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

From: Christoffer Dall <christoffer.dall@linaro.org>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: Andrew Jones <drjones@redhat.com>,
	kvm@vger.kernel.org, Tomasz Nowicki <tn@semihalf.com>,
	kvmarm@lists.cs.columbia.edu, Julien Grall <julien.grall@arm.com>,
	Yury Norov <ynorov@caviumnetworks.com>,
	linux-arm-kernel@lists.infradead.org,
	Dave Martin <Dave.Martin@arm.com>,
	Shih-Wei Li <shihwei@cs.columbia.edu>
Subject: Re: [PATCH v4 08/40] KVM: arm/arm64: Introduce vcpu_el1_is_32bit
Date: Thu, 22 Feb 2018 10:11:39 +0100	[thread overview]
Message-ID: <20180222091139.GE29376@cbox> (raw)
In-Reply-To: <86d10ylf94.wl-marc.zyngier@arm.com>

On Wed, Feb 21, 2018 at 12:05:27PM +0000, Marc Zyngier wrote:
> 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?
> 

I could, but wouldn't that add unused code to the kernel at no immediate
benefit?

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

Thanks,
-Christoffer