From: Marc Zyngier <marc.zyngier@xxxxxxx>
If trapping FPSIMD in the context of an AArch32 guest, it is critical
to set FPEXC32_EL2.EN to 1 so that the trapping is taken to EL2 and
not EL1.
Conversely, it is just as critical *not* to set FPEXC32_EL2.EN to 1
if we're not going to trap FPSIMD, as we then corrupt the existing
VFP state.
Moving the call to __activate_traps_fpsimd32 to the point where we
know for sure that we are going to trap ensures that we don't set that
bit spuriously.
Fixes: e6b673b741ea ("KVM: arm64: Optimise FPSIMD handling to reduce guest/host thrashing")
Cc: stable@xxxxxxxxxxxxxxx # v4.18
Cc: Dave Martin <dave.martin@xxxxxxx>
Reported-by: Alexander Graf <agraf@xxxxxxx>
Tested-by: Alexander Graf <agraf@xxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxx>
---
arch/arm64/kvm/hyp/switch.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index d496ef579859..ca46153d7915 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -98,8 +98,10 @@ static void activate_traps_vhe(struct kvm_vcpu *vcpu)
val = read_sysreg(cpacr_el1);
val |= CPACR_EL1_TTA;
val &= ~CPACR_EL1_ZEN;
- if (!update_fp_enabled(vcpu))
+ if (!update_fp_enabled(vcpu)) {
val &= ~CPACR_EL1_FPEN;
+ __activate_traps_fpsimd32(vcpu);
+ }
write_sysreg(val, cpacr_el1);
@@ -114,8 +116,10 @@ static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
val = CPTR_EL2_DEFAULT;
val |= CPTR_EL2_TTA | CPTR_EL2_TZ;
- if (!update_fp_enabled(vcpu))
+ if (!update_fp_enabled(vcpu)) {
val |= CPTR_EL2_TFP;
+ __activate_traps_fpsimd32(vcpu);
+ }
write_sysreg(val, cptr_el2);
}
@@ -129,7 +133,6 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN) && (hcr & HCR_VSE))
write_sysreg_s(vcpu->arch.vsesr_el2, SYS_VSESR_EL2);
- __activate_traps_fpsimd32(vcpu);
if (has_vhe())
activate_traps_vhe(vcpu);
else
--
2.18.0
