[PATCH v6 19/26] arm64: KVM: Move stashing of x0/x1 into the vector code itself

[Marc Zyngier]

All our useful entry points into the hypervisor are starting by
saving x0 and x1 on the stack. Let's move those into the vectors
by introducing macros that annotate whether a vector is valid or
not, thus indicating whether we want to stash registers or not.

The only drawback is that we now also stash registers for el2_error,
but this should never happen, and we pop them back right at the
start of the handling sequence.

Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
---
 arch/arm64/kvm/hyp/hyp-entry.S | 56 ++++++++++++++++++++++++------------------
 1 file changed, 32 insertions(+), 24 deletions(-)

diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index f36464bd57c5..0f62b5f76aa5 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -55,7 +55,6 @@ ENTRY(__vhe_hyp_call)
 ENDPROC(__vhe_hyp_call)
 
 el1_sync:				// Guest trapped into EL2
-	stp	x0, x1, [sp, #-16]!
 
 alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
 	mrs	x1, esr_el2
@@ -137,18 +136,18 @@ alternative_else_nop_endif
 	b	__guest_exit
 
 el1_irq:
-	stp     x0, x1, [sp, #-16]!
 	ldr	x1, [sp, #16 + 8]
 	mov	x0, #ARM_EXCEPTION_IRQ
 	b	__guest_exit
 
 el1_error:
-	stp     x0, x1, [sp, #-16]!
 	ldr	x1, [sp, #16 + 8]
 	mov	x0, #ARM_EXCEPTION_EL1_SERROR
 	b	__guest_exit
 
 el2_error:
+	ldp	x0, x1, [sp], #16
+
 	/*
 	 * Only two possibilities:
 	 * 1) Either we come from the exit path, having just unmasked
@@ -206,32 +205,41 @@ ENDPROC(\label)
 	invalid_vector	el2h_sync_invalid
 	invalid_vector	el2h_irq_invalid
 	invalid_vector	el2h_fiq_invalid
-	invalid_vector	el1_sync_invalid
-	invalid_vector	el1_irq_invalid
 	invalid_vector	el1_fiq_invalid
 
 	.ltorg
 
 	.align 11
 
+.macro valid_vect target
+	.align 7
+	stp	x0, x1, [sp, #-16]!
+	b	\target
+.endm
+
+.macro invalid_vect target
+	.align 7
+	b	\target
+.endm
+
 ENTRY(__kvm_hyp_vector)
-	ventry	el2t_sync_invalid		// Synchronous EL2t
-	ventry	el2t_irq_invalid		// IRQ EL2t
-	ventry	el2t_fiq_invalid		// FIQ EL2t
-	ventry	el2t_error_invalid		// Error EL2t
-
-	ventry	el2h_sync_invalid		// Synchronous EL2h
-	ventry	el2h_irq_invalid		// IRQ EL2h
-	ventry	el2h_fiq_invalid		// FIQ EL2h
-	ventry	el2_error			// Error EL2h
-
-	ventry	el1_sync			// Synchronous 64-bit EL1
-	ventry	el1_irq				// IRQ 64-bit EL1
-	ventry	el1_fiq_invalid			// FIQ 64-bit EL1
-	ventry	el1_error			// Error 64-bit EL1
-
-	ventry	el1_sync			// Synchronous 32-bit EL1
-	ventry	el1_irq				// IRQ 32-bit EL1
-	ventry	el1_fiq_invalid			// FIQ 32-bit EL1
-	ventry	el1_error			// Error 32-bit EL1
+	invalid_vect	el2t_sync_invalid	// Synchronous EL2t
+	invalid_vect	el2t_irq_invalid	// IRQ EL2t
+	invalid_vect	el2t_fiq_invalid	// FIQ EL2t
+	invalid_vect	el2t_error_invalid	// Error EL2t
+
+	invalid_vect	el2h_sync_invalid	// Synchronous EL2h
+	invalid_vect	el2h_irq_invalid	// IRQ EL2h
+	invalid_vect	el2h_fiq_invalid	// FIQ EL2h
+	valid_vect	el2_error		// Error EL2h
+
+	valid_vect	el1_sync		// Synchronous 64-bit EL1
+	valid_vect	el1_irq			// IRQ 64-bit EL1
+	invalid_vect	el1_fiq_invalid		// FIQ 64-bit EL1
+	valid_vect	el1_error		// Error 64-bit EL1
+
+	valid_vect	el1_sync		// Synchronous 32-bit EL1
+	valid_vect	el1_irq			// IRQ 32-bit EL1
+	invalid_vect	el1_fiq_invalid		// FIQ 32-bit EL1
+	valid_vect	el1_error		// Error 32-bit EL1
 ENDPROC(__kvm_hyp_vector)
-- 
2.14.2