On Thu, 02 Mar 2023 05:50:32 +0000,
Reiji Watanabe <reijiw@xxxxxxxxxx> wrote:
>
> Have KVM_GET_ONE_REG for vPMU counter (vPMC) registers (PMCCNTR_EL0
> and PMEVCNTR<n>_EL0) return the sum of the register value in the sysreg
> file and the current perf event counter value.
>
> Values of vPMC registers are saved in sysreg files on certain occasions.
> These saved values don't represent the current values of the vPMC
> registers if the perf events for the vPMCs count events after the save.
> The current values of those registers are the sum of the sysreg file
> value and the current perf event counter value. But, when userspace
> reads those registers (using KVM_GET_ONE_REG), KVM returns the sysreg
> file value to userspace (not the sum value).
>
> Fix this to return the sum value for KVM_GET_ONE_REG.
>
> Signed-off-by: Reiji Watanabe <reijiw@xxxxxxxxxx>
> ---
> arch/arm64/kvm/sys_regs.c | 21 +++++++++++++++++++--
> 1 file changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index c6cbfe6b854b..c48c053d6146 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -765,6 +765,22 @@ static bool pmu_counter_idx_valid(struct kvm_vcpu *vcpu, u64 idx)
> return true;
> }
>
> +static int get_pmu_evcntr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
> + u64 *val)
> +{
> + u64 idx;
> +
> + if (r->CRn == 9 && r->CRm == 13 && r->Op2 == 0)
> + /* PMCCNTR_EL0 */
> + idx = ARMV8_PMU_CYCLE_IDX;
> + else
> + /* PMEVCNTRn_EL0 */
> + idx = ((r->CRm & 3) << 3) | (r->Op2 & 7);
> +
> + *val = kvm_pmu_get_counter_value(vcpu, idx);
> + return 0;
It is a bit odd not to return an error when no PMU present, but this
is already filtered out by the top-level accessors.
> +}
> +
> static bool access_pmu_evcntr(struct kvm_vcpu *vcpu,
> struct sys_reg_params *p,
> const struct sys_reg_desc *r)
> @@ -981,7 +997,7 @@ static bool access_pmuserenr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
> /* Macro to expand the PMEVCNTRn_EL0 register */
> #define PMU_PMEVCNTR_EL0(n) \
> { PMU_SYS_REG(SYS_PMEVCNTRn_EL0(n)), \
> - .reset = reset_pmevcntr, \
> + .reset = reset_pmevcntr, .get_user = get_pmu_evcntr, \
> .access = access_pmu_evcntr, .reg = (PMEVCNTR0_EL0 + n), }
>
> /* Macro to expand the PMEVTYPERn_EL0 register */
> @@ -1745,7 +1761,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
> { PMU_SYS_REG(SYS_PMCEID1_EL0),
> .access = access_pmceid, .reset = NULL },
> { PMU_SYS_REG(SYS_PMCCNTR_EL0),
> - .access = access_pmu_evcntr, .reset = reset_unknown, .reg = PMCCNTR_EL0 },
> + .access = access_pmu_evcntr, .reset = reset_unknown,
> + .reg = PMCCNTR_EL0, .get_user = get_pmu_evcntr},
> { PMU_SYS_REG(SYS_PMXEVTYPER_EL0),
> .access = access_pmu_evtyper, .reset = NULL },
> { PMU_SYS_REG(SYS_PMXEVCNTR_EL0),
Reviewed-by: Marc Zyngier <maz@xxxxxxxxxx>
M.
--
Without deviation from the norm, progress is not possible.
