Re: [PATCH v3 2/6] KVM: arm64: maintain per VM value for CTR_EL0

[Sebastian Ott]

Hej Eric,

On Wed, 29 May 2024, Eric Auger wrote:
> >  static int set_clidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
> >  		      u64 val)
> >  {
> > -	u64 ctr_el0 = read_sanitised_ftr_reg(SYS_CTR_EL0);
> >  	u64 idc = !CLIDR_LOC(val) || (!CLIDR_LOUIS(val) && !CLIDR_LOUU(val));
> > +	u64 ctr_el0 = vcpu->kvm->arch.ctr_el0;
> >
> >  	if ((val & CLIDR_EL1_RES0) || (!(ctr_el0 & CTR_EL0_IDC) && idc))
> >  		return -EINVAL;
> nit: you may update the function doc comment which the extra handling of
> CTR_EL0.

Hm, there's no extra handling of CTR_EL0 it just uses the emulated value.

> > @@ -3557,6 +3557,13 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu)
> >  	struct kvm *kvm = vcpu->kvm;
> >  	unsigned long i;
> >
> > +	if (!kvm_vcpu_initialized(vcpu))
> at this stage of the reading, why is the above check needed?

To make sure that a later call to this function doesn't overwrite
the value provided by userspace. (See e016333745c "KVM: arm64: Only
reset vCPU-scoped feature ID regs once").

Sebastian