[Xen-devel] [PATCH 02/24] xen/arm: hypercalls

On Fri, 27 Jul 2012, Ian Campbell wrote:

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Should this comment be by 'privcmd_call'?

When we add a 5 argument hypercall I suppose we'll see the required
push/pop of r4 added to this macro too.

For performance and simplicity I would add a second macro that push/pop
r4, only required for hypercalls with more than 4 arguments.

For clarity / documentation purposes it might actually be worthwhile to
define all of HYPERCALL{0,1,2,3,4} even if the {0,1,2,3} cases are all
just:
        #define HYPERCALL0(x) HYPERCALL_SIMPLE(x)

I agree

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+#define HYPERCALL(hypercall)			\
+ENTRY(HYPERVISOR_##hypercall)			\
+	mov r12, #__HYPERVISOR_##hypercall;	\
+	xen_hvc;							\
+	mov pc, lr;							\
+ENDPROC(HYPERVISOR_##hypercall)
+
+                .text
+
+HYPERCALL(xen_version);
+HYPERCALL(console_io);
+HYPERCALL(grant_table_op);
+HYPERCALL(sched_op);
+HYPERCALL(event_channel_op);
+HYPERCALL(hvm_op);
+HYPERCALL(memory_op);
+HYPERCALL(physdev_op);
+
+ENTRY(privcmd_call)
+	stmdb	sp!, {r4}
+	mov r12, r0
+	mov r0, r1
+	mov r1, r2
+	mov r2, r3
+	ldr r3, [sp, #8]
+	ldr r4, [sp, #4]
+	xen_hvc
+	pop {r4}

Why not ldmdb for symmetry?

Yep, I can do that.

Actually it is just ldm or ldmia