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Subject[PATCH RFC 00/19] KVM: x86: hyper-v: Fine-grained TLB flush + Direct TLB flush feature
Currently, KVM handles HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} requests
by flushing the whole VPID and this is sub-optimal. This series introduces
the required mechanism to make handling of these requests more
fine-grained by flushing individual GVAs only (when requested). On this
foundation, "Direct Virtual Flush" Hyper-V feature is implemented. The
feature allows L0 to handle Hyper-V TLB flush hypercalls directly at
L0 without the need to reflect the exit to L1. This has at least two
benefits: reflecting vmexit and the consequent vmenter are avoided + L0
has precise information whether the target vCPU is actually running (and
thus requires a kick).

RFC part:
- The series is poorly tested. I've only smoke-tested WS2019 and Win11+WSL2
on VMX and AMD harware to the point that no immediate issues are observed
on boot. We certainly need something added to selftests/kvm-unit-tests.

Vitaly Kuznetsov (19):
KVM: x86: hyper-v: Resurrect dedicated KVM_REQ_HV_TLB_FLUSH flag
KVM: x86: hyper-v: Introduce TLB flush ring
KVM: x86: hyper-v: Handle HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} calls
KVM: x86: hyper-v: Expose support for extended gva ranges for flush
KVM: x86: Prepare kvm_hv_flush_tlb() to handle L2's GPAs
KVM: x86: hyper-v: Don't use sparse_set_to_vcpu_mask() in
KVM: x86: hyper-v: Create a separate ring for Direct TLB flush
KVM: x86: hyper-v: Use preallocated buffer in 'struct kvm_vcpu_hv'
instead of on-stack 'sparse_banks'
KVM: nVMX: Keep track of hv_vm_id/hv_vp_id when eVMCS is in use
KVM: nSVM: Keep track of Hyper-V hv_vm_id/hv_vp_id
KVM: x86: Introduce .post_hv_direct_flush() nested hook
KVM: x86: hyper-v: Introduce kvm_hv_is_tlb_flush_hcall()
KVM: x86: hyper-v: Direct TLB flush
KVM: x86: hyper-v: Introduce fast kvm_hv_direct_tlb_flush_exposed()
x86/hyperv: Fix 'struct hv_enlightened_vmcs' definition
KVM: nVMX: hyper-v: Direct TLB flush
KVM: x86: KVM_REQ_TLB_FLUSH_CURRENT is a superset of
KVM: nSVM: hyper-v: Direct TLB flush
KVM: x86: Expose Hyper-V Direct TLB flush feature

arch/x86/include/asm/hyperv-tlfs.h | 6 +-
arch/x86/include/asm/kvm_host.h | 30 +++
arch/x86/kvm/Makefile | 3 +-
arch/x86/kvm/hyperv.c | 305 ++++++++++++++++++++++++++---
arch/x86/kvm/hyperv.h | 55 ++++++
arch/x86/kvm/svm/hyperv.c | 18 ++
arch/x86/kvm/svm/hyperv.h | 37 ++++
arch/x86/kvm/svm/nested.c | 25 ++-
arch/x86/kvm/trace.h | 21 +-
arch/x86/kvm/vmx/evmcs.c | 24 +++
arch/x86/kvm/vmx/evmcs.h | 4 +
arch/x86/kvm/vmx/nested.c | 41 +++-
arch/x86/kvm/x86.c | 15 +-
arch/x86/kvm/x86.h | 1 +
14 files changed, 539 insertions(+), 46 deletions(-)
create mode 100644 arch/x86/kvm/svm/hyperv.c


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