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Message-ID: <a23c22bc-5afd-34e7-a08b-8e3f9c7c9f47@loongson.cn>
Date: Wed, 24 Apr 2024 09:07:59 +0800
From: maobibo <maobibo@...ngson.cn>
To: gaosong <gaosong@...ngson.cn>, linux-kernel@...r.kernel.org
Cc: pbonzini@...hat.com, zhaotianrui@...ngson.cn, chenhuacai@...nel.org,
kernel@...0n.name, loongarch@...ts.linux.dev
Subject: Re: [PATCH v2] LoongArch: KVM: Add PMU support
On 2024/4/23 下午8:41, gaosong wrote:
> 在 2024/4/22 上午10:37, maobibo 写道:
>>
>>
>> On 2024/4/17 下午2:52, Song Gao wrote:
>>> On LoongArch, the host and guest have their own PMU CSRs registers
>>> and they share PMU hardware resources. A set of PMU CSRs consists of
>>> a CTRL register and a CNTR register. We can set which PMU CSRs are used
>>> by the guest by writing to the GCFG register [24: 26] bits.
>> There are some problems with this method.
>> 1. perf core also register task switch callback, the function name is
>> perf_event_task_sched_in() , and it is called before kvm task switch
>> callback fire_sched_in_preempt_notifiers().
>>
>> 2. perf core will access pmu hw in tick timer/hrtimer/ipi function call,
>> such as function perf_event_task_tick() is called in tick timer, there
>> are event_function_call(event, __perf_event_xxx, &value) in file
>> kernel/events/core.c.
>>
> How about putting kvm_lose_pmu() in kvm_handler_exit()?
> That would avoid these problems.
That is ok for me, we can improve in later.
Regards
Bibo Mao
>
> Thanks.
> Song Gao
>> Maybe there need some modifications with perf core.
>>
>> Regards
>> Bibo Mao
>>
>>>
>>> On KVM side. we save the host PMU CSRs into structure kvm_context.
>>> If the host supports the PMU feature. When entering guest mode.
>>> we save the host PMU CSRs and restore the guest PMU CSRs. When exiting
>>> guest mode, we save the guest PMU CSRs and restore the host PMU CSRs.
>>>
>>> Signed-off-by: Song Gao <gaosong@...ngson.cn>
>>>
>>> v1->v2:
>>> 1. Add new vcpu->request flag KVM_REQ_PMU. If we use PMU,
>>> We need to set this flag;
>>> 2. Add kvm_check_pmu() to kvm_pre_enter_guest();
>>> 3. On _kvm_setcsr(), after modifying the PMU CSR register value,
>>> if we use PMU, we need to set KVM_REQ_PMU.
>>>
>>> ---
>>> arch/loongarch/include/asm/kvm_csr.h | 5 +
>>> arch/loongarch/include/asm/kvm_host.h | 20 +++
>>> arch/loongarch/include/asm/loongarch.h | 1 +
>>> arch/loongarch/kvm/exit.c | 8 ++
>>> arch/loongarch/kvm/vcpu.c | 185 ++++++++++++++++++++++++-
>>> 5 files changed, 217 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/loongarch/include/asm/kvm_csr.h
>>> b/arch/loongarch/include/asm/kvm_csr.h
>>> index 724ca8b7b401..289c3671ee25 100644
>>> --- a/arch/loongarch/include/asm/kvm_csr.h
>>> +++ b/arch/loongarch/include/asm/kvm_csr.h
>>> @@ -208,4 +208,9 @@ static __always_inline void
>>> kvm_change_sw_gcsr(struct loongarch_csrs *csr,
>>> csr->csrs[gid] |= val & _mask;
>>> }
>>> +#define KVM_PMU_EVENT_ENABLED (CSR_PERFCTRL_PLV0 | \
>>> + CSR_PERFCTRL_PLV1 | \
>>> + CSR_PERFCTRL_PLV2 | \
>>> + CSR_PERFCTRL_PLV3)
>>> +
>>> #endif /* __ASM_LOONGARCH_KVM_CSR_H__ */
>>> diff --git a/arch/loongarch/include/asm/kvm_host.h
>>> b/arch/loongarch/include/asm/kvm_host.h
>>> index 2d62f7b0d377..e1d64e26e7cb 100644
>>> --- a/arch/loongarch/include/asm/kvm_host.h
>>> +++ b/arch/loongarch/include/asm/kvm_host.h
>>> @@ -51,9 +51,14 @@ struct kvm_arch_memory_slot {
>>> unsigned long flags;
>>> };
>>> +#define KVM_REQ_PMU KVM_ARCH_REQ(0)
>>> +#define HOST_MAX_PMNUM 16
>>> struct kvm_context {
>>> unsigned long vpid_cache;
>>> struct kvm_vcpu *last_vcpu;
>>> + /* Save host pmu csr */
>>> + u64 perf_ctrl[HOST_MAX_PMNUM];
>>> + u64 perf_cntr[HOST_MAX_PMNUM];
>>> };
>>> struct kvm_world_switch {
>>> @@ -99,6 +104,8 @@ enum emulation_result {
>>> #define KVM_LARCH_LASX (0x1 << 2)
>>> #define KVM_LARCH_SWCSR_LATEST (0x1 << 3)
>>> #define KVM_LARCH_HWCSR_USABLE (0x1 << 4)
>>> +#define KVM_GUEST_PMU_ENABLE (0x1 << 5)
>>> +#define KVM_GUEST_PMU_ACTIVE (0x1 << 6)
>>> struct kvm_vcpu_arch {
>>> /*
>>> @@ -136,6 +143,9 @@ struct kvm_vcpu_arch {
>>> /* CSR state */
>>> struct loongarch_csrs *csr;
>>> + /* Guest max PMU CSR id */
>>> + int max_pmu_csrid;
>>> +
>>> /* GPR used as IO source/target */
>>> u32 io_gpr;
>>> @@ -195,6 +205,16 @@ static inline bool kvm_guest_has_lasx(struct
>>> kvm_vcpu_arch *arch)
>>> return arch->cpucfg[2] & CPUCFG2_LASX;
>>> }
>>> +static inline bool kvm_guest_has_pmu(struct kvm_vcpu_arch *arch)
>>> +{
>>> + return arch->cpucfg[LOONGARCH_CPUCFG6] & CPUCFG6_PMP;
>>> +}
>>> +
>>> +static inline int kvm_get_pmu_num(struct kvm_vcpu_arch *arch)
>>> +{
>>> + return (arch->cpucfg[LOONGARCH_CPUCFG6] & CPUCFG6_PMNUM) >>
>>> CPUCFG6_PMNUM_SHIFT;
>>> +}
>>> +
>>> /* Debug: dump vcpu state */
>>> int kvm_arch_vcpu_dump_regs(struct kvm_vcpu *vcpu);
>>> diff --git a/arch/loongarch/include/asm/loongarch.h
>>> b/arch/loongarch/include/asm/loongarch.h
>>> index 46366e783c84..644380b6ebec 100644
>>> --- a/arch/loongarch/include/asm/loongarch.h
>>> +++ b/arch/loongarch/include/asm/loongarch.h
>>> @@ -119,6 +119,7 @@
>>> #define CPUCFG6_PMP BIT(0)
>>> #define CPUCFG6_PAMVER GENMASK(3, 1)
>>> #define CPUCFG6_PMNUM GENMASK(7, 4)
>>> +#define CPUCFG6_PMNUM_SHIFT 4
>>> #define CPUCFG6_PMBITS GENMASK(13, 8)
>>> #define CPUCFG6_UPM BIT(14)
>>> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
>>> index ed1d89d53e2e..636cd1500135 100644
>>> --- a/arch/loongarch/kvm/exit.c
>>> +++ b/arch/loongarch/kvm/exit.c
>>> @@ -83,6 +83,14 @@ static int kvm_handle_csr(struct kvm_vcpu *vcpu,
>>> larch_inst inst)
>>> rj = inst.reg2csr_format.rj;
>>> csrid = inst.reg2csr_format.csr;
>>> + if (csrid >= LOONGARCH_CSR_PERFCTRL0 && csrid <=
>>> vcpu->arch.max_pmu_csrid) {
>>> + if (kvm_guest_has_pmu(&vcpu->arch)) {
>>> + vcpu->arch.pc -= 4;
>>> + kvm_make_request(KVM_REQ_PMU, vcpu);
>>> + return EMULATE_DONE;
>>> + }
>>> + }
>>> +
>>> /* Process CSR ops */
>>> switch (rj) {
>>> case 0: /* process csrrd */
>>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
>>> index 3a8779065f73..daef2498ad48 100644
>>> --- a/arch/loongarch/kvm/vcpu.c
>>> +++ b/arch/loongarch/kvm/vcpu.c
>>> @@ -30,6 +30,144 @@ const struct kvm_stats_header
>>> kvm_vcpu_stats_header = {
>>> sizeof(kvm_vcpu_stats_desc),
>>> };
>>> +static inline void kvm_save_host_pmu(struct kvm_vcpu *vcpu)
>>> +{
>>> + struct kvm_context *context;
>>> +
>>> + context = this_cpu_ptr(vcpu->kvm->arch.vmcs);
>>> + context->perf_ctrl[0] = read_csr_perfctrl0();
>>> + context->perf_cntr[0] = read_csr_perfcntr0();
>>> + context->perf_ctrl[1] = read_csr_perfctrl1();
>>> + context->perf_cntr[1] = read_csr_perfcntr1();
>>> + context->perf_ctrl[2] = read_csr_perfctrl2();
>>> + context->perf_cntr[2] = read_csr_perfcntr2();
>>> + context->perf_ctrl[3] = read_csr_perfctrl3();
>>> + context->perf_cntr[3] = read_csr_perfcntr3();
>>> +}
>>> +
>>> +static inline void kvm_restore_host_pmu(struct kvm_vcpu *vcpu)
>>> +{
>>> + struct kvm_context *context;
>>> +
>>> + context = this_cpu_ptr(vcpu->kvm->arch.vmcs);
>>> + write_csr_perfctrl0(context->perf_ctrl[0]);
>>> + write_csr_perfcntr0(context->perf_cntr[0]);
>>> + write_csr_perfctrl1(context->perf_ctrl[1]);
>>> + write_csr_perfcntr1(context->perf_cntr[1]);
>>> + write_csr_perfctrl2(context->perf_ctrl[2]);
>>> + write_csr_perfcntr2(context->perf_cntr[2]);
>>> + write_csr_perfctrl3(context->perf_ctrl[3]);
>>> + write_csr_perfcntr3(context->perf_cntr[3]);
>>> +}
>>> +
>>> +
>>> +static inline void kvm_save_guest_pmu(struct kvm_vcpu *vcpu)
>>> +{
>>> + struct loongarch_csrs *csr = vcpu->arch.csr;
>>> +
>>> + kvm_save_hw_gcsr(csr, LOONGARCH_CSR_PERFCTRL0);
>>> + kvm_save_hw_gcsr(csr, LOONGARCH_CSR_PERFCNTR0);
>>> + kvm_save_hw_gcsr(csr, LOONGARCH_CSR_PERFCTRL1);
>>> + kvm_save_hw_gcsr(csr, LOONGARCH_CSR_PERFCNTR1);
>>> + kvm_save_hw_gcsr(csr, LOONGARCH_CSR_PERFCTRL2);
>>> + kvm_save_hw_gcsr(csr, LOONGARCH_CSR_PERFCNTR2);
>>> + kvm_save_hw_gcsr(csr, LOONGARCH_CSR_PERFCTRL3);
>>> + kvm_save_hw_gcsr(csr, LOONGARCH_CSR_PERFCNTR3);
>>> + kvm_write_hw_gcsr(LOONGARCH_CSR_PERFCTRL0, 0);
>>> + kvm_write_hw_gcsr(LOONGARCH_CSR_PERFCTRL1, 0);
>>> + kvm_write_hw_gcsr(LOONGARCH_CSR_PERFCTRL2, 0);
>>> + kvm_write_hw_gcsr(LOONGARCH_CSR_PERFCTRL3, 0);
>>> +}
>>> +
>>> +static inline void kvm_restore_guest_pmu(struct kvm_vcpu *vcpu)
>>> +{
>>> + struct loongarch_csrs *csr = vcpu->arch.csr;
>>> +
>>> + kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_PERFCTRL0);
>>> + kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_PERFCNTR0);
>>> + kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_PERFCTRL1);
>>> + kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_PERFCNTR1);
>>> + kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_PERFCTRL2);
>>> + kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_PERFCNTR2);
>>> + kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_PERFCTRL3);
>>> + kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_PERFCNTR3);
>>> +}
>>> +
>>> +static void kvm_lose_pmu(struct kvm_vcpu *vcpu)
>>> +{
>>> + unsigned long val;
>>> + struct loongarch_csrs *csr = vcpu->arch.csr;
>>> +
>>> + if (!(vcpu->arch.aux_inuse & KVM_GUEST_PMU_ENABLE))
>>> + return;
>>> + if (!(vcpu->arch.aux_inuse & KVM_GUEST_PMU_ACTIVE))
>>> + return;
>>> +
>>> + kvm_save_guest_pmu(vcpu);
>>> + /* Disable pmu access from guest */
>>> + write_csr_gcfg(read_csr_gcfg() & ~CSR_GCFG_GPERF);
>>> +
>>> + /*
>>> + * Clear KVM_GUEST_PMU_ENABLE if the guest is not using PMU CSRs
>>> + * when exiting the guest, so that the next time trap into the
>>> guest.
>>> + * we don't need to deal with PMU CSRs contexts.
>>> + */
>>> + val = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_PERFCTRL0);
>>> + val |= kvm_read_sw_gcsr(csr, LOONGARCH_CSR_PERFCTRL1);
>>> + val |= kvm_read_sw_gcsr(csr, LOONGARCH_CSR_PERFCTRL2);
>>> + val |= kvm_read_sw_gcsr(csr, LOONGARCH_CSR_PERFCTRL3);
>>> + if (!(val & KVM_PMU_EVENT_ENABLED))
>>> + vcpu->arch.aux_inuse &= ~KVM_GUEST_PMU_ENABLE;
>>> + kvm_restore_host_pmu(vcpu);
>>> +
>>> + /* KVM_GUEST_PMU_ACTIVE needs to be cleared when exiting the
>>> guest */
>>> + vcpu->arch.aux_inuse &= ~KVM_GUEST_PMU_ACTIVE;
>>> +}
>>> +
>>> +static void kvm_own_pmu(struct kvm_vcpu *vcpu)
>>> +{
>>> + unsigned long val;
>>> +
>>> + kvm_save_host_pmu(vcpu);
>>> + /* Set PM0-PM(num) to guest */
>>> + val = read_csr_gcfg() & ~CSR_GCFG_GPERF;
>>> + val |= (kvm_get_pmu_num(&vcpu->arch) + 1) << CSR_GCFG_GPERF_SHIFT;
>>> + write_csr_gcfg(val);
>>> + kvm_restore_guest_pmu(vcpu);
>>> +}
>>> +
>>> +static void kvm_restore_pmu(struct kvm_vcpu *vcpu)
>>> +{
>>> + if (!(vcpu->arch.aux_inuse & KVM_GUEST_PMU_ENABLE))
>>> + return;
>>> +
>>> + kvm_make_request(KVM_REQ_PMU, vcpu);
>>> +}
>>> +
>>> +static void kvm_check_pmu(struct kvm_vcpu *vcpu)
>>> +{
>>> + if (!kvm_check_request(KVM_REQ_PMU, vcpu))
>>> + return;
>>> +
>>> + kvm_own_pmu(vcpu);
>>> +
>>> + /*
>>> + * Set KVM_GUEST PMU_ENABLE and GUEST_PMU_ACTIVE
>>> + * when guest has KVM_REQ_PMU request.
>>> + */
>>> + vcpu->arch.aux_inuse |= KVM_GUEST_PMU_ENABLE;
>>> + vcpu->arch.aux_inuse |= KVM_GUEST_PMU_ACTIVE;
>>> +
>>> + /*
>>> + * Save the PMU CSRs context when there is a host PMU interrupt.
>>> + * and set KVM_REQ_PMU.
>>> + */
>>> + if (read_csr_estat() & CPU_PMU) {
>>> + kvm_lose_pmu(vcpu);
>>> + kvm_make_request(KVM_REQ_PMU, vcpu);
>>> + }
>>> +}
>>> +
>>> /*
>>> * kvm_check_requests - check and handle pending vCPU requests
>>> *
>>> @@ -100,6 +238,7 @@ static int kvm_pre_enter_guest(struct kvm_vcpu
>>> *vcpu)
>>> /* Make sure the vcpu mode has been written */
>>> smp_store_mb(vcpu->mode, IN_GUEST_MODE);
>>> kvm_check_vpid(vcpu);
>>> + kvm_check_pmu(vcpu);
>>> vcpu->arch.host_eentry = csr_read64(LOONGARCH_CSR_EENTRY);
>>> /* Clear KVM_LARCH_SWCSR_LATEST as CSR will change when
>>> enter guest */
>>> vcpu->arch.aux_inuse &= ~KVM_LARCH_SWCSR_LATEST;
>>> @@ -295,6 +434,21 @@ static int _kvm_setcsr(struct kvm_vcpu *vcpu,
>>> unsigned int id, u64 val)
>>> kvm_write_sw_gcsr(csr, id, val);
>>> + /*
>>> + * After modifying the PMU CSR register value of the vcpu.
>>> + * If the PMU CSRs are used, we need to set KVM_REQ_PMU.
>>> + */
>>> + if (id >= LOONGARCH_CSR_PERFCTRL0 && id <=
>>> LOONGARCH_CSR_PERFCNTR3) {
>>> + unsigned long val;
>>> +
>>> + val = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_PERFCTRL0);
>>> + val |= kvm_read_sw_gcsr(csr, LOONGARCH_CSR_PERFCTRL1);
>>> + val |= kvm_read_sw_gcsr(csr, LOONGARCH_CSR_PERFCTRL2);
>>> + val |= kvm_read_sw_gcsr(csr, LOONGARCH_CSR_PERFCTRL3);
>>> + if (val & KVM_PMU_EVENT_ENABLED)
>>> + kvm_make_request(KVM_REQ_PMU, vcpu);
>>> + }
>>> +
>>> return ret;
>>> }
>>> @@ -333,6 +487,12 @@ static int _kvm_get_cpucfg_mask(int id, u64 *v)
>>> case LOONGARCH_CPUCFG5:
>>> *v = GENMASK(31, 0);
>>> return 0;
>>> + case LOONGARCH_CPUCFG6:
>>> + if (cpu_has_pmp)
>>> + *v = GENMASK(14, 0);
>>> + else
>>> + *v = 0;
>>> + return 0;
>>> case LOONGARCH_CPUCFG16:
>>> *v = GENMASK(16, 0);
>>> return 0;
>>> @@ -351,7 +511,7 @@ static int _kvm_get_cpucfg_mask(int id, u64 *v)
>>> static int kvm_check_cpucfg(int id, u64 val)
>>> {
>>> - int ret;
>>> + int ret, host;
>>> u64 mask = 0;
>>> ret = _kvm_get_cpucfg_mask(id, &mask);
>>> @@ -377,6 +537,18 @@ static int kvm_check_cpucfg(int id, u64 val)
>>> /* LASX architecturally implies LSX and FP but val does
>>> not satisfy that */
>>> return -EINVAL;
>>> return 0;
>>> + case LOONGARCH_CPUCFG6:
>>> + if (val & CPUCFG6_PMP) {
>>> + host = read_cpucfg(LOONGARCH_CPUCFG6);
>>> + if ((val & CPUCFG6_PMBITS) != (host & CPUCFG6_PMBITS))
>>> + /* Guest pmbits must be the same with host */
>>> + return -EINVAL;
>>> + if ((val & CPUCFG6_PMNUM) > (host & CPUCFG6_PMNUM))
>>> + return -EINVAL;
>>> + if ((val & CPUCFG6_UPM) && !(host & CPUCFG6_UPM))
>>> + return -EINVAL;
>>> + }
>>> + return 0;
>>> default:
>>> /*
>>> * Values for the other CPUCFG IDs are not being further
>>> validated
>>> @@ -459,6 +631,10 @@ static int kvm_set_one_reg(struct kvm_vcpu *vcpu,
>>> if (ret)
>>> break;
>>> vcpu->arch.cpucfg[id] = (u32)v;
>>> + if (id == LOONGARCH_CPUCFG6) {
>>> + vcpu->arch.max_pmu_csrid = LOONGARCH_CSR_PERFCTRL0 +
>>> + 2 * kvm_get_pmu_num(&vcpu->arch) + 1;
>>> + }
>>> break;
>>> case KVM_REG_LOONGARCH_KVM:
>>> switch (reg->id) {
>>> @@ -552,7 +728,8 @@ static int kvm_loongarch_cpucfg_has_attr(struct
>>> kvm_vcpu *vcpu,
>>> struct kvm_device_attr *attr)
>>> {
>>> switch (attr->attr) {
>>> - case 2:
>>> + case LOONGARCH_CPUCFG2:
>>> + case LOONGARCH_CPUCFG6:
>>> return 0;
>>> default:
>>> return -ENXIO;
>>> @@ -982,6 +1159,9 @@ static int _kvm_vcpu_load(struct kvm_vcpu *vcpu,
>>> int cpu)
>>> /* Control guest page CCA attribute */
>>> change_csr_gcfg(CSR_GCFG_MATC_MASK, CSR_GCFG_MATC_ROOT);
>>> + /* Restore hardware PMU CSRs */
>>> + kvm_restore_pmu(vcpu);
>>> +
>>> /* Don't bother restoring registers multiple times unless
>>> necessary */
>>> if (vcpu->arch.aux_inuse & KVM_LARCH_HWCSR_USABLE)
>>> return 0;
>>> @@ -1065,6 +1245,7 @@ static int _kvm_vcpu_put(struct kvm_vcpu *vcpu,
>>> int cpu)
>>> struct loongarch_csrs *csr = vcpu->arch.csr;
>>> kvm_lose_fpu(vcpu);
>>> + kvm_lose_pmu(vcpu);
>>> /*
>>> * Update CSR state from hardware if software CSR state is stale,
>>>
>>
>
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