Re: [PATCH v4 08/40] KVM: arm/arm64: Introduce vcpu_el1_is_32bit

[Marc Zyngier <marc.zyngier@arm.com>]

On Thu, 15 Feb 2018 21:03:00 +0000,
Christoffer Dall wrote:
> 
> We have numerous checks around that checks if the HCR_EL2 has the RW bit
> set to figure out if we're running an AArch64 or AArch32 VM.  In some
> cases, directly checking the RW bit (given its unintuitive name), is a
> bit confusing, and that's not going to improve as we move logic around
> for the following patches that optimize KVM on AArch64 hosts with VHE.
> 
> Therefore, introduce a helper, vcpu_el1_is_32bit, and replace existing
> direct checks of HCR_EL2.RW with the helper.
> 
> Reviewed-by: Julien Grall <julien.grall@arm.com>
> Reviewed-by: Julien Thierry <julien.thierry@arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> ---
> 
> Notes:
>     Changes since v2:
>      - New patch
>     
>     Changes since v1:
>      - Reworded comments as suggested by Drew
> 
>  arch/arm64/include/asm/kvm_emulate.h |  7 ++++++-
>  arch/arm64/kvm/hyp/switch.c          | 11 +++++------
>  arch/arm64/kvm/hyp/sysreg-sr.c       |  5 +++--
>  arch/arm64/kvm/inject_fault.c        |  6 +++---
>  4 files changed, 17 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index 9ee316b962c8..3cc535591bdf 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -45,6 +45,11 @@ void kvm_inject_undef32(struct kvm_vcpu *vcpu);
>  void kvm_inject_dabt32(struct kvm_vcpu *vcpu, unsigned long addr);
>  void kvm_inject_pabt32(struct kvm_vcpu *vcpu, unsigned long addr);
>  
> +static inline bool vcpu_el1_is_32bit(struct kvm_vcpu *vcpu)
> +{
> +	return !(vcpu->arch.hcr_el2 & HCR_RW);
> +}
> +
>  static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>  {
>  	vcpu->arch.hcr_el2 = HCR_GUEST_FLAGS;
> @@ -65,7 +70,7 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>  	 * For now this is conditional, since no AArch32 feature regs
>  	 * are currently virtualised.
>  	 */
> -	if (vcpu->arch.hcr_el2 & HCR_RW)
> +	if (!vcpu_el1_is_32bit(vcpu))
>  		vcpu->arch.hcr_el2 |= HCR_TID3;
>  }
>  
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index b51638490d85..fbab9752a9f4 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -74,7 +74,7 @@ static hyp_alternate_select(__activate_traps_arch,
>  
>  static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
>  {
> -	u64 val;
> +	u64 hcr = vcpu->arch.hcr_el2;
>  
>  	/*
>  	 * We are about to set CPTR_EL2.TFP to trap all floating point
> @@ -85,17 +85,16 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
>  	 * If FP/ASIMD is not implemented, FPEXC is UNDEFINED and any access to
>  	 * it will cause an exception.
>  	 */
> -	val = vcpu->arch.hcr_el2;
> -
> -	if (!(val & HCR_RW) && system_supports_fpsimd()) {
> +	if (vcpu_el1_is_32bit(vcpu) && system_supports_fpsimd()) {
>  		write_sysreg(1 << 30, fpexc32_el2);
>  		isb();
>  	}
> -	write_sysreg(val, hcr_el2);
>  
> -	if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN) && (val & HCR_VSE))
> +	if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN) && (hcr & HCR_VSE))
>  		write_sysreg_s(vcpu->arch.vsesr_el2, SYS_VSESR_EL2);
>  
> +	write_sysreg(hcr, hcr_el2);
> +
>  	/* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
>  	write_sysreg(1 << 15, hstr_el2);
>  	/*
> diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
> index 434f0fc9cfb3..99fc60516103 100644
> --- a/arch/arm64/kvm/hyp/sysreg-sr.c
> +++ b/arch/arm64/kvm/hyp/sysreg-sr.c
> @@ -19,6 +19,7 @@
>  #include <linux/kvm_host.h>
>  
>  #include <asm/kvm_asm.h>
> +#include <asm/kvm_emulate.h>
>  #include <asm/kvm_hyp.h>
>  
>  /* Yes, this does nothing, on purpose */
> @@ -147,7 +148,7 @@ void __hyp_text __sysreg32_save_state(struct kvm_vcpu *vcpu)
>  {
>  	u64 *spsr, *sysreg;
>  
> -	if (read_sysreg(hcr_el2) & HCR_RW)
> +	if (!vcpu_el1_is_32bit(vcpu))
>  		return;
>  
>  	spsr = vcpu->arch.ctxt.gp_regs.spsr;
> @@ -172,7 +173,7 @@ void __hyp_text __sysreg32_restore_state(struct kvm_vcpu *vcpu)
>  {
>  	u64 *spsr, *sysreg;
>  
> -	if (read_sysreg(hcr_el2) & HCR_RW)
> +	if (!vcpu_el1_is_32bit(vcpu))
>  		return;
>  
>  	spsr = vcpu->arch.ctxt.gp_regs.spsr;
> diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
> index c1e179d34e6a..30a3f58cdb7b 100644
> --- a/arch/arm64/kvm/inject_fault.c
> +++ b/arch/arm64/kvm/inject_fault.c
> @@ -128,7 +128,7 @@ static void inject_undef64(struct kvm_vcpu *vcpu)
>   */
>  void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr)
>  {
> -	if (!(vcpu->arch.hcr_el2 & HCR_RW))
> +	if (vcpu_el1_is_32bit(vcpu))
>  		kvm_inject_dabt32(vcpu, addr);
>  	else
>  		inject_abt64(vcpu, false, addr);
> @@ -144,7 +144,7 @@ void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr)
>   */
>  void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr)
>  {
> -	if (!(vcpu->arch.hcr_el2 & HCR_RW))
> +	if (vcpu_el1_is_32bit(vcpu))
>  		kvm_inject_pabt32(vcpu, addr);
>  	else
>  		inject_abt64(vcpu, true, addr);
> @@ -158,7 +158,7 @@ void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr)
>   */
>  void kvm_inject_undefined(struct kvm_vcpu *vcpu)
>  {
> -	if (!(vcpu->arch.hcr_el2 & HCR_RW))
> +	if (vcpu_el1_is_32bit(vcpu))
>  		kvm_inject_undef32(vcpu);
>  	else
>  		inject_undef64(vcpu);
> -- 
> 2.14.2
> 

nit: not strictly necessary, but would it be worth adding a similar
(and trivial) version of this predicate to the 32bit code? Just to
keep things in sync?

Otherwise,

Acked-by: Marc Zyngier <marc.zyngier@arm.com>

	M.

-- 
Jazz is not dead, it just smell funny.