Re: [PATCH v2 09/15] KVM: x86: Drop non-raw kvm_<reg>_write() helpers

[Binbin Wu <binbin.wu@linux.intel.com>]

On 5/15/2026 5:53 AM, Sean Christopherson wrote:
> Drop the non-raw, mode-aware kvm_<reg>_write() helpers as there is no
> usage in KVM, and in all likelihood there will never be usage in KVM as
> use of hardcoded registers in instructions is uncommon, and *modifying*
> hardcoded registers is practically unheard of.  While there are a few
> instructions that modify registers in mode-aware ways, e.g. REP string
> and some ENCLS varieties, the odds of KVM needing to emulate such
> instructions (outside of the fully emulator) are vanishingly small.
> 
> Drop kvm_<reg>_write() to prevent incorrect usage; _if_ a new instruction
> comes along that needs to modify a hardcoded register, this can be
> reverted.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>

> ---
>  arch/x86/kvm/regs.h | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/regs.h b/arch/x86/kvm/regs.h
> index b28e71caed25..52bed14f43e3 100644
> --- a/arch/x86/kvm/regs.h
> +++ b/arch/x86/kvm/regs.h
> @@ -61,11 +61,6 @@ static __always_inline unsigned long kvm_##lname##_read(struct kvm_vcpu *vcpu)
>  {											\
>  	return vcpu->arch.regs[VCPU_REGS_##uname] & kvm_reg_mode_mask(vcpu);		\
>  }											\
> -static __always_inline void kvm_##lname##_write(struct kvm_vcpu *vcpu,			\
> -						unsigned long val)			\
> -{											\
> -	vcpu->arch.regs[VCPU_REGS_##uname] = val & kvm_reg_mode_mask(vcpu);		\
> -}											\
>  static __always_inline unsigned long kvm_##lname##_read_raw(struct kvm_vcpu *vcpu)	\
>  {											\
>  	return vcpu->arch.regs[VCPU_REGS_##uname];					\