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arm64: KVM: Only force FPEXC32_EL2.EN if trapping FPSIMD

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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: e6b673b741 ("KVM: arm64: Optimise FPSIMD handling to reduce guest/host thrashing")
Cc: stable@vger.kernel.org # v4.18
Cc: Dave Martin <dave.martin@arm.com>
Reported-by: Alexander Graf <agraf@suse.de>
Tested-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
This commit is contained in:
Marc Zyngier 2018-08-23 11:51:43 +01:00 committed by Christoffer Dall
parent 694556d54f
commit 7d14919c0d
1 changed files with 6 additions and 3 deletions
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9
arch/arm64/kvm/hyp/switch.c
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@ -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