Subject: [PATCH v4 31/40] KVM: arm64: Move common VHE/non-VHE trap config in separate functions

From: [email-masked] (Christoffer Dall)
Date: Thu, 22 Feb 2018 19:17:19 +0100

On Wed, Feb 21, 2018 at 05:59:37PM +0000, Marc Zyngier wrote:
> On Thu, 15 Feb 2018 21:03:23 +0000,
> Christoffer Dall wrote:
> > 
> > As we are about to be more lazy with some of the trap configuration
> > register read/writes for VHE systems, move the logic that is currently
> > shared between VHE and non-VHE into a separate function which can be
> > called from either the world-switch path or from vcpu_load/vcpu_put.
> > 
> > Signed-off-by: Christoffer Dall <[email-masked]>
> > ---
> > 
> > Notes:
> >     Changes since v3:
> >      - Separate fpsimd32 trap configuration into a separate function
> >        which is still called from __activate_traps, because we no longer
> >        defer saving/restoring of VFP registers to load/put.
> > 
> >  arch/arm64/kvm/hyp/switch.c | 76 +++++++++++++++++++++++++++------------------
> >  1 file changed, 45 insertions(+), 31 deletions(-)
> > 
> > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> > index 909aa3fe9196..17e3c6f26a34 100644
> > --- a/arch/arm64/kvm/hyp/switch.c
> > +++ b/arch/arm64/kvm/hyp/switch.c
> > @@ -56,7 +56,45 @@ static inline void __hyp_text __fpsimd_save_fpexc32(struct kvm_vcpu *vcpu)
> >  	vcpu->arch.ctxt.sys_regs[FPEXC32_EL2] = read_sysreg(fpexc32_el2);
> >  }
> >  
> > -static void __hyp_text __activate_traps_vhe(void)
> > +static void __hyp_text __activate_traps_fpsimd32(struct kvm_vcpu *vcpu)
> > +{
> > +	/*
> > +	 * We are about to set CPTR_EL2.TFP to trap all floating point
> > +	 * register accesses to EL2, however, the ARM ARM clearly states that
> > +	 * traps are only taken to EL2 if the operation would not otherwise
> > +	 * trap to EL1.  Therefore, always make sure that for 32-bit guests,
> > +	 * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
> > +	 * If FP/ASIMD is not implemented, FPEXC is UNDEFINED and any access to
> > +	 * it will cause an exception.
> > +	 */
> > +	if (vcpu_el1_is_32bit(vcpu) && system_supports_fpsimd()) {
> > +		write_sysreg(1 << 30, fpexc32_el2);
> > +		isb();
> > +	}
> > +}
> > +
> > +static void __hyp_text __activate_traps_common(struct kvm_vcpu *vcpu)
> > +{
> > +	/* Trap on AArch32 cp15 c15 (impdef sysregs) accesses (EL1 or EL0) */
> > +	write_sysreg(1 << 15, hstr_el2);
> > +	/*
> > +	 * Make sure we trap PMU access from EL0 to EL2. Also sanitize
> > +	 * PMSELR_EL0 to make sure it never contains the cycle
> > +	 * counter, which could make a PMXEVCNTR_EL0 access UNDEF at
> > +	 * EL1 instead of being trapped to EL2.
> > +	 */
> > +	write_sysreg(0, pmselr_el0);
> > +	write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
> > +	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
> > +}
> > +
> > +static void __hyp_text __deactivate_traps_common(void)
> > +{
> > +	write_sysreg(0, hstr_el2);
> > +	write_sysreg(0, pmuserenr_el0);
> > +}
> > +
> > +static void __hyp_text __activate_traps_vhe(struct kvm_vcpu *vcpu)
> >  {
> >  	u64 val;
> >  
> > @@ -68,7 +106,7 @@ static void __hyp_text __activate_traps_vhe(void)
> >  	write_sysreg(kvm_get_hyp_vector(), vbar_el1);
> >  }
> >  
> > -static void __hyp_text __activate_traps_nvhe(void)
> > +static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
> 
> I have the ugly feeling that this hunk should not be in this
> patch. Have you tried bisecting the compilation of this series?
> 

I have, and I seem to remember catching this one during that exact
exercise, but I probably committed the change to the wrong patch.  Duh.

Thanks for spotting.
-Christoffer

> >  {
> >  	u64 val;
> >  
> > @@ -85,37 +123,14 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
> >  {
> >  	u64 hcr = vcpu->arch.hcr_el2;
> >  
> > -	/*
> > -	 * We are about to set CPTR_EL2.TFP to trap all floating point
> > -	 * register accesses to EL2, however, the ARM ARM clearly states that
> > -	 * traps are only taken to EL2 if the operation would not otherwise
> > -	 * trap to EL1.  Therefore, always make sure that for 32-bit guests,
> > -	 * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
> > -	 * If FP/ASIMD is not implemented, FPEXC is UNDEFINED and any access to
> > -	 * it will cause an exception.
> > -	 */
> > -	if (vcpu_el1_is_32bit(vcpu) && system_supports_fpsimd()) {
> > -		write_sysreg(1 << 30, fpexc32_el2);
> > -		isb();
> > -	}
> > +	write_sysreg(hcr, hcr_el2);
> >  
> >  	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);
> > -	/*
> > -	 * Make sure we trap PMU access from EL0 to EL2. Also sanitize
> > -	 * PMSELR_EL0 to make sure it never contains the cycle
> > -	 * counter, which could make a PMXEVCNTR_EL0 access UNDEF at
> > -	 * EL1 instead of being trapped to EL2.
> > -	 */
> > -	write_sysreg(0, pmselr_el0);
> > -	write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
> > -	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
> > -	__activate_traps_arch()();
> > +	__activate_traps_fpsimd32(vcpu);
> > +	__activate_traps_common(vcpu);
> > +	__activate_traps_arch()(vcpu);
> >  }
> >  
> >  static void __hyp_text __deactivate_traps_vhe(void)
> > @@ -160,9 +175,8 @@ static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu)
> >  	if (vcpu->arch.hcr_el2 & HCR_VSE)
> >  		vcpu->arch.hcr_el2 = read_sysreg(hcr_el2);
> >  
> > +	__deactivate_traps_common();
> >  	__deactivate_traps_arch()();
> > -	write_sysreg(0, hstr_el2);
> > -	write_sysreg(0, pmuserenr_el0);
> >  }
> >  
> >  static void __hyp_text __activate_vm(struct kvm *kvm)
> > -- 
> > 2.14.2
> > 
> 
> Otherwise:
> 
> Reviewed-by: Marc Zyngier <[email-masked]>
> 
> 	M.
> 
> -- 
> Jazz is not dead, it just smell funny.