kvm: apic: Flush TLB after APIC mode/address change if VPIDs are in use

This change “kvm: apic: Flush TLB after APIC mode/address change if VPIDs are in use” in Linux kernel is authored by Junaid Shahid <junaids [at] google.com> on Thu Apr 26 13:09:50 2018 -0700.

kvm: apic: Flush TLB after APIC mode/address change if VPIDs are in use

Currently, KVM flushes the TLB after a change to the APIC access page
address or the APIC mode when EPT mode is enabled. However, even in
shadow paging mode, a TLB flush is needed if VPIDs are being used, as
specified in the Intel SDM Section 29.4.5.

So replace vmx_flush_tlb_ept_only() with vmx_flush_tlb(), which will
flush if either EPT or VPIDs are in use.

Signed-off-by: Junaid Shahid <junaids@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

This Linux change may have been applied to various maintained Linux releases and you can find Linux releases including commit a468f2d.

There are 14 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 arch/x86/kvm/vmx.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index aa66ccd..c766880 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4544,12 +4544,6 @@ static void vmx_flush_tlb(struct kvm_vcpu *vcpu, bool invalidate_gpa)
 	__vmx_flush_tlb(vcpu, to_vmx(vcpu)->vpid, invalidate_gpa);
 }
 
-static void vmx_flush_tlb_ept_only(struct kvm_vcpu *vcpu)
-{
-	if (enable_ept)
-		vmx_flush_tlb(vcpu, true);
-}
-
 static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu)
 {
 	ulong cr0_guest_owned_bits = vcpu->arch.cr0_guest_owned_bits;
@@ -9278,7 +9272,7 @@ static void vmx_set_virtual_x2apic_mode(struct kvm_vcpu *vcpu, bool set)
 	} else {
 		sec_exec_control &= ~SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE;
 		sec_exec_control |= SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
-		vmx_flush_tlb_ept_only(vcpu);
+		vmx_flush_tlb(vcpu, true);
 	}
 	vmcs_write32(SECONDARY_VM_EXEC_CONTROL, sec_exec_control);
 
@@ -9306,7 +9300,7 @@ static void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu, hpa_t hpa)
 	    !nested_cpu_has2(get_vmcs12(&vmx->vcpu),
 			     SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES)) {
 		vmcs_write64(APIC_ACCESS_ADDR, hpa);
-		vmx_flush_tlb_ept_only(vcpu);
+		vmx_flush_tlb(vcpu, true);
 	}
 }
 
@@ -11220,7 +11214,7 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 		}
 	} else if (nested_cpu_has2(vmcs12,
 				   SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES)) {
-		vmx_flush_tlb_ept_only(vcpu);
+		vmx_flush_tlb(vcpu, true);
 	}
 
 	/*
@@ -12073,7 +12067,7 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
 	} else if (!nested_cpu_has_ept(vmcs12) &&
 		   nested_cpu_has2(vmcs12,
 				   SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES)) {
-		vmx_flush_tlb_ept_only(vcpu);
+		vmx_flush_tlb(vcpu, true);
 	}
 
 	/* This is needed for same reason as it was needed in prepare_vmcs02 */

The commit for this change in Linux stable tree is a468f2d (patch).

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