[PATCH v9 12/40] KVM: x86: hyper-v: Use preallocated buffer in 'struct kvm_vcpu_hv' instead of on-stack 'sparse_banks'
From: Vitaly Kuznetsov <vkuznets@redhat.com>
Date: 2022-08-03 13:45:59
Also in:
kvm, lkml
Subsystem:
kernel virtual machine for x86 (kvm/x86), kvm x86 hyper-v (kvm/hyper-v), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Vitaly Kuznetsov, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
To make kvm_hv_flush_tlb() ready to handle L2 TLB flush requests, KVM needs to allow for all 64 sparse vCPU banks regardless of KVM_MAX_VCPUs as L1 may use vCPU overcommit for L2. To avoid growing on-stack allocation, make 'sparse_banks' part of per-vCPU 'struct kvm_vcpu_hv' which is allocated dynamically. Note: sparse_set_to_vcpu_mask() can't currently be used to handle L2 requests as KVM does not keep L2 VM_ID -> L2 VCPU_ID -> L1 vCPU mappings, i.e. its vp_bitmap array is still bounded by the number of L1 vCPUs and so can remain an on-stack allocation. Reviewed-by: Maxim Levitsky <redacted> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> --- arch/x86/include/asm/kvm_host.h | 3 +++ arch/x86/kvm/hyperv.c | 6 ++++-- 2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 83c2331f7701..ca8183647b6d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h@@ -644,6 +644,9 @@ struct kvm_vcpu_hv { } cpuid_cache; struct kvm_vcpu_hv_tlb_flush_fifo tlb_flush_fifo[HV_NR_TLB_FLUSH_FIFOS]; + + /* Preallocated buffer for handling hypercalls passing sparse vCPU set */ + u64 sparse_banks[HV_MAX_SPARSE_VCPU_BANKS]; }; /* Xen HVM per vcpu emulation context */
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index d27fb4a6d94b..401649a9d288 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c@@ -1910,6 +1910,8 @@ void kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu) static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) { + struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); + u64 *sparse_banks = hv_vcpu->sparse_banks; struct kvm *kvm = vcpu->kvm; struct hv_tlb_flush_ex flush_ex; struct hv_tlb_flush flush;
@@ -1923,7 +1925,6 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) u64 __tlb_flush_entries[KVM_HV_TLB_FLUSH_FIFO_SIZE - 1]; u64 *tlb_flush_entries; u64 valid_bank_mask; - u64 sparse_banks[KVM_HV_MAX_SPARSE_VCPU_SET_BITS]; struct kvm_vcpu *v; unsigned long i; bool all_cpus;
@@ -2075,11 +2076,12 @@ static void kvm_hv_send_ipi_to_many(struct kvm *kvm, u32 vector, static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) { + struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); + u64 *sparse_banks = hv_vcpu->sparse_banks; struct kvm *kvm = vcpu->kvm; struct hv_send_ipi_ex send_ipi_ex; struct hv_send_ipi send_ipi; u64 valid_bank_mask; - u64 sparse_banks[KVM_HV_MAX_SPARSE_VCPU_SET_BITS]; u32 vector; bool all_cpus;
--
2.35.3