arm/arm64: KVM: vgic: Do not save GICH_HCR / ICH_HCR_EL2

The GIC Hypervisor Configuration Register is used to enable
the delivery of virtual interupts to a guest, as well as to
define in which conditions maintenance interrupts are delivered
to the host.

This register doesn't contain any information that we need to
read back (the EOIcount is utterly useless for us).

So let's save ourselves some cycles, and not save it before
writing zero to it.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm/kvm/interrupts_head.S

@@ -412,7 +412,6 @@ vcpu	.req	r0		@ vcpu pointer always in r0
 	add	r11, vcpu, #VCPU_VGIC_CPU
 
 	/* Save all interesting registers */
-	ldr	r3, [r2, #GICH_HCR]
 	ldr	r4, [r2, #GICH_VMCR]
 	ldr	r5, [r2, #GICH_MISR]
 	ldr	r6, [r2, #GICH_EISR0]
@@ -420,7 +419,6 @@ vcpu	.req	r0		@ vcpu pointer always in r0
 	ldr	r8, [r2, #GICH_ELRSR0]
 	ldr	r9, [r2, #GICH_ELRSR1]
 	ldr	r10, [r2, #GICH_APR]
-ARM_BE8(rev	r3, r3	)
 ARM_BE8(rev	r4, r4	)
 ARM_BE8(rev	r5, r5	)
 ARM_BE8(rev	r6, r6	)
@@ -429,7 +427,6 @@ ARM_BE8(rev	r8, r8	)
 ARM_BE8(rev	r9, r9	)
 ARM_BE8(rev	r10, r10	)
 
-	str	r3, [r11, #VGIC_V2_CPU_HCR]
 	str	r4, [r11, #VGIC_V2_CPU_VMCR]
 	str	r5, [r11, #VGIC_V2_CPU_MISR]
 #ifdef CONFIG_CPU_ENDIAN_BE8

arch/arm64/kvm/vgic-v2-switch.S

@@ -47,7 +47,6 @@ __save_vgic_v2_state:
 	add	x3, x0, #VCPU_VGIC_CPU
 
 	/* Save all interesting registers */
-	ldr	w4, [x2, #GICH_HCR]
 	ldr	w5, [x2, #GICH_VMCR]
 	ldr	w6, [x2, #GICH_MISR]
 	ldr	w7, [x2, #GICH_EISR0]
@@ -55,7 +54,6 @@ __save_vgic_v2_state:
 	ldr	w9, [x2, #GICH_ELRSR0]
 	ldr	w10, [x2, #GICH_ELRSR1]
 	ldr	w11, [x2, #GICH_APR]
-CPU_BE(	rev	w4,  w4  )
 CPU_BE(	rev	w5,  w5  )
 CPU_BE(	rev	w6,  w6  )
 CPU_BE(	rev	w7,  w7  )
@@ -64,7 +62,6 @@ CPU_BE(	rev	w9,  w9  )
 CPU_BE(	rev	w10, w10 )
 CPU_BE(	rev	w11, w11 )
 
-	str	w4, [x3, #VGIC_V2_CPU_HCR]
 	str	w5, [x3, #VGIC_V2_CPU_VMCR]
 	str	w6, [x3, #VGIC_V2_CPU_MISR]
 CPU_LE(	str	w7, [x3, #VGIC_V2_CPU_EISR] )

arch/arm64/kvm/vgic-v3-switch.S

@@ -48,13 +48,11 @@
 	dsb	st
 
 	// Save all interesting registers
-	mrs_s	x4, ICH_HCR_EL2
 	mrs_s	x5, ICH_VMCR_EL2
 	mrs_s	x6, ICH_MISR_EL2
 	mrs_s	x7, ICH_EISR_EL2
 	mrs_s	x8, ICH_ELSR_EL2
 
-	str	w4, [x3, #VGIC_V3_CPU_HCR]
 	str	w5, [x3, #VGIC_V3_CPU_VMCR]
 	str	w6, [x3, #VGIC_V3_CPU_MISR]
 	str	w7, [x3, #VGIC_V3_CPU_EISR]