit_qualification & EPT_VIOLATION_RWX_MASK)
> -		      ? PFERR_PRESENT_MASK : 0;
> -
> -	error_code |= (exit_qualification & EPT_VIOLATION_GVA_TRANSLATED) != 0 ?
> -	       PFERR_GUEST_FINAL_MASK : PFERR_GUEST_PAGE_MASK;
> -
>  	vcpu->arch.exit_qualification = exit_qualification;
>  
>  	/*
> @@ -5627,7 +5607,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
>  	if (unlikely(allow_smaller_maxphyaddr && kvm_vcpu_is_illegal_gpa(vcpu, gpa)))
>  		return kvm_emulate_instruction(vcpu, 0);
>  
> -	return kvm_mmu_page_fault(vcpu, gpa, error_code, NULL, 0);
> +	return __vmx_handle_ept_violation(vcpu, gpa, exit_qualification);
>  }
>  
>  static int handle_ept_misconfig(struct kvm_vcpu *vcpu)