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Date: Thu, 13 Jun 2024 11:16:21 -0700
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Message-ID: <Zms3dVgcuObZOwRR@google.com>
Subject: Re: [PATCH v2 18/25] KVM: nVMX: Add a prerequisite to
 SHADOW_FIELD_R[OW] macros
From: Sean Christopherson <seanjc@google.com>
To: Xin Li <xin3.li@intel.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, 
	linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, 
	pbonzini@redhat.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, 
	bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, 
	shuah@kernel.org, vkuznets@redhat.com, peterz@infradead.org, 
	ravi.v.shankar@intel.com, xin@zytor.com
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On Wed, Feb 07, 2024, Xin Li wrote:
> @@ -32,48 +32,48 @@ BUILD_BUG_ON(1)
>   */
>  
>  /* 16-bits */
> -SHADOW_FIELD_RW(GUEST_INTR_STATUS, guest_intr_status)
> -SHADOW_FIELD_RW(GUEST_PML_INDEX, guest_pml_index)
> -SHADOW_FIELD_RW(HOST_FS_SELECTOR, host_fs_selector)
> -SHADOW_FIELD_RW(HOST_GS_SELECTOR, host_gs_selector)
> +SHADOW_FIELD_RW(GUEST_INTR_STATUS, guest_intr_status, cpu_has_vmx_apicv())
> +SHADOW_FIELD_RW(GUEST_PML_INDEX, guest_pml_index, cpu_has_vmx_pml())
> +SHADOW_FIELD_RW(HOST_FS_SELECTOR, host_fs_selector, true)
> +SHADOW_FIELD_RW(HOST_GS_SELECTOR, host_gs_selector, true)
>  
>  /* 32-bits */
> -SHADOW_FIELD_RO(VM_EXIT_REASON, vm_exit_reason)
> -SHADOW_FIELD_RO(VM_EXIT_INTR_INFO, vm_exit_intr_info)
> -SHADOW_FIELD_RO(VM_EXIT_INSTRUCTION_LEN, vm_exit_instruction_len)
> -SHADOW_FIELD_RO(IDT_VECTORING_INFO_FIELD, idt_vectoring_info_field)
> -SHADOW_FIELD_RO(IDT_VECTORING_ERROR_CODE, idt_vectoring_error_code)
> -SHADOW_FIELD_RO(VM_EXIT_INTR_ERROR_CODE, vm_exit_intr_error_code)
> -SHADOW_FIELD_RO(GUEST_CS_AR_BYTES, guest_cs_ar_bytes)
> -SHADOW_FIELD_RO(GUEST_SS_AR_BYTES, guest_ss_ar_bytes)
> -SHADOW_FIELD_RW(CPU_BASED_VM_EXEC_CONTROL, cpu_based_vm_exec_control)
> -SHADOW_FIELD_RW(PIN_BASED_VM_EXEC_CONTROL, pin_based_vm_exec_control)
> -SHADOW_FIELD_RW(EXCEPTION_BITMAP, exception_bitmap)
> -SHADOW_FIELD_RW(VM_ENTRY_EXCEPTION_ERROR_CODE, vm_entry_exception_error_code)
> -SHADOW_FIELD_RW(VM_ENTRY_INTR_INFO_FIELD, vm_entry_intr_info_field)
> -SHADOW_FIELD_RW(VM_ENTRY_INSTRUCTION_LEN, vm_entry_instruction_len)
> -SHADOW_FIELD_RW(TPR_THRESHOLD, tpr_threshold)
> -SHADOW_FIELD_RW(GUEST_INTERRUPTIBILITY_INFO, guest_interruptibility_info)
> -SHADOW_FIELD_RW(VMX_PREEMPTION_TIMER_VALUE, vmx_preemption_timer_value)
> +SHADOW_FIELD_RO(VM_EXIT_REASON, vm_exit_reason, true)
> +SHADOW_FIELD_RO(VM_EXIT_INTR_INFO, vm_exit_intr_info, true)
> +SHADOW_FIELD_RO(VM_EXIT_INSTRUCTION_LEN, vm_exit_instruction_len, true)
> +SHADOW_FIELD_RO(VM_EXIT_INTR_ERROR_CODE, vm_exit_intr_error_code, true)
> +SHADOW_FIELD_RO(IDT_VECTORING_INFO_FIELD, idt_vectoring_info_field, true)
> +SHADOW_FIELD_RO(IDT_VECTORING_ERROR_CODE, idt_vectoring_error_code, true)
> +SHADOW_FIELD_RO(GUEST_CS_AR_BYTES, guest_cs_ar_bytes, true)
> +SHADOW_FIELD_RO(GUEST_SS_AR_BYTES, guest_ss_ar_bytes, true)
> +SHADOW_FIELD_RW(CPU_BASED_VM_EXEC_CONTROL, cpu_based_vm_exec_control, true)
> +SHADOW_FIELD_RW(PIN_BASED_VM_EXEC_CONTROL, pin_based_vm_exec_control, true)
> +SHADOW_FIELD_RW(EXCEPTION_BITMAP, exception_bitmap, true)
> +SHADOW_FIELD_RW(VM_ENTRY_EXCEPTION_ERROR_CODE, vm_entry_exception_error_code, true)
> +SHADOW_FIELD_RW(VM_ENTRY_INTR_INFO_FIELD, vm_entry_intr_info_field, true)
> +SHADOW_FIELD_RW(VM_ENTRY_INSTRUCTION_LEN, vm_entry_instruction_len, true)
> +SHADOW_FIELD_RW(TPR_THRESHOLD, tpr_threshold, true)
> +SHADOW_FIELD_RW(GUEST_INTERRUPTIBILITY_INFO, guest_interruptibility_info, true)
> +SHADOW_FIELD_RW(VMX_PREEMPTION_TIMER_VALUE, vmx_preemption_timer_value, cpu_has_vmx_preemption_timer())
>  
>  /* Natural width */
> -SHADOW_FIELD_RO(EXIT_QUALIFICATION, exit_qualification)
> -SHADOW_FIELD_RO(GUEST_LINEAR_ADDRESS, guest_linear_address)
> -SHADOW_FIELD_RW(GUEST_RIP, guest_rip)
> -SHADOW_FIELD_RW(GUEST_RSP, guest_rsp)
> -SHADOW_FIELD_RW(GUEST_CR0, guest_cr0)
> -SHADOW_FIELD_RW(GUEST_CR3, guest_cr3)
> -SHADOW_FIELD_RW(GUEST_CR4, guest_cr4)
> -SHADOW_FIELD_RW(GUEST_RFLAGS, guest_rflags)
> -SHADOW_FIELD_RW(CR0_GUEST_HOST_MASK, cr0_guest_host_mask)
> -SHADOW_FIELD_RW(CR0_READ_SHADOW, cr0_read_shadow)
> -SHADOW_FIELD_RW(CR4_READ_SHADOW, cr4_read_shadow)
> -SHADOW_FIELD_RW(HOST_FS_BASE, host_fs_base)
> -SHADOW_FIELD_RW(HOST_GS_BASE, host_gs_base)
> +SHADOW_FIELD_RO(EXIT_QUALIFICATION, exit_qualification, true)
> +SHADOW_FIELD_RO(GUEST_LINEAR_ADDRESS, guest_linear_address, true)
> +SHADOW_FIELD_RW(GUEST_RIP, guest_rip, true)
> +SHADOW_FIELD_RW(GUEST_RSP, guest_rsp, true)
> +SHADOW_FIELD_RW(GUEST_CR0, guest_cr0, true)
> +SHADOW_FIELD_RW(GUEST_CR3, guest_cr3, true)
> +SHADOW_FIELD_RW(GUEST_CR4, guest_cr4, true)
> +SHADOW_FIELD_RW(GUEST_RFLAGS, guest_rflags, true)
> +SHADOW_FIELD_RW(CR0_GUEST_HOST_MASK, cr0_guest_host_mask, true)
> +SHADOW_FIELD_RW(CR0_READ_SHADOW, cr0_read_shadow, true)
> +SHADOW_FIELD_RW(CR4_READ_SHADOW, cr4_read_shadow, true)
> +SHADOW_FIELD_RW(HOST_FS_BASE, host_fs_base, true)
> +SHADOW_FIELD_RW(HOST_GS_BASE, host_gs_base, true)
>  
>  /* 64-bit */
> -SHADOW_FIELD_RO(GUEST_PHYSICAL_ADDRESS, guest_physical_address)
> -SHADOW_FIELD_RO(GUEST_PHYSICAL_ADDRESS_HIGH, guest_physical_address)
> +SHADOW_FIELD_RO(GUEST_PHYSICAL_ADDRESS, guest_physical_address, true)
> +SHADOW_FIELD_RO(GUEST_PHYSICAL_ADDRESS_HIGH, guest_physical_address, true)

This is not a net postive for readability or maintability.  I don't hate the
idea, it just needs MOAR MACROs :-)  E.g. add a layer for the common case where
the field unconditionally exists.

#ifndef __SHADOW_FIELD_RO
#define __SHADOW_FIELD_RO(x, y, c)
#endif
#ifndef __SHADOW_FIELD_RW
#define __SHADOW_FIELD_RW(x, y, c)
#endif

#define SHADOW_FIELD_RO(x, y) __SHADOW_FIELD_RO(x, y, true)
#define SHADOW_FIELD_RW(x, y) __SHADOW_FIELD_RW(x, y, true)