Commit a4038ef1 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

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



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: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210305183123.3978098-3-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent e83bc09c

arch/x86/kvm/vmx/vmx.c

+9 −11
Original line number Original line Diff line number Diff line
@@ -483,12 +483,14 @@ static void check_ept_pointer_match(struct kvm *kvm) 
		if (!VALID_PAGE(tmp_eptp)) {

		if (!VALID_PAGE(tmp_eptp)) {

			tmp_eptp = to_vmx(vcpu)->ept_pointer;

			tmp_eptp = to_vmx(vcpu)->ept_pointer;

		} else if (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

			to_kvm_vmx(kvm)->ept_pointers_match

				= EPT_POINTERS_MISMATCH;

				= EPT_POINTERS_MISMATCH;

			return;

			return;

		}

		}

	}

	}





	to_kvm_vmx(kvm)->hv_tlb_eptp = tmp_eptp;

	to_kvm_vmx(kvm)->ept_pointers_match = EPT_POINTERS_MATCH;

	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);

			range->pages);

}

}





static inline int __hv_remote_flush_tlb_with_range(struct kvm *kvm,

static inline int hv_remote_flush_eptp(u64 eptp, struct kvm_tlb_range *range)

		struct kvm_vcpu *vcpu, struct kvm_tlb_range *range)

{

{

	u64 ept_pointer = to_vmx(vcpu)->ept_pointer;



	/*

	/*

	 * FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs address

	 * FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs address

	 * of the base of EPT PML4 table, strip off EPT configuration

	 * of the base of EPT PML4 table, strip off EPT configuration

	 * information.

	 * information.

	 */

	 */

	if (range)

	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);

				kvm_fill_hv_flush_list_func, (void *)range);

	else

	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,

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) {

		kvm_for_each_vcpu(i, vcpu, kvm) {

			/* If ept_pointer is invalid pointer, bypass flush request. */

			/* If ept_pointer is invalid pointer, bypass flush request. */

			if (VALID_PAGE(to_vmx(vcpu)->ept_pointer))

			if (VALID_PAGE(to_vmx(vcpu)->ept_pointer))

				ret |= __hv_remote_flush_tlb_with_range(

				ret |= hv_remote_flush_eptp(to_vmx(vcpu)->ept_pointer,

					kvm, vcpu, range);

							    range);

		}

		}

	} else {

	} else if (VALID_PAGE(to_kvm_vmx(kvm)->hv_tlb_eptp)) {

		ret = __hv_remote_flush_tlb_with_range(kvm,

		ret = hv_remote_flush_eptp(to_kvm_vmx(kvm)->hv_tlb_eptp, range);

				kvm_get_vcpu(kvm, 0), range);

	}

	}





	spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);

	spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);

arch/x86/kvm/vmx/vmx.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -351,6 +351,7 @@ struct kvm_vmx { 
	bool ept_identity_pagetable_done;

	bool ept_identity_pagetable_done;

	gpa_t ept_identity_map_addr;

	gpa_t ept_identity_map_addr;





	hpa_t hv_tlb_eptp;

	enum ept_pointers_status ept_pointers_match;

	enum ept_pointers_status ept_pointers_match;

	spinlock_t ept_pointer_lock;

	spinlock_t ept_pointer_lock;

};

};