Re: [PATCH v4 1/2] LoongArch: KVM: Add steal time support in kvm side

From: Huacai Chen
Date: Mon Jul 08 2024 - 05:47:57 EST

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On Mon, Jul 8, 2024 at 9:16 AM maobibo <maobibo@xxxxxxxxxxx> wrote:
>
>
>
> On 2024/7/6 下午5:41, Huacai Chen wrote:
> > On Sat, Jul 6, 2024 at 2:59 PM maobibo <maobibo@xxxxxxxxxxx> wrote:
> >>
> >> Huacai,
> >>
> >> On 2024/7/6 上午11:00, Huacai Chen wrote:
> >>> Hi, Bibo,
> >>>
> >>> On Fri, May 24, 2024 at 3:38 PM Bibo Mao <maobibo@xxxxxxxxxxx> wrote:
> >>>>
> >>>> Steal time feature is added here in kvm side, VM can search supported
> >>>> features provided by KVM hypervisor, feature KVM_FEATURE_STEAL_TIME
> >>>> is added here. Like x86, steal time structure is saved in guest memory,
> >>>> one hypercall function KVM_HCALL_FUNC_NOTIFY is added to notify KVM to
> >>>> enable the feature.
> >>>>
> >>>> One cpu attr ioctl command KVM_LOONGARCH_VCPU_PVTIME_CTRL is added to
> >>>> save and restore base address of steal time structure when VM is migrated.
> >>>>
> >>>> Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
> >>>> ---
> >>>> arch/loongarch/include/asm/kvm_host.h | 7 ++
> >>>> arch/loongarch/include/asm/kvm_para.h | 10 ++
> >>>> arch/loongarch/include/asm/kvm_vcpu.h | 4 +
> >>>> arch/loongarch/include/asm/loongarch.h | 1 +
> >>>> arch/loongarch/include/uapi/asm/kvm.h | 4 +
> >>>> arch/loongarch/kvm/Kconfig | 1 +
> >>>> arch/loongarch/kvm/exit.c | 38 +++++++-
> >>>> arch/loongarch/kvm/vcpu.c | 124 +++++++++++++++++++++++++
> >>>> 8 files changed, 187 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
> >>>> index c87b6ea0ec47..2eb2f7572023 100644
> >>>> --- a/arch/loongarch/include/asm/kvm_host.h
> >>>> +++ b/arch/loongarch/include/asm/kvm_host.h
> >>>> @@ -30,6 +30,7 @@
> >>>> #define KVM_PRIVATE_MEM_SLOTS 0
> >>>>
> >>>> #define KVM_HALT_POLL_NS_DEFAULT 500000
> >>>> +#define KVM_REQ_STEAL_UPDATE KVM_ARCH_REQ(1)
> >>>>
> >>>> #define KVM_GUESTDBG_SW_BP_MASK \
> >>>> (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)
> >>>> @@ -201,6 +202,12 @@ struct kvm_vcpu_arch {
> >>>> struct kvm_mp_state mp_state;
> >>>> /* cpucfg */
> >>>> u32 cpucfg[KVM_MAX_CPUCFG_REGS];
> >>>> + /* paravirt steal time */
> >>>> + struct {
> >>>> + u64 guest_addr;
> >>>> + u64 last_steal;
> >>>> + struct gfn_to_hva_cache cache;
> >>>> + } st;
> >>>> };
> >>>>
> >>>> static inline unsigned long readl_sw_gcsr(struct loongarch_csrs *csr, int reg)
> >>>> diff --git a/arch/loongarch/include/asm/kvm_para.h b/arch/loongarch/include/asm/kvm_para.h
> >>>> index 4ba2312e5f8c..a9ba8185d4af 100644
> >>>> --- a/arch/loongarch/include/asm/kvm_para.h
> >>>> +++ b/arch/loongarch/include/asm/kvm_para.h
> >>>> @@ -14,6 +14,7 @@
> >>>>
> >>>> #define KVM_HCALL_SERVICE HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_SERVICE)
> >>>> #define KVM_HCALL_FUNC_IPI 1
> >>>> +#define KVM_HCALL_FUNC_NOTIFY 2
> >>>>
> >>>> #define KVM_HCALL_SWDBG HYPERCALL_ENCODE(HYPERVISOR_KVM, KVM_HCALL_CODE_SWDBG)
> >>>>
> >>>> @@ -24,6 +25,15 @@
> >>>> #define KVM_HCALL_INVALID_CODE -1UL
> >>>> #define KVM_HCALL_INVALID_PARAMETER -2UL
> >>>>
> >>>> +#define KVM_STEAL_PHYS_VALID BIT_ULL(0)
> >>>> +#define KVM_STEAL_PHYS_MASK GENMASK_ULL(63, 6)
> >>>> +struct kvm_steal_time {
> >>>> + __u64 steal;
> >>>> + __u32 version;
> >>>> + __u32 flags;
> >>> I found that x86 has a preempted field here, in our internal repo the
> >>> LoongArch version also has this field. Moreover,
> >>> kvm_steal_time_set_preempted() and kvm_steal_time_clear_preempted()
> >>> seems needed.
> >> By my understanding, macro vcpu_is_preempted() is used together with pv
> >> spinlock, and pv spinlock depends on pv stealtime. So I think preempted
> >> flag is not part of pv stealtime, it is part of pv spinlock.
> >>
> >> We are going to add preempted field if pv spinlock is added.
> >>>
> >>>> + __u32 pad[12];
> >>>> +};
> >>>> +
> >>>> /*
> >>>> * Hypercall interface for KVM hypervisor
> >>>> *
> >>>> diff --git a/arch/loongarch/include/asm/kvm_vcpu.h b/arch/loongarch/include/asm/kvm_vcpu.h
> >>>> index 590a92cb5416..d7e51300a89f 100644
> >>>> --- a/arch/loongarch/include/asm/kvm_vcpu.h
> >>>> +++ b/arch/loongarch/include/asm/kvm_vcpu.h
> >>>> @@ -120,4 +120,8 @@ static inline void kvm_write_reg(struct kvm_vcpu *vcpu, int num, unsigned long v
> >>>> vcpu->arch.gprs[num] = val;
> >>>> }
> >>>>
> >>>> +static inline bool kvm_pvtime_supported(void)
> >>>> +{
> >>>> + return !!sched_info_on();
> >>>> +}
> >>>> #endif /* __ASM_LOONGARCH_KVM_VCPU_H__ */
> >>>> diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
> >>>> index eb09adda54b7..7a4633ef284b 100644
> >>>> --- a/arch/loongarch/include/asm/loongarch.h
> >>>> +++ b/arch/loongarch/include/asm/loongarch.h
> >>>> @@ -169,6 +169,7 @@
> >>>> #define KVM_SIGNATURE "KVM\0"
> >>>> #define CPUCFG_KVM_FEATURE (CPUCFG_KVM_BASE + 4)
> >>>> #define KVM_FEATURE_IPI BIT(1)
> >>>> +#define KVM_FEATURE_STEAL_TIME BIT(2)
> >>>>
> >>>> #ifndef __ASSEMBLY__
> >>>>
> >>>> diff --git a/arch/loongarch/include/uapi/asm/kvm.h b/arch/loongarch/include/uapi/asm/kvm.h
> >>>> index f9abef382317..ddc5cab0ffd0 100644
> >>>> --- a/arch/loongarch/include/uapi/asm/kvm.h
> >>>> +++ b/arch/loongarch/include/uapi/asm/kvm.h
> >>>> @@ -81,7 +81,11 @@ struct kvm_fpu {
> >>>> #define LOONGARCH_REG_64(TYPE, REG) (TYPE | KVM_REG_SIZE_U64 | (REG << LOONGARCH_REG_SHIFT))
> >>>> #define KVM_IOC_CSRID(REG) LOONGARCH_REG_64(KVM_REG_LOONGARCH_CSR, REG)
> >>>> #define KVM_IOC_CPUCFG(REG) LOONGARCH_REG_64(KVM_REG_LOONGARCH_CPUCFG, REG)
> >>>> +
> >>>> +/* Device Control API on vcpu fd */
> >>>> #define KVM_LOONGARCH_VCPU_CPUCFG 0
> >>>> +#define KVM_LOONGARCH_VCPU_PVTIME_CTRL 1
> >>>> +#define KVM_LOONGARCH_VCPU_PVTIME_GPA 0
> >>>>
> >>>> struct kvm_debug_exit_arch {
> >>>> };
> >>>> diff --git a/arch/loongarch/kvm/Kconfig b/arch/loongarch/kvm/Kconfig
> >>>> index c4ef2b4d9797..248744b4d086 100644
> >>>> --- a/arch/loongarch/kvm/Kconfig
> >>>> +++ b/arch/loongarch/kvm/Kconfig
> >>>> @@ -29,6 +29,7 @@ config KVM
> >>>> select KVM_MMIO
> >>>> select HAVE_KVM_READONLY_MEM
> >>>> select KVM_XFER_TO_GUEST_WORK
> >>>> + select SCHED_INFO
> >>>> help
> >>>> Support hosting virtualized guest machines using
> >>>> hardware virtualization extensions. You will need
> >>>> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
> >>>> index c86e099af5ca..e2abd97fb13f 100644
> >>>> --- a/arch/loongarch/kvm/exit.c
> >>>> +++ b/arch/loongarch/kvm/exit.c
> >>>> @@ -24,7 +24,7 @@
> >>>> static int kvm_emu_cpucfg(struct kvm_vcpu *vcpu, larch_inst inst)
> >>>> {
> >>>> int rd, rj;
> >>>> - unsigned int index;
> >>>> + unsigned int index, ret;
> >>>>
> >>>> if (inst.reg2_format.opcode != cpucfg_op)
> >>>> return EMULATE_FAIL;
> >>>> @@ -50,7 +50,10 @@ static int kvm_emu_cpucfg(struct kvm_vcpu *vcpu, larch_inst inst)
> >>>> vcpu->arch.gprs[rd] = *(unsigned int *)KVM_SIGNATURE;
> >>>> break;
> >>>> case CPUCFG_KVM_FEATURE:
> >>>> - vcpu->arch.gprs[rd] = KVM_FEATURE_IPI;
> >>>> + ret = KVM_FEATURE_IPI;
> >>>> + if (sched_info_on())
> >>> What about replacing it with your helper function kvm_pvtime_supported()?
> >> Sure, will replace it with helper function kvm_pvtime_supported().
> > If you are sure this is the only issue, then needn't submit a new version.
> OK, thanks.
>
> By searching orginal submit of vcpu_is_preempt(), it can be located at
> https://lore.kernel.org/lkml/1477642287-24104-1-git-send-email-xinhui.pan@xxxxxxxxxxxxxxxxxx/
>
> It is separated one, only that is depends on pv-spinlock and
> pv-stealtime. And there is no capability indicator for guest kernel, it
> is enabled by default.
Series applied with some modifications here, you can double-check the
correctness.
https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson.git/log/?h=loongarch-kvm

Huacai
>
> Regards
> Bibo Mao
>
> >
> > Huacai
> >
> >>
> >> Regards
> >> Bibo Mao
> >>>
> >>> Huacai
> >>>
> >>>> + ret |= KVM_FEATURE_STEAL_TIME;
> >>>> + vcpu->arch.gprs[rd] = ret;
> >>>> break;
> >>>> default:
> >>>> vcpu->arch.gprs[rd] = 0;
> >>>> @@ -687,6 +690,34 @@ static int kvm_handle_fpu_disabled(struct kvm_vcpu *vcpu)
> >>>> return RESUME_GUEST;
> >>>> }
> >>>>
> >>>> +static long kvm_save_notify(struct kvm_vcpu *vcpu)
> >>>> +{
> >>>> + unsigned long id, data;
> >>>> +
> >>>> + id = kvm_read_reg(vcpu, LOONGARCH_GPR_A1);
> >>>> + data = kvm_read_reg(vcpu, LOONGARCH_GPR_A2);
> >>>> + switch (id) {
> >>>> + case KVM_FEATURE_STEAL_TIME:
> >>>> + if (!kvm_pvtime_supported())
> >>>> + return KVM_HCALL_INVALID_CODE;
> >>>> +
> >>>> + if (data & ~(KVM_STEAL_PHYS_MASK | KVM_STEAL_PHYS_VALID))
> >>>> + return KVM_HCALL_INVALID_PARAMETER;
> >>>> +
> >>>> + vcpu->arch.st.guest_addr = data;
> >>>> + if (!(data & KVM_STEAL_PHYS_VALID))
> >>>> + break;
> >>>> +
> >>>> + vcpu->arch.st.last_steal = current->sched_info.run_delay;
> >>>> + kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
> >>>> + break;
> >>>> + default:
> >>>> + break;
> >>>> + };
> >>>> +
> >>>> + return 0;
> >>>> +};
> >>>> +
> >>>> /*
> >>>> * kvm_handle_lsx_disabled() - Guest used LSX while disabled in root.
> >>>> * @vcpu: Virtual CPU context.
> >>>> @@ -758,6 +789,9 @@ static void kvm_handle_service(struct kvm_vcpu *vcpu)
> >>>> kvm_send_pv_ipi(vcpu);
> >>>> ret = KVM_HCALL_SUCCESS;
> >>>> break;
> >>>> + case KVM_HCALL_FUNC_NOTIFY:
> >>>> + ret = kvm_save_notify(vcpu);
> >>>> + break;
> >>>> default:
> >>>> ret = KVM_HCALL_INVALID_CODE;
> >>>> break;
> >>>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> >>>> index 9e8030d45129..382796f1d3e6 100644
> >>>> --- a/arch/loongarch/kvm/vcpu.c
> >>>> +++ b/arch/loongarch/kvm/vcpu.c
> >>>> @@ -31,6 +31,117 @@ const struct kvm_stats_header kvm_vcpu_stats_header = {
> >>>> sizeof(kvm_vcpu_stats_desc),
> >>>> };
> >>>>
> >>>> +static void kvm_update_stolen_time(struct kvm_vcpu *vcpu)
> >>>> +{
> >>>> + struct kvm_steal_time __user *st;
> >>>> + struct gfn_to_hva_cache *ghc;
> >>>> + struct kvm_memslots *slots;
> >>>> + gpa_t gpa;
> >>>> + u64 steal;
> >>>> + u32 version;
> >>>> +
> >>>> + ghc = &vcpu->arch.st.cache;
> >>>> + gpa = vcpu->arch.st.guest_addr;
> >>>> + if (!(gpa & KVM_STEAL_PHYS_VALID))
> >>>> + return;
> >>>> +
> >>>> + gpa &= KVM_STEAL_PHYS_MASK;
> >>>> + slots = kvm_memslots(vcpu->kvm);
> >>>> + if (slots->generation != ghc->generation || gpa != ghc->gpa) {
> >>>> + if (kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, gpa,
> >>>> + sizeof(*st))) {
> >>>> + ghc->gpa = INVALID_GPA;
> >>>> + return;
> >>>> + }
> >>>> + }
> >>>> +
> >>>> + st = (struct kvm_steal_time __user *)ghc->hva;
> >>>> + unsafe_get_user(version, &st->version, out);
> >>>> + if (version & 1)
> >>>> + version += 1;
> >>>> + version += 1;
> >>>> + unsafe_put_user(version, &st->version, out);
> >>>> + smp_wmb();
> >>>> +
> >>>> + unsafe_get_user(steal, &st->steal, out);
> >>>> + steal += current->sched_info.run_delay -
> >>>> + vcpu->arch.st.last_steal;
> >>>> + vcpu->arch.st.last_steal = current->sched_info.run_delay;
> >>>> + unsafe_put_user(steal, &st->steal, out);
> >>>> +
> >>>> + smp_wmb();
> >>>> + version += 1;
> >>>> + unsafe_put_user(version, &st->version, out);
> >>>> +out:
> >>>> + mark_page_dirty_in_slot(vcpu->kvm, ghc->memslot, gpa_to_gfn(ghc->gpa));
> >>>> +}
> >>>> +
> >>>> +static int kvm_loongarch_pvtime_has_attr(struct kvm_vcpu *vcpu,
> >>>> + struct kvm_device_attr *attr)
> >>>> +{
> >>>> + if (!kvm_pvtime_supported() ||
> >>>> + attr->attr != KVM_LOONGARCH_VCPU_PVTIME_GPA)
> >>>> + return -ENXIO;
> >>>> +
> >>>> + return 0;
> >>>> +}
> >>>> +
> >>>> +static int kvm_loongarch_pvtime_get_attr(struct kvm_vcpu *vcpu,
> >>>> + struct kvm_device_attr *attr)
> >>>> +{
> >>>> + u64 __user *user = (u64 __user *)attr->addr;
> >>>> + u64 gpa;
> >>>> +
> >>>> + if (!kvm_pvtime_supported() ||
> >>>> + attr->attr != KVM_LOONGARCH_VCPU_PVTIME_GPA)
> >>>> + return -ENXIO;
> >>>> +
> >>>> + gpa = vcpu->arch.st.guest_addr;
> >>>> + if (put_user(gpa, user))
> >>>> + return -EFAULT;
> >>>> +
> >>>> + return 0;
> >>>> +}
> >>>> +
> >>>> +static int kvm_loongarch_pvtime_set_attr(struct kvm_vcpu *vcpu,
> >>>> + struct kvm_device_attr *attr)
> >>>> +{
> >>>> + u64 __user *user = (u64 __user *)attr->addr;
> >>>> + struct kvm *kvm = vcpu->kvm;
> >>>> + u64 gpa;
> >>>> + int ret = 0;
> >>>> + int idx;
> >>>> +
> >>>> + if (!kvm_pvtime_supported() ||
> >>>> + attr->attr != KVM_LOONGARCH_VCPU_PVTIME_GPA)
> >>>> + return -ENXIO;
> >>>> +
> >>>> + if (get_user(gpa, user))
> >>>> + return -EFAULT;
> >>>> +
> >>>> + if (gpa & ~(KVM_STEAL_PHYS_MASK | KVM_STEAL_PHYS_VALID))
> >>>> + return -EINVAL;
> >>>> +
> >>>> + if (!(gpa & KVM_STEAL_PHYS_VALID)) {
> >>>> + vcpu->arch.st.guest_addr = gpa;
> >>>> + return 0;
> >>>> + }
> >>>> +
> >>>> + /* Check the address is in a valid memslot */
> >>>> + idx = srcu_read_lock(&kvm->srcu);
> >>>> + if (kvm_is_error_hva(gfn_to_hva(kvm, gpa >> PAGE_SHIFT)))
> >>>> + ret = -EINVAL;
> >>>> + srcu_read_unlock(&kvm->srcu, idx);
> >>>> +
> >>>> + if (!ret) {
> >>>> + vcpu->arch.st.guest_addr = gpa;
> >>>> + vcpu->arch.st.last_steal = current->sched_info.run_delay;
> >>>> + kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
> >>>> + }
> >>>> +
> >>>> + return ret;
> >>>> +}
> >>>> +
> >>>> /*
> >>>> * kvm_check_requests - check and handle pending vCPU requests
> >>>> *
> >>>> @@ -48,6 +159,9 @@ static int kvm_check_requests(struct kvm_vcpu *vcpu)
> >>>> if (kvm_dirty_ring_check_request(vcpu))
> >>>> return RESUME_HOST;
> >>>>
> >>>> + if (kvm_check_request(KVM_REQ_STEAL_UPDATE, vcpu))
> >>>> + kvm_update_stolen_time(vcpu);
> >>>> +
> >>>> return RESUME_GUEST;
> >>>> }
> >>>>
> >>>> @@ -671,6 +785,9 @@ static int kvm_loongarch_vcpu_has_attr(struct kvm_vcpu *vcpu,
> >>>> case KVM_LOONGARCH_VCPU_CPUCFG:
> >>>> ret = kvm_loongarch_cpucfg_has_attr(vcpu, attr);
> >>>> break;
> >>>> + case KVM_LOONGARCH_VCPU_PVTIME_CTRL:
> >>>> + ret = kvm_loongarch_pvtime_has_attr(vcpu, attr);
> >>>> + break;
> >>>> default:
> >>>> break;
> >>>> }
> >>>> @@ -703,6 +820,9 @@ static int kvm_loongarch_vcpu_get_attr(struct kvm_vcpu *vcpu,
> >>>> case KVM_LOONGARCH_VCPU_CPUCFG:
> >>>> ret = kvm_loongarch_get_cpucfg_attr(vcpu, attr);
> >>>> break;
> >>>> + case KVM_LOONGARCH_VCPU_PVTIME_CTRL:
> >>>> + ret = kvm_loongarch_pvtime_get_attr(vcpu, attr);
> >>>> + break;
> >>>> default:
> >>>> break;
> >>>> }
> >>>> @@ -725,6 +845,9 @@ static int kvm_loongarch_vcpu_set_attr(struct kvm_vcpu *vcpu,
> >>>> case KVM_LOONGARCH_VCPU_CPUCFG:
> >>>> ret = kvm_loongarch_cpucfg_set_attr(vcpu, attr);
> >>>> break;
> >>>> + case KVM_LOONGARCH_VCPU_PVTIME_CTRL:
> >>>> + ret = kvm_loongarch_pvtime_set_attr(vcpu, attr);
> >>>> + break;
> >>>> default:
> >>>> break;
> >>>> }
> >>>> @@ -1084,6 +1207,7 @@ 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);
> >>>> + kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
> >>>>
> >>>> /* Don't bother restoring registers multiple times unless necessary */
> >>>> if (vcpu->arch.aux_inuse & KVM_LARCH_HWCSR_USABLE)
> >>>> --
> >>>> 2.39.3
> >>>>
> >>
>
>

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