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KVM: VMX: Track common EPTP for Hyper-V's paravirt TLB flush

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Explicitly track the EPTP that is common to all vCPUs instead of
grabbing vCPU0's EPTP when invoking Hyper-V's paravirt TLB flush.
Tracking the EPTP will allow optimizing the checks when loading a new
EPTP and will also allow dropping ept_pointer_match, e.g. by marking
the common EPTP as invalid.

This also technically fixes a bug where KVM could theoretically flush an
invalid GPA if all vCPUs have an invalid root.  In practice, it's likely
impossible to trigger a remote TLB flush in such a scenario.  In any
case, the superfluous flush is completely benign.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210305183123.3978098-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2021-03-05 10:31:14 -08:00 committed by Paolo Bonzini
parent e83bc09caf
commit a4038ef1aa
2 changed files with 10 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
arch/x86/kvm/vmx/vmx.c
View File

@ -483,12 +483,14 @@ static void check_ept_pointer_match(struct kvm *kvm)
if (!VALID_PAGE(tmp_eptp)) {
tmp_eptp = to_vmx(vcpu)->ept_pointer;
} else if (tmp_eptp != to_vmx(vcpu)->ept_pointer) {
to_kvm_vmx(kvm)->hv_tlb_eptp = INVALID_PAGE;
to_kvm_vmx(kvm)->ept_pointers_match
= EPT_POINTERS_MISMATCH;
return;
}
}
to_kvm_vmx(kvm)->hv_tlb_eptp = tmp_eptp;
to_kvm_vmx(kvm)->ept_pointers_match = EPT_POINTERS_MATCH;
}
@ -501,21 +503,18 @@ static int kvm_fill_hv_flush_list_func(struct hv_guest_mapping_flush_list *flush
range->pages);
}
static inline int __hv_remote_flush_tlb_with_range(struct kvm *kvm,
struct kvm_vcpu *vcpu, struct kvm_tlb_range *range)
static inline int hv_remote_flush_eptp(u64 eptp, struct kvm_tlb_range *range)
{
u64 ept_pointer = to_vmx(vcpu)->ept_pointer;
/*
* FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs address
* of the base of EPT PML4 table, strip off EPT configuration
* information.
*/
if (range)
return hyperv_flush_guest_mapping_range(ept_pointer & PAGE_MASK,
return hyperv_flush_guest_mapping_range(eptp & PAGE_MASK,
kvm_fill_hv_flush_list_func, (void *)range);
else
return hyperv_flush_guest_mapping(ept_pointer & PAGE_MASK);
return hyperv_flush_guest_mapping(eptp & PAGE_MASK);
}
static int hv_remote_flush_tlb_with_range(struct kvm *kvm,
@ -533,12 +532,11 @@ static int hv_remote_flush_tlb_with_range(struct kvm *kvm,
kvm_for_each_vcpu(i, vcpu, kvm) {
/* If ept_pointer is invalid pointer, bypass flush request. */
if (VALID_PAGE(to_vmx(vcpu)->ept_pointer))
ret |= __hv_remote_flush_tlb_with_range(
kvm, vcpu, range);
ret |= hv_remote_flush_eptp(to_vmx(vcpu)->ept_pointer,
range);
}
} else {
ret = __hv_remote_flush_tlb_with_range(kvm,
kvm_get_vcpu(kvm, 0), range);
} else if (VALID_PAGE(to_kvm_vmx(kvm)->hv_tlb_eptp)) {
ret = hv_remote_flush_eptp(to_kvm_vmx(kvm)->hv_tlb_eptp, range);
}
spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);

1
arch/x86/kvm/vmx/vmx.h
View File

@ -351,6 +351,7 @@ struct kvm_vmx {
bool ept_identity_pagetable_done;
gpa_t ept_identity_map_addr;
hpa_t hv_tlb_eptp;
enum ept_pointers_status ept_pointers_match;
spinlock_t ept_pointer_lock;
};