Subject: [PATCH v7 15/19] KVM: ARM64: Add access handler for PMUSERENR register

From: [email-masked] (Shannon Zhao)
Date: Tue, 15 Dec 2015 23:59:08 +0800

On 2015/12/15 22:58, Marc Zyngier wrote:
> On 15/12/15 08:49, Shannon Zhao wrote:
>> >From: Shannon Zhao<[email-masked]>
>> >
>> >The reset value of PMUSERENR_EL0 is UNKNOWN, use reset_unknown.
>> >
>> >PMUSERENR_EL0 holds some bits which decide whether PMU registers can be
>> >accessed from EL0. Add some check helpers to handle the access from EL0.
>> >
>> >Signed-off-by: Shannon Zhao<[email-masked]>
>> >---
>> >  arch/arm64/kvm/sys_regs.c | 124 ++++++++++++++++++++++++++++++++++++++++++++--
>> >  1 file changed, 119 insertions(+), 5 deletions(-)
>> >
>> >diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> >index b2ccc25..bad3dfd 100644
>> >--- a/arch/arm64/kvm/sys_regs.c
>> >+++ b/arch/arm64/kvm/sys_regs.c
>> >@@ -452,12 +452,44 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
>> >  	vcpu_sys_reg(vcpu, r->reg) = val;
>> >  }
>> >
>> >+static inline bool pmu_access_el0_disabled(struct kvm_vcpu *vcpu)
>> >+{
>> >+	u64 reg = vcpu_sys_reg(vcpu, PMUSERENR_EL0);
>> >+
>> >+	return !((reg & 0x1) || vcpu_mode_priv(vcpu));
>> >+}
>> >+
>> >+static inline bool pmu_write_swinc_el0_disabled(struct kvm_vcpu *vcpu)
>> >+{
>> >+	u64 reg = vcpu_sys_reg(vcpu, PMUSERENR_EL0);
>> >+
>> >+	return !((reg & 0x3) || vcpu_mode_priv(vcpu));
>> >+}
>> >+
>> >+static inline bool pmu_access_cycle_counter_el0_disabled(struct kvm_vcpu *vcpu)
>> >+{
>> >+	u64 reg = vcpu_sys_reg(vcpu, PMUSERENR_EL0);
>> >+
>> >+	return !((reg & 0x5) || vcpu_mode_priv(vcpu));
>> >+}
>> >+
>> >+static inline bool pmu_access_event_counter_el0_disabled(struct kvm_vcpu *vcpu)
>> >+{
>> >+	u64 reg = vcpu_sys_reg(vcpu, PMUSERENR_EL0);
>> >+
>> >+	return !((reg & 0x9) || vcpu_mode_priv(vcpu));
>> >+}
> Please add #defines for the PMUSERNR_EL0 bits.
>
>> >+
>> >  static bool access_pmcr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>> >  			const struct sys_reg_desc *r)
>> >  {
>> >  	u64 val;
>> >+	bool unaccessible = pmu_access_el0_disabled(vcpu);
>> >
>> >  	if (p->is_write) {
>> >+		if (unaccessible)
>> >+			return ignore_write(vcpu, p);
>> >+
> This is not how this is supposed to work. If EL0 is denied access to the
> PMU, you must inject an exception into EL1 for it to handle the fault.
> The code should reflect the flow described at D5.11.2 in the ARM ARM.
>
Does it need to add a helper to inject an exception into EL1 or is there 
a existing one?

Thanks,
-- 
Shannon