[PATCH v4 00/11] KVM: VMX: Clean up Hyper-V PV TLB flush

[Sean Christopherson]

Clean up KVM's PV TLB flushing when running with EPT on Hyper-V, i.e. as
a nested VMM.  No real goal in mind other than the sole patch in v1, which
is a minor change to avoid a future mixup when TDX also wants to define
.remote_flush_tlb.  Everything else is opportunistic clean up.

NOTE: Based on my NPT+SME bug fix series[*] due to multiple conflicts with
      non-trivial resolutions.

[*] https://lkml.kernel.org/r/20210305011101.3597423-1-seanjc@xxxxxxxxxx


Patch 1 legitimately tested on VMX and SVM (including i386).  Patches 2+
smoke tested by hacking usage of the relevant flows without actually
routing to the Hyper-V hypercalls (partial hack-a-patch below).

-static inline int hv_remote_flush_root_ept(hpa_t root_ept,
+static inline int hv_remote_flush_root_ept(struct kvm *kvm, hpa_t root_ept,
                                           struct kvm_tlb_range *range)
 {
-       if (range)
-               return hyperv_flush_guest_mapping_range(root_ept,
-                               kvm_fill_hv_flush_list_func, (void *)range);
-       else
-               return hyperv_flush_guest_mapping(root_ept);
+       if (range) {
+               kvm_make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH);
+               return 0;
+       }
+
+       return -ENOMEM;
 }
 
 static int hv_remote_flush_tlb_with_range(struct kvm *kvm,
@@ -7753,8 +7754,7 @@ static __init int hardware_setup(void)
                vmx_x86_ops.update_cr8_intercept = NULL;
 
 #if IS_ENABLED(CONFIG_HYPERV)
-       if (ms_hyperv.nested_features & HV_X64_NESTED_GUEST_MAPPING_FLUSH
-           && enable_ept) {
+       if (enable_ept) {
                vmx_x86_ops.tlb_remote_flush = hv_remote_flush_tlb;
                vmx_x86_ops.tlb_remote_flush_with_range =
                                hv_remote_flush_tlb_with_range;

v4: 
  - Rebased to kvm/queue, commit fe5f0041c026 ("KVM/SVM: Move vmenter.S
    exception fixups out of line"), plus the aforementioned series.
  - Don't grab PCID for nested_cr3 (NPT). [Paolo]
  - Collect reviews. [Vitaly]

v3:
  - https://lkml.kernel.org/r/20201027212346.23409-1-sean.j.christopherson@xxxxxxxxx
  - Add a patch to pass the root_hpa instead of pgd to vmx_load_mmu_pgd()
    and retrieve the active PCID only when necessary.  [Vitaly]
  - Selectively collects reviews (skipped a few due to changes). [Vitaly]
  - Explicitly invalidate hv_tlb_eptp instead of leaving it valid when
    the mismatch tracker "knows" it's invalid. [Vitaly]
  - Change the last patch to use "hv_root_ept" instead of "hv_tlb_pgd"
    to better reflect what is actually being tracked.

v2:
  - Rewrite everything.
  - https://lkml.kernel.org/r/20201020215613.8972-1-sean.j.christopherson@xxxxxxxxx

v1: ???

Sean Christopherson (11):
  KVM: x86: Get active PCID only when writing a CR3 value
  KVM: VMX: Track common EPTP for Hyper-V's paravirt TLB flush
  KVM: VMX: Stash kvm_vmx in a local variable for Hyper-V paravirt TLB
    flush
  KVM: VMX: Fold Hyper-V EPTP checking into it's only caller
  KVM: VMX: Do Hyper-V TLB flush iff vCPU's EPTP hasn't been flushed
  KVM: VMX: Invalidate hv_tlb_eptp to denote an EPTP mismatch
  KVM: VMX: Don't invalidate hv_tlb_eptp if the new EPTP matches
  KVM: VMX: Explicitly check for hv_remote_flush_tlb when loading pgd
  KVM: VMX: Define Hyper-V paravirt TLB flush fields iff Hyper-V is
    enabled
  KVM: VMX: Skip additional Hyper-V TLB EPTP flushes if one fails
  KVM: VMX: Track root HPA instead of EPTP for paravirt Hyper-V TLB
    flush

 arch/x86/include/asm/kvm_host.h |   4 +-
 arch/x86/kvm/mmu.h              |   4 +-
 arch/x86/kvm/svm/svm.c          |  10 ++-
 arch/x86/kvm/vmx/vmx.c          | 134 ++++++++++++++++++--------------
 arch/x86/kvm/vmx/vmx.h          |  19 ++---
 5 files changed, 92 insertions(+), 79 deletions(-)

-- 
2.30.1.766.gb4fecdf3b7-goog