There is no need to enable/disable traps to FP registers on every switch
to/from the VM, because the host kernel does not use this resource
without calling vcpu_put. We can therefore move things around enough
that we still always write FPEXC32_EL2 before programming CPTR_EL2 but
only program these during vcpu load/put.
Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
---
arch/arm64/include/asm/kvm_hyp.h | 3 +++
arch/arm64/kvm/hyp/switch.c | 34 ++++++++++++++++++++++++----------
arch/arm64/kvm/hyp/sysreg-sr.c | 4 ++++
3 files changed, 31 insertions(+), 10 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index 3f54c55..28d5f3c 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -148,6 +148,9 @@ void __fpsimd_save_state(struct user_fpsimd_state *fp_regs);
void __fpsimd_restore_state(struct user_fpsimd_state *fp_regs);
bool __fpsimd_enabled(void);
+void activate_traps_vhe_load(struct kvm_vcpu *vcpu);
+void deactivate_traps_vhe_put(void);
+
u64 __guest_enter(struct kvm_vcpu *vcpu, struct kvm_cpu_context *host_ctxt);
void __noreturn __hyp_do_panic(unsigned long, ...);
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index c587416..09be10f 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -23,22 +23,25 @@
#include <asm/kvm_hyp.h>
#include <asm/fpsimd.h>
-static void __hyp_text __activate_traps_common(struct kvm_vcpu *vcpu)
+static void __hyp_text __activate_traps_fpsimd32(struct kvm_vcpu *vcpu)
{
/*
- * We are about to set CPTR_EL2.TFP to trap all floating point
- * register accesses to EL2, however, the ARM ARM clearly states that
- * traps are only taken to EL2 if the operation would not otherwise
- * trap to EL1. Therefore, always make sure that for 32-bit guests,
- * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
- * If FP/ASIMD is not implemented, FPEXC is UNDEFINED and any access to
- * it will cause an exception.
+ * We are about to trap all floating point register accesses to EL2,
+ * however, traps are only taken to EL2 if the operation would not
+ * otherwise trap to EL1. Therefore, always make sure that for 32-bit
+ * guests, we set FPEXC.EN to prevent traps to EL1, when setting the
+ * TFP bit. If FP/ASIMD is not implemented, FPEXC is UNDEFINED and
+ * any access to it will cause an exception.
*/
if (vcpu_el1_is_32bit(vcpu) && system_supports_fpsimd() &&
!vcpu->arch.guest_vfp_loaded) {
write_sysreg(1 << 30, fpexc32_el2);
isb();
}
+}
+
+static void __hyp_text __activate_traps_common(struct kvm_vcpu *vcpu)
+{
write_sysreg(vcpu->arch.hcr_el2, hcr_el2);
/* Trap on AArch32 cp15 c15 (impdef sysregs) accesses (EL1 or EL0) */
@@ -60,10 +63,12 @@ static void __hyp_text __deactivate_traps_common(void)
write_sysreg(0, pmuserenr_el0);
}
-static void __hyp_text __activate_traps_vhe(struct kvm_vcpu *vcpu)
+void activate_traps_vhe_load(struct kvm_vcpu *vcpu)
{
u64 val;
+ __activate_traps_fpsimd32(vcpu);
+
val = read_sysreg(cpacr_el1);
val |= CPACR_EL1_TTA;
if (vcpu->arch.guest_vfp_loaded)
@@ -71,7 +76,15 @@ static void __hyp_text __activate_traps_vhe(struct kvm_vcpu *vcpu)
else
val &= ~CPACR_EL1_FPEN;
write_sysreg(val, cpacr_el1);
+}
+void deactivate_traps_vhe_put(void)
+{
+ write_sysreg(CPACR_EL1_FPEN, cpacr_el1);
+}
+
+static void __hyp_text __activate_traps_vhe(struct kvm_vcpu *vcpu)
+{
write_sysreg(__kvm_hyp_vector, vbar_el1);
}
@@ -79,6 +92,8 @@ static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
{
u64 val;
+ __activate_traps_fpsimd32(vcpu);
+
val = CPTR_EL2_DEFAULT;
val |= CPTR_EL2_TTA;
if (vcpu->arch.guest_vfp_loaded)
@@ -109,7 +124,6 @@ static void __hyp_text __deactivate_traps_vhe(void)
write_sysreg(mdcr_el2, mdcr_el2);
write_sysreg(HCR_HOST_VHE_FLAGS, hcr_el2);
- write_sysreg(CPACR_EL1_FPEN, cpacr_el1);
write_sysreg(vectors, vbar_el1);
}
diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
index 6ff1ce5..54a4f55 100644
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -242,6 +242,8 @@ void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu)
__sysreg_restore_el1_state(guest_ctxt);
vcpu->arch.sysregs_loaded_on_cpu = true;
+
+ activate_traps_vhe_load(vcpu);
}
/**
@@ -272,6 +274,8 @@ void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu)
if (!has_vhe())
return;
+ deactivate_traps_vhe_put();
+
__sysreg_save_el1_state(guest_ctxt);
__sysreg_save_user_state(guest_ctxt);
__sysreg32_save_state(vcpu);
--
2.9.0
