linux-kernel - Re: [PATCH v3 2/6] KVM: VMX: Extend BUILD_CONTROLS

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Date:   Thu, 5 Aug 2021 22:32:56 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Zeng Guang <guang.zeng@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Kim Phillips <kim.phillips@....com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jethro Beekman <jethro@...tanix.com>,
        Kai Huang <kai.huang@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Robert Hu <robert.hu@...el.com>,
        Gao Chao <chao.gao@...el.com>,
        Robert Hoo <robert.hu@...ux.intel.com>
Subject: Re: [PATCH v3 2/6] KVM: VMX: Extend BUILD_CONTROLS_SHADOW macro to
 support 64-bit variation

On Thu, Aug 05, 2021, Zeng Guang wrote:
> From: Robert Hoo <robert.hu@...ux.intel.com>
> 
> The Tertiary VM-Exec Control, different from previous control fields, is 64
> bit. So extend BUILD_CONTROLS_SHADOW() by adding a 'bit' parameter, to
> support both 32 bit and 64 bit fields' auxiliary functions building.
> Also, define the auxiliary functions for Tertiary control field here, using
> the new BUILD_CONTROLS_SHADOW().
> 
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Robert Hoo <robert.hu@...ux.intel.com>
> ---
>  arch/x86/kvm/vmx/vmx.h | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index 3979a947933a..945c6639ce24 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -413,31 +413,32 @@ static inline u8 vmx_get_rvi(void)
>  	return vmcs_read16(GUEST_INTR_STATUS) & 0xff;
>  }
>  
> -#define BUILD_CONTROLS_SHADOW(lname, uname)				    \
> -static inline void lname##_controls_set(struct vcpu_vmx *vmx, u32 val)	    \
> +#define BUILD_CONTROLS_SHADOW(lname, uname, bits)			    \
> +static inline void lname##_controls_set(struct vcpu_vmx *vmx, u##bits val) \

Align the trailing backslashes (with tabs when possible).  It's a lot of unfortunate
churn, but it really does make the code easier to read.  An alternative is to split
"static inline" to a separate line.

>  {									    \
>  	if (vmx->loaded_vmcs->controls_shadow.lname != val) {		    \
> -		vmcs_write32(uname, val);				    \
> +		vmcs_write##bits(uname, val);				    \
>  		vmx->loaded_vmcs->controls_shadow.lname = val;		    \
>  	}								    \
>  }									    \
> -static inline u32 lname##_controls_get(struct vcpu_vmx *vmx)		    \
> +static inline u##bits lname##_controls_get(struct vcpu_vmx *vmx)	    \
>  {									    \
>  	return vmx->loaded_vmcs->controls_shadow.lname;			    \
>  }									    \
> -static inline void lname##_controls_setbit(struct vcpu_vmx *vmx, u32 val)   \
> +static inline void lname##_controls_setbit(struct vcpu_vmx *vmx, u##bits val)   \
>  {									    \
>  	lname##_controls_set(vmx, lname##_controls_get(vmx) | val);	    \
>  }									    \
> -static inline void lname##_controls_clearbit(struct vcpu_vmx *vmx, u32 val) \
> +static inline void lname##_controls_clearbit(struct vcpu_vmx *vmx, u##bits val) \
>  {									    \
>  	lname##_controls_set(vmx, lname##_controls_get(vmx) & ~val);	    \
>  }
> -BUILD_CONTROLS_SHADOW(vm_entry, VM_ENTRY_CONTROLS)
> -BUILD_CONTROLS_SHADOW(vm_exit, VM_EXIT_CONTROLS)
> -BUILD_CONTROLS_SHADOW(pin, PIN_BASED_VM_EXEC_CONTROL)
> -BUILD_CONTROLS_SHADOW(exec, CPU_BASED_VM_EXEC_CONTROL)
> -BUILD_CONTROLS_SHADOW(secondary_exec, SECONDARY_VM_EXEC_CONTROL)
> +BUILD_CONTROLS_SHADOW(vm_entry, VM_ENTRY_CONTROLS, 32)
> +BUILD_CONTROLS_SHADOW(vm_exit, VM_EXIT_CONTROLS, 32)
> +BUILD_CONTROLS_SHADOW(pin, PIN_BASED_VM_EXEC_CONTROL, 32)
> +BUILD_CONTROLS_SHADOW(exec, CPU_BASED_VM_EXEC_CONTROL, 32)
> +BUILD_CONTROLS_SHADOW(secondary_exec, SECONDARY_VM_EXEC_CONTROL, 32)
> +BUILD_CONTROLS_SHADOW(tertiary_exec, TERTIARY_VM_EXEC_CONTROL, 64)

This fails to compile because all the TERTIARY collateral is in a later patch.

I think I'd also prefer hiding the 32/64 param via more macros, e.g.

#define __BUILD_CONTROLS_SHADOW(lname, uname, bits)				\
static inline void lname##_controls_set(struct vcpu_vmx *vmx, u##bits val)	\
{										\
	if (vmx->loaded_vmcs->controls_shadow.lname != val) {			\
		vmcs_write##bits(uname, val);					\
		vmx->loaded_vmcs->controls_shadow.lname = val;			\
	}									\
}										\
static inline u##bits lname##_controls_get(struct vcpu_vmx *vmx)		\
{										\
	return vmx->loaded_vmcs->controls_shadow.lname;				\
}										\
static inline void lname##_controls_setbit(struct vcpu_vmx *vmx, u##bits val)	\
{										\
	lname##_controls_set(vmx, lname##_controls_get(vmx) | val);		\
}										\
static inline void lname##_controls_clearbit(struct vcpu_vmx *vmx, u##bits val)	\
{										\
	lname##_controls_set(vmx, lname##_controls_get(vmx) & ~val);		\
}
#define BUILD_CONTROLS_SHADOW(lname, uname)   __BUILD_CONTROLS_SHADOW(lname, uname, 32)
#define BUILD_CONTROLS_SHADOW64(lname, uname) __BUILD_CONTROLS_SHADOW(lname, uname, 64)