KVM: arm64: Invoke FPSIMD context switch trap from C

The conversion of the FPSIMD context switch trap code to C has added
some overhead to calling it, due to the need to save registers that
the procedure call standard defines as caller-saved.

So, perhaps it is no longer worth invoking this trap handler quite
so early.

Instead, we can invoke it from fixup_guest_exit(), with little
likelihood of increasing the overhead much further.

As a convenience, this patch gives __hyp_switch_fpsimd() the same
return semantics fixup_guest_exit().  For now there is no
possibility of a spurious FPSIMD trap, so the function always
returns true, but this allows it to be tail-called with a single
return statement.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 0 insertions, 30 deletions

diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index 40f349bc1079..fad1e164fe48 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -166,33 +166,3 @@ abort_guest_exit_end:
 	orr	x0, x0, x5
 1:	ret
 ENDPROC(__guest_exit)
-
-ENTRY(__fpsimd_guest_restore)
-	// x0: esr
-	// x1: vcpu
-	// x2-x29,lr: vcpu regs
-	// vcpu x0-x1 on the stack
-	stp	x2, x3, [sp, #-144]!
-	stp	x4, x5, [sp, #16]
-	stp	x6, x7, [sp, #32]
-	stp	x8, x9, [sp, #48]
-	stp	x10, x11, [sp, #64]
-	stp	x12, x13, [sp, #80]
-	stp	x14, x15, [sp, #96]
-	stp	x16, x17, [sp, #112]
-	stp	x18, lr, [sp, #128]
-
-	bl	__hyp_switch_fpsimd
-
-	ldp	x4, x5, [sp, #16]
-	ldp	x6, x7, [sp, #32]
-	ldp	x8, x9, [sp, #48]
-	ldp	x10, x11, [sp, #64]
-	ldp	x12, x13, [sp, #80]
-	ldp	x14, x15, [sp, #96]
-	ldp	x16, x17, [sp, #112]
-	ldp	x18, lr, [sp, #128]
-	ldp	x0, x1, [sp, #144]
-	ldp	x2, x3, [sp], #160
-	eret
-ENDPROC(__fpsimd_guest_restore)