From: Hans-Jörg Höxer <hshoexer@genua.de>
Subject: Re: [EXT] Re: vmm(4)/amd64: reduce use of extern
To: <tech@openbsd.org>
Date: Mon, 28 Apr 2025 15:25:48 +0200

Hi,

On Mon, Apr 28, 2025 at 01:20:15PM +0200, Mark Kettenis wrote:
> > Date: Mon, 28 Apr 2025 12:57:18 +0200
> > From: Hans-Jörg Höxer <hshoexer@genua.de>
> > 
> > Hi,
> > 
> > this diff reduces the use of "extern" in amd64/vmm_machdep.c and related
> > files.  There might be some more low hanging fruits in eg. pmap.c.
> 
> The problem is that <machine/cpu.h> ends up getting included by a lot
> of files (even from userland).  So there is a big risk of namespace
> pollution.  This is somewhat mitigated by #ifdef _KERNEL, but some of
> the userland code in base does do a #define _KERNEL.  It is also
> mitigated by using a cpu_ prefix for the symbol names.

I see and agree.  New approach:  Diff below just deals with
amd64/vmm_machdep.c and varibles declared in dev/vmm.c.  I'd suggest
to declare those in dev/vmm.h.  Future implementations of vmm_machdep.c
eg. for arm64 will likely need those, too.

Take care,
HJ.
----------------------------------------------------------------------------
commit dd3e5f229f00bc357b1121ed56180b8c0a87124d
Author: Hans-Joerg Hoexer <hshoexer@genua.de>
Date:   Mon Apr 28 15:15:07 2025 +0200

    vmm(4)/amd64: reduce use of extern

diff --git a/sys/arch/amd64/amd64/vmm_machdep.c b/sys/arch/amd64/amd64/vmm_machdep.c
index 9b5d56da27b..c9a2f8b73f9 100644
--- a/sys/arch/amd64/amd64/vmm_machdep.c
+++ b/sys/arch/amd64/amd64/vmm_machdep.c
@@ -193,9 +193,6 @@ const struct kmem_pa_mode vmm_kp_contig = {
 	.kp_zero = 1,
 };
 
-extern struct cfdriver vmm_cd;
-extern const struct cfattach vmm_ca;
-
 /*
  * Helper struct to easily get the VMCS field IDs needed in vmread/vmwrite
  * to access the individual fields of the guest segment registers. This
@@ -225,12 +222,6 @@ const struct {
 	  VMCS_GUEST_IA32_TR_AR, VMCS_GUEST_IA32_TR_BASE }
 };
 
-/* Pools for VMs and VCPUs */
-extern struct pool vm_pool;
-extern struct pool vcpu_pool;
-
-extern struct vmm_softc *vmm_softc;
-
 /* IDT information used when populating host state area */
 extern vaddr_t idt_vaddr;
 extern struct gate_descriptor *idt;
diff --git a/sys/dev/vmm/vmm.h b/sys/dev/vmm/vmm.h
index 00cf820c9f1..f27433b9e1b 100644
--- a/sys/dev/vmm/vmm.h
+++ b/sys/dev/vmm/vmm.h
@@ -228,6 +228,12 @@ struct vmm_softc {
 	uint8_t			vpids[512];	/* [p] bitmap of VPID/ASIDs */
 };
 
+extern struct vmm_softc *vmm_softc;
+extern struct pool vm_pool;
+extern struct pool vcpu_pool;
+extern struct cfdriver vmm_cd;
+extern const struct cfattach vmm_ca;
+
 int vmm_probe(struct device *, void *, void *);
 int vmm_activate(struct device *, int);
 void vmm_attach(struct device *, struct device *,  void *);