[PATCH 2/3] arm: KVM: Implement lazy VFP switching outside of Hyp Mode

[Mario Smarduch]

This patch implements the VFP context switch code called from vcpu_put in
Host KVM. In addition it implements the logic to skip setting a VFP trap if one
is not needed. Also resets the flag if Host KVM switched registers to trap new
guest vfp accesses.


Signed-off-by: Mario Smarduch <m.smarduch at samsung.com>
---
 arch/arm/kvm/interrupts.S |   49 ++++++++++++++++++++++++++++-----------------
 1 file changed, 31 insertions(+), 18 deletions(-)

diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
index 79caf79..0912edd 100644
--- a/arch/arm/kvm/interrupts.S
+++ b/arch/arm/kvm/interrupts.S
@@ -96,6 +96,21 @@ ENTRY(__kvm_flush_vm_context)
 	bx	lr
 ENDPROC(__kvm_flush_vm_context)
 
+ENTRY(__kvm_restore_host_vfp_state)
+	push    {r3-r7}
+
+	mov     r1, #0
+	str     r1, [r0, #VCPU_VFP_SAVED]
+
+	add     r7, r0, #VCPU_VFP_GUEST
+	store_vfp_state r7
+	add     r7, r0, #VCPU_VFP_HOST
+	ldr     r7, [r7]
+	restore_vfp_state r7
+
+	pop     {r3-r7}
+	bx      lr
+ENDPROC(__kvm_restore_host_vfp_state)
 
 /********************************************************************
  *  Hypervisor world-switch code
@@ -131,7 +146,13 @@ ENTRY(__kvm_vcpu_run)
 
 	@ Trap coprocessor CRx accesses
 	set_hstr vmentry
+
+	ldr	r1, [vcpu, #VCPU_VFP_SAVED]
+	cmp	r1, #1
+	beq     skip_guest_vfp_trap
 	set_hcptr vmentry, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))
+skip_guest_vfp_trap:
+
 	set_hdcr vmentry
 
 	@ Write configured ID register into MIDR alias
@@ -173,18 +194,6 @@ __kvm_vcpu_return:
 	set_hcptr vmexit, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))
 
 #ifdef CONFIG_VFPv3
-	@ Save floating point registers we if let guest use them.
-	tst	r2, #(HCPTR_TCP(10) | HCPTR_TCP(11))
-	bne	after_vfp_restore
-
-	@ Switch VFP/NEON hardware state to the host's
-	add	r7, vcpu, #VCPU_VFP_GUEST
-	store_vfp_state r7
-	add	r7, vcpu, #VCPU_VFP_HOST
-	ldr	r7, [r7]
-	restore_vfp_state r7
-
-after_vfp_restore:
 	@ Restore FPEXC_EN which we clobbered on entry
 	pop	{r2}
 	VFPFMXR FPEXC, r2
@@ -363,10 +372,6 @@ hyp_hvc:
 	@ Check syndrome register
 	mrc	p15, 4, r1, c5, c2, 0	@ HSR
 	lsr	r0, r1, #HSR_EC_SHIFT
-#ifdef CONFIG_VFPv3
-	cmp	r0, #HSR_EC_CP_0_13
-	beq	switch_to_guest_vfp
-#endif
 	cmp	r0, #HSR_EC_HVC
 	bne	guest_trap		@ Not HVC instr.
 
@@ -380,7 +385,10 @@ hyp_hvc:
 	cmp     r2, #0
 	bne	guest_trap		@ Guest called HVC
 
-host_switch_to_hyp:
+	/*
+	 * Getting here means host called HVC, we shift parameters and branch
+	 * to Hyp function.
+	 */
 	pop	{r0, r1, r2}
 
 	/* Check for __hyp_get_vectors */
@@ -411,6 +419,10 @@ guest_trap:
 
 	@ Check if we need the fault information
 	lsr	r1, r1, #HSR_EC_SHIFT
+#ifdef CONFIG_VFPv3
+	cmp	r1, #HSR_EC_CP_0_13
+	beq	switch_to_guest_vfp
+#endif
 	cmp	r1, #HSR_EC_IABT
 	mrceq	p15, 4, r2, c6, c0, 2	@ HIFAR
 	beq	2f
@@ -479,11 +491,12 @@ guest_trap:
  */
 #ifdef CONFIG_VFPv3
 switch_to_guest_vfp:
-	load_vcpu			@ Load VCPU pointer to r0
 	push	{r3-r7}
 
 	@ NEON/VFP used.  Turn on VFP access.
 	set_hcptr vmexit, (HCPTR_TCP(10) | HCPTR_TCP(11))
+	mov	r1, #1
+	str	r1, [vcpu, #VCPU_VFP_SAVED]
 
 	@ Switch VFP/NEON hardware state to the guest's
 	add	r7, r0, #VCPU_VFP_HOST
-- 
1.7.9.5