[PATCH v6 6/6] arm/arm64: KVM: Enable armv8 fp/simd enhanced context switch

[Mario Smarduch]

Enable armv8 enhanced fp/simd context switch. Guest and host registers are only
context switched on first access and vcpu put.

Signed-off-by: Mario Smarduch <m.smarduch at samsung.com>
---
 arch/arm/kvm/arm.c              | 13 +++++++++++--
 arch/arm64/kernel/asm-offsets.c |  1 +
 arch/arm64/kvm/hyp/entry.S      |  1 +
 arch/arm64/kvm/hyp/switch.c     | 26 ++------------------------
 4 files changed, 15 insertions(+), 26 deletions(-)

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index b16ed98..633a208 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -316,10 +316,19 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 {
 	/* If the fp/simd registers are dirty save guest, restore host. */
-	if (vcpu_vfp_isdirty(vcpu))
+	if (vcpu_vfp_isdirty(vcpu)) {
+
 		vcpu_restore_host_vfp_state(vcpu);
 
-	/* Restore host FPEXC trashed in vcpu_load */
+		/*
+		 * For 32bit guest on arm64 save the guest fpexc register
+		 * in EL2 mode.
+		 */
+		if (vcpu_guest_is_32bit(vcpu))
+			vcpu_save_fpexc(vcpu);
+	}
+
+	/* For arm32 restore host FPEXC trashed in vcpu_load. */
 	vcpu_restore_host_fpexc(vcpu);
 
 	/*
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 94090a6..d69145c 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -112,6 +112,7 @@ int main(void)
   DEFINE(VCPU_ESR_EL2,		offsetof(struct kvm_vcpu, arch.fault.esr_el2));
   DEFINE(VCPU_FAR_EL2,		offsetof(struct kvm_vcpu, arch.fault.far_el2));
   DEFINE(VCPU_HPFAR_EL2,	offsetof(struct kvm_vcpu, arch.fault.hpfar_el2));
+  DEFINE(VCPU_CPTR_EL2,		offsetof(struct kvm_vcpu, arch.cptr_el2));
   DEFINE(VCPU_HOST_CONTEXT,	offsetof(struct kvm_vcpu, arch.host_cpu_context));
 #endif
 #ifdef CONFIG_CPU_PM
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index fd0fbe9..ce7e903 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -136,6 +136,7 @@ ENTRY(__fpsimd_guest_restore)
 	isb
 
 	mrs	x3, tpidr_el2
+	str	w2, [x3, #VCPU_CPTR_EL2]
 
 	ldr	x0, [x3, #VCPU_HOST_CONTEXT]
 	kern_hyp_va x0
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index ca8f5a5..962d179 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -19,24 +19,10 @@
 
 static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
 {
-	u64 val;
-
-	/*
-	 * 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.
-	 */
-	val = vcpu->arch.hcr_el2;
-	if (!(val & HCR_RW)) {
-		write_sysreg(1 << 30, fpexc32_el2);
-		isb();
-	}
-	write_sysreg(val, hcr_el2);
+	write_sysreg(vcpu->arch.hcr_el2, hcr_el2);
 	/* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
 	write_sysreg(1 << 15, hstr_el2);
-	write_sysreg(CPTR_EL2_TTA | CPTR_EL2_TFP, cptr_el2);
+	write_sysreg(vcpu->arch.cptr_el2, cptr_el2);
 	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
 }
 
@@ -89,7 +75,6 @@ static int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpu_context *host_ctxt;
 	struct kvm_cpu_context *guest_ctxt;
-	bool fp_enabled;
 	u64 exit_code;
 
 	vcpu = kern_hyp_va(vcpu);
@@ -119,8 +104,6 @@ static int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
 	exit_code = __guest_enter(vcpu, host_ctxt);
 	/* And we're baaack! */
 
-	fp_enabled = __fpsimd_enabled();
-
 	__sysreg_save_state(guest_ctxt);
 	__sysreg32_save_state(vcpu);
 	__timer_save_state(vcpu);
@@ -131,11 +114,6 @@ static int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
 
 	__sysreg_restore_state(host_ctxt);
 
-	if (fp_enabled) {
-		__fpsimd_save_state(&guest_ctxt->gp_regs.fp_regs);
-		__fpsimd_restore_state(&host_ctxt->gp_regs.fp_regs);
-	}
-
 	__debug_save_state(vcpu, kern_hyp_va(vcpu->arch.debug_ptr), guest_ctxt);
 	__debug_cond_restore_host_state(vcpu);
 
-- 
1.9.1