[PATCH 12/16] KVM: arm64: Don't switch MMU on translation from non-NV context

[Marc Zyngier]

If calling into the AT code from guest EL1, there is no need
to consider any context switch, as we are guaranteed to be
in the correct context.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/at.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
index 76745e81bd9c8..6e767ae3c495a 100644
--- a/arch/arm64/kvm/at.c
+++ b/arch/arm64/kvm/at.c
@@ -1294,7 +1294,7 @@ static u64 __kvm_at_s1e01_fast(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)
 {
 	struct mmu_config config;
 	struct kvm_s2_mmu *mmu;
-	bool fail;
+	bool fail, mmu_cs;
 	u64 par;
 
 	par = SYS_PAR_EL1_F;
@@ -1310,8 +1310,13 @@ static u64 __kvm_at_s1e01_fast(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)
 	 * If HCR_EL2.{E2H,TGE} == {1,1}, the MMU context is already
 	 * the right one (as we trapped from vEL2). If not, save the
 	 * full MMU context.
+	 *
+	 * We are also guaranteed to be in the correct context if
+	 * we're not in a nested VM.
 	 */
-	if (vcpu_el2_e2h_is_set(vcpu) && vcpu_el2_tge_is_set(vcpu))
+	mmu_cs = (vcpu_has_nv(vcpu) &&
+		  !(vcpu_el2_e2h_is_set(vcpu) && vcpu_el2_tge_is_set(vcpu)));
+	if (!mmu_cs)
 		goto skip_mmu_switch;
 
 	/*
@@ -1379,7 +1384,7 @@ static u64 __kvm_at_s1e01_fast(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)
 
 	write_sysreg_hcr(HCR_HOST_VHE_FLAGS);
 
-	if (!(vcpu_el2_e2h_is_set(vcpu) && vcpu_el2_tge_is_set(vcpu)))
+	if (mmu_cs)
 		__mmu_config_restore(&config);
 
 	return par;
-- 
2.39.2