| Message ID | 20230302055033.3081456-2-reijiw@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: arm64: PMU: Preserve vPMC registers properly on migration | expand |
On Thu, 02 Mar 2023 05:50:32 +0000, Reiji Watanabe <reijiw@google.com> 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@google.com> > --- > 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@kernel.org> M.
Hi Marc, On Sun, Mar 12, 2023 at 7:57 AM Marc Zyngier <maz@kernel.org> wrote: > > On Thu, 02 Mar 2023 05:50:32 +0000, > Reiji Watanabe <reijiw@google.com> 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@google.com> > > --- > > 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. Yes, exactly. > > > +} > > + > > 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@kernel.org> Thank you! Reiji > > M. > > -- > Without deviation from the norm, progress is not possible.
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; +} + 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),
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@google.com> --- arch/arm64/kvm/sys_regs.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)