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

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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().

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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