Messages in this thread |  | | Subject | Re: [PATCH 4/6] x86/kvm: introduce per cpu vcpu masks | From | Paolo Bonzini <> | Date | Mon, 26 Jul 2021 15:32:01 +0200 |
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On 01/07/21 17:41, Juergen Gross wrote: > In order to support high vcpu numbers per guest don't use on stack > vcpu bitmasks. As all those currently used bitmasks are not used in > functions subject to recursion it is fairly easy to replace them with > percpu bitmasks. > > Disable preemption while such a bitmask is being used in order to > avoid double usage in case we'd switch cpus. > > Signed-off-by: Juergen Gross <jgross@suse.com>
Please use a local_lock instead of disabling preemption.
Paolo
> --- > arch/x86/include/asm/kvm_host.h | 7 +++++++ > arch/x86/kvm/hyperv.c | 25 ++++++++++++++++++------- > arch/x86/kvm/irq_comm.c | 9 +++++++-- > arch/x86/kvm/x86.c | 20 +++++++++++++++++++- > 4 files changed, 51 insertions(+), 10 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 88b1ff898fb9..79138c91f83d 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1514,6 +1514,13 @@ extern u64 kvm_default_tsc_scaling_ratio; > extern bool kvm_has_bus_lock_exit; > /* maximum vcpu-id */ > extern unsigned int max_vcpu_id; > +/* per cpu vcpu bitmasks (disable preemption during usage) */ > +extern unsigned long __percpu *kvm_pcpu_vcpu_mask; > +#define KVM_VCPU_MASK_SZ \ > + (sizeof(*kvm_pcpu_vcpu_mask) * BITS_TO_LONGS(KVM_MAX_VCPUS)) > +extern u64 __percpu *kvm_hv_vp_bitmap; > +#define KVM_HV_MAX_SPARSE_VCPU_SET_BITS DIV_ROUND_UP(KVM_MAX_VCPUS, 64) > +#define KVM_HV_VPMAP_SZ (sizeof(u64) * KVM_HV_MAX_SPARSE_VCPU_SET_BITS) > > extern u64 kvm_mce_cap_supported; > > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c > index f00830e5202f..32d31a7334fa 100644 > --- a/arch/x86/kvm/hyperv.c > +++ b/arch/x86/kvm/hyperv.c > @@ -40,7 +40,7 @@ > /* "Hv#1" signature */ > #define HYPERV_CPUID_SIGNATURE_EAX 0x31237648 > > -#define KVM_HV_MAX_SPARSE_VCPU_SET_BITS DIV_ROUND_UP(KVM_MAX_VCPUS, 64) > +u64 __percpu *kvm_hv_vp_bitmap; > > static void stimer_mark_pending(struct kvm_vcpu_hv_stimer *stimer, > bool vcpu_kick); > @@ -1612,8 +1612,7 @@ static __always_inline unsigned long *sparse_set_to_vcpu_mask( > struct kvm_vcpu *vcpu; > int i, bank, sbank = 0; > > - memset(vp_bitmap, 0, > - KVM_HV_MAX_SPARSE_VCPU_SET_BITS * sizeof(*vp_bitmap)); > + memset(vp_bitmap, 0, KVM_HV_VPMAP_SZ); > for_each_set_bit(bank, (unsigned long *)&valid_bank_mask, > KVM_HV_MAX_SPARSE_VCPU_SET_BITS) > vp_bitmap[bank] = sparse_banks[sbank++]; > @@ -1637,8 +1636,8 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, u64 ingpa, u16 rep_cnt, bool > struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); > struct hv_tlb_flush_ex flush_ex; > struct hv_tlb_flush flush; > - u64 vp_bitmap[KVM_HV_MAX_SPARSE_VCPU_SET_BITS]; > - DECLARE_BITMAP(vcpu_bitmap, KVM_MAX_VCPUS); > + u64 *vp_bitmap; > + unsigned long *vcpu_bitmap; > unsigned long *vcpu_mask; > u64 valid_bank_mask; > u64 sparse_banks[64]; > @@ -1696,6 +1695,10 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, u64 ingpa, u16 rep_cnt, bool > > cpumask_clear(&hv_vcpu->tlb_flush); > > + preempt_disable(); > + vcpu_bitmap = this_cpu_ptr(kvm_pcpu_vcpu_mask); > + vp_bitmap = this_cpu_ptr(kvm_hv_vp_bitmap); > + > vcpu_mask = all_cpus ? NULL : > sparse_set_to_vcpu_mask(kvm, sparse_banks, valid_bank_mask, > vp_bitmap, vcpu_bitmap); > @@ -1707,6 +1710,8 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, u64 ingpa, u16 rep_cnt, bool > kvm_make_vcpus_request_mask(kvm, KVM_REQ_HV_TLB_FLUSH, > NULL, vcpu_mask, &hv_vcpu->tlb_flush); > > + preempt_enable(); > + > ret_success: > /* We always do full TLB flush, set rep_done = rep_cnt. */ > return (u64)HV_STATUS_SUCCESS | > @@ -1738,8 +1743,8 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, u64 ingpa, u64 outgpa, > struct kvm *kvm = vcpu->kvm; > struct hv_send_ipi_ex send_ipi_ex; > struct hv_send_ipi send_ipi; > - u64 vp_bitmap[KVM_HV_MAX_SPARSE_VCPU_SET_BITS]; > - DECLARE_BITMAP(vcpu_bitmap, KVM_MAX_VCPUS); > + u64 *vp_bitmap; > + unsigned long *vcpu_bitmap; > unsigned long *vcpu_mask; > unsigned long valid_bank_mask; > u64 sparse_banks[64]; > @@ -1796,12 +1801,18 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, u64 ingpa, u64 outgpa, > if ((vector < HV_IPI_LOW_VECTOR) || (vector > HV_IPI_HIGH_VECTOR)) > return HV_STATUS_INVALID_HYPERCALL_INPUT; > > + preempt_disable(); > + vcpu_bitmap = this_cpu_ptr(kvm_pcpu_vcpu_mask); > + vp_bitmap = this_cpu_ptr(kvm_hv_vp_bitmap); > + > vcpu_mask = all_cpus ? NULL : > sparse_set_to_vcpu_mask(kvm, sparse_banks, valid_bank_mask, > vp_bitmap, vcpu_bitmap); > > kvm_send_ipi_to_many(kvm, vector, vcpu_mask); > > + preempt_enable(); > + > ret_success: > return HV_STATUS_SUCCESS; > } > diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c > index d5b72a08e566..be4424ddcd8f 100644 > --- a/arch/x86/kvm/irq_comm.c > +++ b/arch/x86/kvm/irq_comm.c > @@ -47,7 +47,7 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src, > { > int i, r = -1; > struct kvm_vcpu *vcpu, *lowest = NULL; > - unsigned long dest_vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)]; > + unsigned long *dest_vcpu_bitmap; > unsigned int dest_vcpus = 0; > > if (kvm_irq_delivery_to_apic_fast(kvm, src, irq, &r, dest_map)) > @@ -59,7 +59,10 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src, > irq->delivery_mode = APIC_DM_FIXED; > } > > - memset(dest_vcpu_bitmap, 0, sizeof(dest_vcpu_bitmap)); > + preempt_disable(); > + dest_vcpu_bitmap = this_cpu_ptr(kvm_pcpu_vcpu_mask); > + > + memset(dest_vcpu_bitmap, 0, KVM_VCPU_MASK_SZ); > > kvm_for_each_vcpu(i, vcpu, kvm) { > if (!kvm_apic_present(vcpu)) > @@ -93,6 +96,8 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src, > lowest = kvm_get_vcpu(kvm, idx); > } > > + preempt_enable(); > + > if (lowest) > r = kvm_apic_set_irq(lowest, irq, dest_map); > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 0390d90fd360..3af398ef1fc9 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -180,6 +180,8 @@ module_param(pi_inject_timer, bint, S_IRUGO | S_IWUSR); > unsigned int __read_mostly max_vcpu_id = KVM_DEFAULT_MAX_VCPU_ID; > module_param(max_vcpu_id, uint, S_IRUGO); > > +unsigned long __percpu *kvm_pcpu_vcpu_mask; > + > /* > * Restoring the host value for MSRs that are only consumed when running in > * usermode, e.g. SYSCALL MSRs and TSC_AUX, can be deferred until the CPU > @@ -10646,9 +10648,18 @@ int kvm_arch_hardware_setup(void *opaque) > if (boot_cpu_has(X86_FEATURE_XSAVES)) > rdmsrl(MSR_IA32_XSS, host_xss); > > + kvm_pcpu_vcpu_mask = __alloc_percpu(KVM_VCPU_MASK_SZ, > + sizeof(unsigned long)); > + kvm_hv_vp_bitmap = __alloc_percpu(KVM_HV_VPMAP_SZ, sizeof(u64)); > + > + if (!kvm_pcpu_vcpu_mask || !kvm_hv_vp_bitmap) { > + r = -ENOMEM; > + goto err; > + } > + > r = ops->hardware_setup(); > if (r != 0) > - return r; > + goto err; > > memcpy(&kvm_x86_ops, ops->runtime_ops, sizeof(kvm_x86_ops)); > kvm_ops_static_call_update(); > @@ -10676,11 +10687,18 @@ int kvm_arch_hardware_setup(void *opaque) > > kvm_init_msr_list(); > return 0; > + > + err: > + free_percpu(kvm_pcpu_vcpu_mask); > + free_percpu(kvm_hv_vp_bitmap); > + return r; > } > > void kvm_arch_hardware_unsetup(void) > { > static_call(kvm_x86_hardware_unsetup)(); > + free_percpu(kvm_pcpu_vcpu_mask); > + free_percpu(kvm_hv_vp_bitmap); > } > > int kvm_arch_check_processor_compat(void *opaque) >
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