Re: [PATCH 6/6] KVM: arm64: Upgrade PMU support to ARMv8.4

Auger Eric
2021-01-15T14:03:03Z

Hi Marc,

On 1/14/21 11:56 AM, Marc Zyngier wrote:
> Upgrading the PMU code from ARMv8.1 to ARMv8.4 turns out to be
> pretty easy. All that is required is support for PMMIR_EL1, which
> is read-only, and for which returning 0 is a valid option.
>
> Let's just do that and adjust what we return to the guest.
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
> arch/arm64/kvm/sys_regs.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 8f79ec1fffa7..2f4ecbd2abfb 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1051,10 +1051,10 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
> /* Limit debug to ARMv8.0 */
> val &= ~FEATURE(ID_AA64DFR0_DEBUGVER);
> val |= FIELD_PREP(FEATURE(ID_AA64DFR0_DEBUGVER), 6);
> - /* Limit guests to PMUv3 for ARMv8.1 */
> + /* Limit guests to PMUv3 for ARMv8.4 */
> val = cpuid_feature_cap_perfmon_field(val,
> ID_AA64DFR0_PMUVER_SHIFT,
> - kvm_vcpu_has_pmu(vcpu) ? ID_AA64DFR0_PMUVER_8_1 : 0);
> + kvm_vcpu_has_pmu(vcpu) ? ID_AA64DFR0_PMUVER_8_4 : 0);
> break;
> case SYS_ID_DFR0_EL1:
> /* Limit guests to PMUv3 for ARMv8.1 */
what about the debug version in aarch32 state. Is it on purpose that you
leave it as 8_1?

Thanks

Eric
> @@ -1496,6 +1496,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>
> { SYS_DESC(SYS_PMINTENSET_EL1), access_pminten, reset_unknown, PMINTENSET_EL1 },
> { SYS_DESC(SYS_PMINTENCLR_EL1), access_pminten, reset_unknown, PMINTENSET_EL1 },
> + { SYS_DESC(SYS_PMMIR_EL1), trap_raz_wi },
>
> { SYS_DESC(SYS_MAIR_EL1), access_vm_reg, reset_unknown, MAIR_EL1 },
> { SYS_DESC(SYS_AMAIR_EL1), access_vm_reg, reset_amair_el1, AMAIR_EL1 },
>